Employment 1. Surgical Instruments. Primary Surgical Technique. Topographical Anatomy and Operative Surgery of Cerebral Parts of the Head.
MAJOR SURGICAL INSTRUMENTS AND EQUIPMENT OF SURGICAL
BLOCK
GENERAL
APPARATUS, EQUIPMENT
II set, apparatus, instrument, device, gear
III. to switch on apparatus/ device
to switch off apparatus/device
to adjust apparatus/device
SET, DEVICE, APPARATUS, INSTRUMENT, GEAR
II. adjustment of an instrument
reading(s)
finger of a device
scale of an apparatus zero [of an apparatus scale]
INSTRUMENT
fenestrated instrument
pointed instrument
sharp instrument
cutting instrument
blunt instrument
blunt-ended instrument
surgical instrument
II. hold up of an instrument
lock of an instrument
teeth of the lock
tip of an instrument
fine tip of an instrument
set of instruments
nozzle of an instrument
slit of an instrument
blade of an instrument
handle of an instrument
III to hand an instrument
to be ready with an instrument,
to get an instrument prepared
GENERAL INSTRUMENTS
INSTRUMENT(S) TO ARREST BLEEDING
S. forceps, clamp Blalock’s clamp electrocoagulator
FORCEPS, CLAMP
curved hemostatic forceps
straight hemostatic forceps
II. Bilroth’s hemostatic forceps
curved Bilroth’s hemostatic forceps
straight Bilroth’s hemostatic forceps
Hopfner’s forceps
Kocher’s clamp
curved Kocher’s clamp straight Kocher’s clamp
Luer’s forceps
Miculicz clamp
hemostatic “mosquito” forceps
curved hemostatic “mosquito” forceps
straight hemostatic “mosquito” forceps
Pean’s forceps
Hartmann’s forceps
Halstead’s forceps
III.to clamp a vessel, to apply/place a clamp [on a vessel] to take/remove a clamp off[a vessel]
to slip off (of a clamp)
INSTRUMENT(S) FOR PARTING TISSUE, INSTRUMENT(S) FOR DIVIDING TISSUE, INSTRU MENTS) FOR SEPARATING TISSUE
S. scissors, shears, clippers knife, scalpel, lancet
SCISSORS, SHEARS, CLIPPERS
I. rib-cutting forceps
eye/ophthalmic scissors
eye curved scissors
curved scissors
pointed scissors
straight scissors
blood vessel scissors
blunt scissors
surgical scissors
II. dissecting scissors for deep work
Cooper’s scissors
Richter’s scissors
III. to cut with scissors
KNIFE, SCALPEL, LANCET
bellied scalpel,
general operating knife
ophthalmic scalpel
cryoscalpel
laser scalpel
sharp-pointed scalpel
resection scalpel/knife
dental scalpel
II. belly of a scalpel
scalpel blade
scalpel blade for single use
“kitchen-knife” position of a scalpel
“pen-grip” position of a scalpel
“fiddlestick” position of a scalpel
scalpel with a removable blade
to cut with a scalpel
to sharpen a knife
INSTRUMENT(S) FOR SUTURING TISSUE
S. needle
needle-holder, needle carrier
Michel clip (s)
NEEDLE
I atraumatic needle
large (small )pricking needle)
round pricking needle
ligature needle
Dechamp’s needle
straight needle
cutting needle
curved cutting needle
fine/narrow needle
surgeon’s/suture needle
II. suture needle
needle’s eye
III.to thread a needle
to pierce the skin (tissue),
to needle the skin (tissue),
to insert needle through the skin (tissue)
SURGEON’S NEEDLE, SUTURE NEEDLE
noninjuring suture needle
surgeon’s circle needle
intestinal suture needle
skin suture needle
NEEDLE HOLDER, NEEDLE CARRIER
ophthalmic needle-holder
deep-cavity needle-holder
Mathieu’s needle-holder
Troyanov’s needle-holder
MICHEL CLIP(S)
II. Michel clips remover
S. Michel clips box
FIXATION INSTRUMENT. ACCESSORY INSTRUMENT
S. towel clip
Miculicz clamp
catheter, director, probe,
tube
packer, dressing forceps
retractor (s), hook(s)
Buiallsky’s spatula
forceps
CATHETER, DIRECTOR, PROBE, TUBE
I grooved probe
bulbous-end probe
II Kocher’s probe
PACKER, DRESSING FORCEPS
I.curved packer
straight packer
RETRACTOR, HOOK
sharp single-toothed retractor
surgical hook/retractor
SURGICAL HOOK, SURGICAL RETRACTOR
sharp (blunt) pronged Surgical retractor
S-shaped laminar surgical hook by Farabeuf, plate surgical retractor
FORCEPS
ophthalmic forceps
pronged-tenaculum forceps
curved forceps
hemostatic forceps
fenestrated forceps
straight forceps
[dressing] thumb forceps
SYRINGE
I.combined /glass-and-metal syringe
disposable/one piece syringe
sectional/non-disposable syringe
glass Luer’s syringe
II.syringe needle
plunger of a syringe
automatic syringe
Janet’s syringe
continuous-action syringe syringe with a three way tap
“Record” type syringe
III.to take a syringe apart
SPECIAL SURGICAL INSTRUMENTS
INSTRUMENT(S) FOR AMPUTATION OF AN EXTREMITY
S. bone-cutting forceps
bone-holding forceps
knife
saw
raspatory
retractor
BONECUTTING FORCEPS
Liston’s bone cutting forceps
Luer’s forceps
KNIFE
large (small) amputating knife (amputating knife of middle size)
bellied excision knife
surgery/operating knife
SAW
hand type bone saw, dissecting blade saw
thread saw
bow-type bone saw
II frame of a saw
III to saw
RASPATORY, RASP
I curved rasp of Farabeuf
straight rasp of Farabeuf
INSTRUMENT(S) EMPLOYED IN [PERFORMING] GYNECOLOGICAL AND OBSTETRICAL OPERATIONS
S. vacuum extractor
vaginal speculum
bivalve vaginal speculum
spoon-shaped vaginal
speculum
Braun’s decapitation hook
Blot’s lanceolated perforator
Braun’s cranioclast curette for uterine scraping
uterine probe
metreurynter, cervical dilator
umbilical cord knife, knife for umbilical cord dissection
embryotomy scissors
uterine dilator by Hegar
forceps
FORCEPS
obstetrical forceps
Lazarevitch’s forceps
Negel’s forceps
Palfyn’s forceps
Simpson-Fenomenov’s forceps
Chamberlain’s forceps
craniodermal forceps
bone obstetrical forceps,
cranioclast
ovarian forceps
fenestrated/ovum forceps
cavity forceps
bullet forceps
INSTRUMENT(S) FOR [PERFORMING] NEUROSURGERY OPERATIONS
S. automatic dilator/retractor by Adson
automatic dilator/retractor by Jansen
dissector
cannula for brain puncture
Dahlgren’s forceps
Luer’s forceps
neurosurgical spatula
neurosurgical clips
neurosurgical scissors
brain forceps
scissors for dissecting dura mater encephali
fenestrated forceps for removal of tumour/mass
wire file/chain saw by Gigli
wire file/chain saw by Olivecrona
trepan
TREPAN
electrotrepan
S. lancet-shaped cutter
circular-shaped cutter
INSTRUMENT(S) FOR OPERATION ON THE THORACIC WALL AND THORACIC ORGANS / VISCERA
S. apparatus for suturing the root of the lung
apparatus for suturing major vessels
apparatus for suturing/closure of a bronchial stump
apparatus for suturing lung/ pulmonary tissue
heart-lung apparatus
broncho-retractor
bougie
dilator
Luer’s clamp/forceps
Liston’s type cutting forceps with double mechanism
wire speculum
first-rib rasp
Doyen’s rib-cutting shears
Doyen’s rib rasp
pace-maker
thoracic dilator/retractor
BOUGIE
I. hollow bougie
X-ray-contrast bougie
elastic bougie
II.to introduce/pass in a bougie (into the esophagus)
DILATOR
I. aortic dilator
two-paddle dilator
mitral dilator
three-paddle dilator
II. dilator of Brock’s type
dilator of Dubost’s type
dilator of
dilator of Tubes’s type
INSTRUMENT(S) FOR [PERFORMING] OPERATIONS ON BONES
S. chisel, scoop, gouge
[bone] gouge
chisel
drill for bone-drilling
brace
Volkmann’s small spoon
metal plates for osteosynthesis
metal screws for osteosynthesis
hammer, mallet
sequestral forceps
three-flange nail for osteosynthesis
[joint-] pin/sprig for osteosynthesis
HAMMER, MALLET
I. wooden hammer
metal mallet
surgical mallet
INSTRUMENT(S) FOR OPERATIONS ON ABDOMINAL CAVITY ORGANS
S. apparatus for applying gastrointestinal anastomosis
apparatus for applying esophagointestinal gastric anastomosis
apparatus for closure of a stomach stump
Miculicz clamp
abdominal retractor
liver retractor
intestinal clamp
metal hepatic bougie
retractor, dilator
troc[h]ar
surgical spatula by Reverdin
APPARATUS FOR CLOSURE OF A STOMACH STUMP
II. staples, clips
pusher of clips in the apparatus
III. to fill in/set in/load a suturing apparatus with clips
INTESTINAL CLAMP
non-crushing/spring clamp
S. crushing forceps, constrictor, Payr clamp
III. to apply an intestinal clamp (constrictor), to place [an intestinal] clamp (constrictor)
to remove [an intestinal] clamp (constrictor), to take off [an intestinal] clamp (constrictor)
RETRACTOR, DILATOR
screw-type retractor
lock retractor
frame retractor
yard retractor
II. self-retaining retractor of Miculicz [type]
III. to pull a retractor apart
TROC[H]AR
I. curved troc[h]ar
straight troc[h]a’r
II.stylet of a troc[h]ar
INSTRUMENT(S) FOR [PERFORMING] OPERATIONS ON KIDNEYS AND URINOEXCRETORYWAYS
S. bougie
Fyodorov’s forceps
Levkovitch curved forceps catheter
lithotriptor
spoon-shaped forceps
scoop (s) for extraction of stones from the [urinary] bladder
kidney retractor
guide for retrograde insertion of a catheter
urinary bladder speculum urinary bladder retractor
resectoscope
cystoscope
extractor for removal of stones from the ureter
BOUGIE
Guvon’s bougie
female straight urethral bougie
tapered bougie
metal bougie
male curved urethral bougie
threadlike bougie by Le Fort
threadlike bougie
urethral bougie
urethral bougie-probe,
stone searcher
CATHETER
I. temporary/non-indwelling catheter
bulbous catheter
female urethral catheter
metal catheter
urethral catheter
male urethral catheter
loop-shaped/ansiform Zeiss catheter, loop-catheter
permanent/indwelling catheter
rubber catheter
II. Nelaton’s catheter
Malecot’s catheter
Pezzer’s catheter
Pomerantsev-Foley’s catheter
two-way catheter
Thiemann’s Catheter
CYSTOSCOPE
I. operation cystoscope
washing/evacuation/irrigation cystoscope
observation cystoscope
battery operated cystoscope
II.cystoscopic lamp
cystoscope-lithotriptor,
cystolithotriptor
EXTRACTOR FOR REMOVAL OF STONES FROM THE URETER
I. basket/ Dormia’s extractor
loop-like/Zeiss extractor
INSTRUMENT(S) USED IN OPERATIONS ON RECTUM
S. fenestrated hemorrhoidal forceps
fenestrated Luer’s forceps
rectal speculum
proctoscope
INSTRUMENT(S) FOR PERFORMING TRACHEOSTOMY
S. single-toothed sharp
tenaculum/retractor/hook tracheal dilator of Laborde
tracheal dilator of Troussean
tracheostomy tube
internal (external) cannula of the tracheostomy tube
tracheostomy tube with an inflated cuff
ANESTHESIA TECHNIQUES
Anesthesia techniques vary according to the procedure, the surgeon, the patient, the anesthesiologist, and the surgery center’s past experiences. The technique itself is not as important as the drugs and dosages employed. Each surgical center must provide the same standards of care for delivery of anesthesia, monitoring, and resuscitation as those provided for inpatients. Minimal monitoring should include a precordial or esophageal stethoscope, blood pressure cuff, continuous electrocardiograph display, temperature probe, and measure of inspired oxygen concentration. Pulse oximetry may soon be the standard of care in all operating suites, as it has proved valuable not only in general anesthetic cases, but in local and regional anesthesia as well.
LOCAL AND REGIONAL ANESTHESIA
Local Anesthetic Agents. Local anesthetics produce their effect by interfering with the initial step in the excitation-conduction process iervous tissue by decreasing the rate and degree of depolarization without altering the resting potential, threshold potential, or repolarization phase. When the degree of depolarization fails to reach threshold potential, a propagated action fails to develop and nerve conduction is blocked. The receptor site for local anesthetic agents is believed to reside in the nerve membrane. However, the specific receptor location varies according to the type of local anesthetic agent employed. Local anesthetic agents are classified according to their chemical structure. The two major groups are those containing either an ester or an amide link between their aromatic portion and the intermediate chain. The ami-noesters include cocaine, procaine, tetracaine, and chloroprocaine. The aminoamides include lidocaine, mepivacaine, prilocaine, bupivacaine, and etidocaine. The basic differences between the ester and amide compounds reside in the manner in which they are metabolized and in their allergic potential. The ester agents are hydrolyzed in the plasma by pseudocholinesterase, whereas the amide agents undergo enzymatic degradation in the liver. Para-aminobenzoic acid, one of the metabolites formed from the hydrolysis of esterlike compounds, is capable of inducing allergic reactions in a small percentage of the population. The amide drugs are not metabolized to para-aminobenzoic acid, and reports of allergic phenomena are rare. On the basis of differences in anesthetic potency and duration of action, it is possible to classify the clinically useful injectable local anesthetic compounds into three categories:
Group I—agents of low anesthetic potency and short duration of action (procaine and chloroprocaine).
Group II—agents of intermediate anesthetic potency and intermediate duration of action (lidocaine, mepivacaine, prilocaine).
Group III—agents of high anesthetic potency and long duration of action (tetracaine, bupivacaine, etidocaine). These agents are rarely used for ambulatory anesthesia.
Local Infiltration Anesthesia
Infiltration anesthesia involves administration of a local anesthetic agent into an extra-vascular space in or around the operative site and diffusion to the nerve endings, where excitation is inhibited. Onset of action is almost immediate for all agents following intradermal or subcutaneous administration. The concentration and volume of local anesthetic required for adequate infiltration anesthesia depend on the extent of the area to be anesthetized and the expected duration of the surgical procedure. Epinephrine may be added to prolong the effect of infiltration anesthesia. It should be used in concentrations no higher than 1:200,000, and its use is contraindicated ierve blocks of the hands, feet, and digits, when blood supply to the area may already be compromised by the presence of peripheral vascular disease. The most commonly used drugs for infiltration anesthesia include 1% to 2% procaine, 0.5% to 1% lidocaine, 2% chloroprocaine, 0.5% to 1% mepivacaine, and 1% prilocaine. Refer to Table 3-1 for a summary of recommended dosages and durations.9 The surgeon and scrub nurse must be meticulous in accounting for the total amount of local anesthetic administered in order to avoid overdose. The infiltration is generally done by the surgeon with or without monitored anesthesia care (“stand-by”). Complex or extremely anxious patients are better managed with an anesthesiologist monitoring the patient’s vital signs and administering supplementary drugs. In the event that intraoperative problems demand general anesthesia, the anesthesiologist is already present and is not called to treat a patient with whom he is unfamiliar.
Premedication for local anesthesia patients may be useful in allaying anxiety and reducing the pain of injection. If given orally, the medication must have adequate time to take effect before the procedure. A preferable route is to titrate the drug in small doses to the desired effect to avoid oversedation, thus resulting in prolonged postoperative recovery. The ultra-short-acting barbiturates in sub-anesthetic doses are well suited for producing temporary obtundation of consciousness during a painful local anesthetic injection, such as retrobulbar block. Thiopental (25 mg to 50 mg). or methohexital (10 mg to 20 mg) given intravenously may be very useful for this purpose. Caution must be exercised in the care of all j patients, particularly the elderly, who must be monitored closely for signs of respiratory and cardiovascular depression.
Field Block Anesthesia Field block is accomplished by injecting a wall of anesthetic solution across the path of i the nerves supplying an operative field. In the majority of cases the layer of soft tissue in which the nerves are situated is injected. The anesthesia produced by a field block is generally of longer duration than that obtained from local infiltration. Another advantage of field block is the absence of edema and distortion of the anatomic landmarks along the line of incision.
Intravenous Regional Anesthesia Intravenous regional anesthesia involves t the intravenous administration of local anesthetic into a tourniqueted limb.
Figure. Field block for superficial surgery. (A) Intradermal wheals are raised to circumscribe a lipoma, followed by (B) subcutaneous infiltration to surround the surgical specimen.
Calibration of an occlusive double pneumatic tourniquet is of great importance, in order to prevent leakage of the local anesthetic solution, loss of anesthesia, and possible systemic toxicity. Exsan-guination of the limb should be accomplished by elevation and wrapping, distal to proximal, with an Esmarch bandage. One can also accomplish exsanguination by elevating the limb for 5 minutes. Prior to exsanguination, an intravenous catheter should be inserted in a distal vein. After exsanguination has been accomplished, the proximal tourniquet cuff should be inflated to 100 mm Hg above systolic blood pressure. Local anesthetic is then injected into the intravenous catheter when the bandage is removed. Commonly, 40 ml of 0.5% lidocaine has been found to give satisfactory analgesia for the upper extremity, but volumes as large as 75 ml to 100 ml of dilute anesthetic solution, 0.25% to 0.35% lidocaine, may be required for the lower extremity. Children have been successfully treated with intravenous regional anesthesia using 3 mg/kg to 5 mg/kg of 0.25% to 0.5% lidocaine. The proximal cuff should remain inflated for 15 to 20 minutes to allow for adequate tissue binding of the anesthetic drug. The distal tourniquet is then inflated, followed by deflation of the proximal cuff. At the conclusion of the surgery intermittent tourniquet release is advocated in 10- to 15-second intervals, in order to decrease peak concentrations of local anesthetic in the systemic circulation.
Minor Nerve Blocks
Minor nerve blocks are defined as procedures involving single nerve entities, such as the ulnar or radial nerves at the wrist and the anterior or posterior tibial nerves at the ankle. These can be quite useful for superficial procedures of the extremities.
Major Nerve Blocks
Major nerve blocks consist of those procedures in which two or more distinct nerves or a nerve plexus are blocked. For example, a brachial plexus block at the axilla is commonly used for operations of the hand, forearm, and distal part of the arm. A flooding technique is used for brachial plexus block that involves the use of larger volumes of local anesthetic (up to 40 ml) injected within the brachial plexus sheath
Equipment for anesthesia
Regional or local anesthesia techniques can be performed with almost any syringe and needle. Their success depends more on the skill of the operator than on the quality of the instrument. Nevertheless, there are differences in equipment that make some devices more effective than others and, in experienced hands, can optimize the performance of regional techniques.
General Principles Equipment for regional blocks is usually stocked in prepared sterile trays. Trays should include skin-preparation swabs, drapes, needles, syringes, solution cups, and a sterility indicator. The choice of equipment will be dictated by the specific blocks attempted and by personal preference, but some general comments are warranted.
Disposable Versus Reusable Equipment Disposable versus reusable equipment is one of the first considerations. Reusable block trays allow maximum flexibility in choosing specific needles, syringes, and catheters. They allow for the purchase of products that are manufactured to more exact specifications than those usually found in disposable trays For example, glass syringes machined to critically fine tolerances provide a finer appreciation of resistance to injection than less-expensive plastic or one-time-use glass products. However, reusable trays represent a significant initial capital investment and require additional technician time to maintain. Because the trays must be restocked, cleaned, sterilized, and stored, personnel expenses must be considered in comparing the cost to that of disposable equipment Disposable trays have improved considerably owing to competition among manufacturers and an increased volume of use. The quality of equipment has improved, and the willingness of the manufacturers to “customize” trays to the needs of individual institutions is more widespread. Disposable trays offer ease and convenience to most low- to medium-volume users and greatly simplify the demands on anesthesia technicians. They also remove the burden of sterilization from the local department or hospital (although not the responsibility of checking for sterility). The concern for sterility has increased in the era of HIV and hepatitis.
In general, the choice between reusable and disposable equipment is based on the volume of regional techniques performed. In a small department, the disposable trays are quite cost effective. In a larger institution or in a group with a heavy emphasis on regional techniques, the desire for quality equipment and the volume involved may well justify the expense of reusable regional trays and the required technician support.
Sterilization Sterilization of equipment is essential. Presterilized disposable trays eliminate some of this burden, but reusable equipment must be both cleaned and sterilized between uses. Cleaning must be performed vigorously and adequately because no sterilization technique is capable of completely eliminating bacterial contamination in the presence of heavy soiling with organic material. The cleaning process begins at the time of use. Needles and syringes should be rinsed immediately or placed in cold water. Drying of blood or other fluids makes later cleaning more difficult. Meticulous, thorough cleaning and rinsing with cold water are the preferred cleaning method (hot water is more likely to cause coagulation of any blood proteins and impede their removal). Detergents are not desirable for cleaning reusable needles and syringes because of the chance of chemical contamination of local anesthetic solutions from residual cleansing agents left on the syringe or needle. If a needle or syringe is heavily soiled, flushing with a 3% hydrogen peroxide solution is an acceptable adjunct to the cold rinse Significant bacterial or viral contamination is removed by heat sterilization at 121 °C or above for 20 minutes (steam under pressure) This autoclaving technique will usually eliminate even the hardiest bacterial endospores, as well as the less hardy HIV and hepatitis viruses and bacteria and fungal spores. Appropriate indicators of adequate heat exposure must be placed both in the center of each sterilized packet and on the outside. Plastic and rubber will not tolerate heat treatment and must be sterilized with ethylene oxide gas exposure. Precleaning is again essential. A long period of aeration is required to remove residual gas. A different indicator strip is used to document sterility. Disposable trays usually have such an indicator in their central compartment. This must be checked before using the tray. Local anesthetic drugs are usually added to the trays after they are opened because the choice of drug may vary. Added drugs, needles, or other equipment also must be wrapped sterilely and handled in an aseptic manner. Although amino-amide local anesthetics can be resterilized, there is some concern about chemical stability with repeated exposures to high heat, so resterilization is simply avoided in many institutions. Epinephrine is known to discolor after exposure to heat, light, or air and thus is generally not resterilized once a sterile packet is opened. If discoloration occurs, the solution should be discarded.
Skin Preparation Skin preparation (asepsis) also requires meticulous attention. The current standard solution is an iodophor preparation, also termed povidone-iodine. The activity of this solution is based on the release of free iodine, which is dependent on the water dilution of the solution. Careful adherence to the manufacturer’s instructions for dilution and use is important. These are “contact” preparations,- that is, they do not require scrubbing or prolonged contact to remove microorganisms. Unlike previous iodine-alcohol solutions, these preparations are not likely to burn tissues, although excessive quantities in body folds can cause irritation. A few patients are truly allergic to topical iodine preparations and require alternative solutions. Hibiclens is a detergent that requires scrubbing and longer contact time and must be wiped from the skin before insertion of needles. Isopropyl alcohol (70%) is a third satisfactory alternative as a skin preparation, and it does not require scrubbing.
Regardless of the agent used, total sterility of the skin is rarely achieved, and careful attention to aseptic technique is needed. A wide area should be prepped, and sterile towels should be placed on the skin to extend the working field. Although iodophor solutions are generally not toxic to tissues, care should be takeot to contaminate any local anesthetic solution with prep solution, and excess prep solution should be wiped off the skin before insertion of the needle or introducer. Avoid colorless prep solutions because of the serious hazard of potential unrecognized contamination of anesthetic solutions. Although syringes are generally considered only as carrying instruments for the local anesthetics, their features are important. The resistance between the barrel and the piston is critical when using the “loss of resistance” technique for identifying the epidural space. Here, glass syringes have been superior to most plastic material in allowing free movement. Some new lubrication techniques have produced plastic products with low friction, but generally the disposable products rely on a gasket to provide a seal, which gives firm resistance in the movement of the piston and will obscure changes in resistance to injection as the needle is advanced. Glass syringes have the disadvantage that a small amount of powder from sterile gloves can cause the piston to stick in the barrel, but generally these syringes provide better appreciation of
resistance
.
The Three-Ring (“Control”) Syringe
This adaptation to the plunger of a standard 10-cc syringe allows greater control of injection, easier aspiration, and the opportunity to refill the syringe with one hand. Plastic adapters are available for disposable syringes as demonstrated; glass syringes are supplied with a metal plunger and ring attached.
The size of the syringe also affects performance. The smallest syringes (1 cc) give the greatest accuracy in measurement, as is required in adding epinephrine to the anesthetic solution. A small-diameter (3-cc) syringe gives a better feel of resistance during epidural insertion but is impractical for injection of large volumes. For injection, a 10-cc syringe is most comfortably held in the hand; larger syringes are heavy and bulky and usually require two hands for good control. They do not allow the fine control needed for seeking paresthesias. Disconnecting and reconnecting the needle also can be awkward with large syringes if one hand is occupied in fixing the needle in place on the nerve. Larger syringes also add more weight and are more likely to cause an unwanted advancement of the needle. A 10-cc syringe appears to be a practical compromise. It is inconvenient to refill frequently, but use of a 10-cc syringe limits the quantity injected at any one time and thus serves to encourage incremental injection of large volumes of local anesthetic. If a larger syringe (20 or 30 cc) is used, it is desirable to avoid direct connection to the needle by using a short length of flexible intravenous tubing as a connector. This allows for finer control of the needle, but it usually requires an assistant to handle aspiration and injection with the syringe. A three-ring adapter is useful on the 10-cc syringe [control syringe, Fig). It allows greater control in injecting solution and also allows the solo operator to refill the syringe from a local anesthetic cup with one hand while holding the needle in place in the patient with the other. These adapters are available on plastic as well as glass syringes. The connection to the hub of the needle can affect the ease of fixation of the needle. The Luer-Lok adapter, which screws tightly onto the matching needle hub, does not require forceful friction to provide a seal and thus is less likely to cause unwanted movement of the needle when attaching the syringe. This coupling also provides a connection less likely to leak on injection. A tight seal is critical when using resistance to identify the epidural space. In many institutions, the ideal tray would thus have glass Luer-Lok syringes in l-,3-, and 10-cc sizes with a three-ring adapter on the latter Although local infiltration can be performed with almost any needle, special adaptations can facilitate success with regional techniques.
Regional-Block Needles Regional-block needles are often inserted deep into tissue. All needles carry a risk of breaking off during injection, and they may be lost below the skin. Breakage usually occurs between the shaft and hub. A security bead on the shaft 3 to 6 mm from the hub will prevent the broken end from retracting below the skin and allow easy retrieval of brokeeedles.
Conventional sharp-bevel needles have a greater tendency to be associated with nerve damage The incidence of injury may be less with shorter-bevel needles (16 versus 12 degrees) (The short-bevel needle may offer more resistance to advancement but is less traumatic to nerves. Although there has not been a large prospective study documenting the advantages of the short bevel , this has become a standard needle for peripheral nerve block injections.
The gauge employed is a compromise between ease of injection and discomfort caused. Smaller needles (25 to 32 gauge) are best for skin infiltration because their insertion is less uncomfortable. The 23-gauge size is suitable for superficial blocks, such as axillary or intercostals on thin patients. A larger, more rigid shaft is usually required for any deeper needle insertions. The 22-gauge 1.5- or 2-in. size is needed for the majority of regional techniques. A 5- or 6-in. 20-gauge needle is used for deep blocks, such as the celiac plexus, where free aspiration is desired.
Spinal Needles Spinal needles are necessarily longer (3.5 to 6 in.) and do not require a security bead when an introducer is used. They are usually styletted to prevent occluding the lumen with a plug of skin or subcutaneous tissue before the dura is punctured.
FIG. Regional Anesthesia Needles
Characteristic features of needles used for peripheral nerve blocks (top) include the “security bead” on the shaft just below its juncture with the clear hub and the shorter bevel angle compared to standard Quincke-type needle points (bottom). Further modifications include the prong for the attachment of a nerve stimulator electrode and the insulated shaft (middle). (Reprinted from P. G. Barash, B. F. Cullen, R. K. Stoelting (eds.), Clinical Anesthesia.
A number of bevel designs have been introduced since the original Quincke (sharp-bevel) style was first used, and most are designated by the name of their inventor. The rounded Greene and Whitacre points are designed to be less traumatic to the dura itself, apparently splitting or spreading rather than cutting the longitudinal fibers and thus promoting more rapid sealing of the dural hole. Experience with the rounded bevel design (especially the Whitacre and the Sprotte derivation of it) has shown an impressive reduction in the incidence of postdural puncture headache.The gauge of spinal needles is also important in terms of the probability of a headache, although it is apparently not as important as the needle type. Smaller needles create smaller holes and less transdural leak, but they are more difficult to insert and to aspirate. The 25-gauge needle is the size most frequently chosen as a reasonable compromise, and preferably with a rounded bevel.
Epidural Needles
Epidural needles are of a larger gauge, both to permit better assessment of loss of resistance and to allow the passage of catheters. An 18-gauge thin-walled needle is the smallest that will pass a 20-gauge catheter, and 16- or 17-gauge needles are commonly used for catheters.
FIG. Standard Regional Anesthesia Needle Bevels
A 19-gauge needle is satisfactory for single injections. A 22-gauge needle has been used, but the perception of resistance is more challenging through the narrower opening. A conventional Quincke-point needle can be used for a single-injection technique, although some practitioners prefer the blunter, short-beveled.
FIG. Wing Adapters on Needle Hub
The flanges attached to the hub of a standard epidural needle allow greater control of the advancement of the tip when the flanges are grasped between the thumb and forefinger while the other fingers rest on the skin and control the depth of insertion. These flanges come in several modifications.
Crawford needle for epidural or caudal insertion. The Tuohy needle with a curved point was first introduced to facilitate the passage of catheters, with a curved tip to encourage the catheter to advance in the direction of the spinal canal. Hustead modified this needle to reduce the bevel angle slightly in the hope of reducing the chance of shearing the catheter during passage The angle of both of these bevels may allow better direction of the catheter into the main axis of the epidural canal, but the greater curvature and the offset of the point of the needle from the midaxis of the shaft also make them more likely to deviate from the intended path during advancement. The longer bevel also creates the possibility that the tip of the needle may communicate a loss of resistance before the full opening of the bevel is completely through the ligamentum flavum. These needles may need to be advanced another 2 to 3 mm beyond their initial penetration of the ligament before a catheter will pass. Some of these needles are manufactured with 1-cm markings along the shaft to allow better appreciation of the needle depth or movement. Tuohy needles have also been manufactured with additional channels and end holes to facilitate simultaneous insertion of spinal needles for combined spinal-epidural anesthesia (CSE) The hubs of epidural needles also have been adapted in some cases with “wings” to allow better control of the depth of advancement, particularly in the thoracic region These additions are not usually needed for lumbar insertions.
Introducers Introducers are useful in spinal and epidural anesthesia. These are short, large-bore, sharp-pointed needles with a heavy hub to facilitate handling. For spinal anesthesia, these can be inserted through the skin and into the interspinous ligament. They create a rigid path to guide the more flexible small-gauge spinal needles. They offer the added advantage of allowing the tip of the spinal needle to bypass the skin and thus avoid contamination with prep solution or residual skin bacteria. For epidural use, a skin hole made with these needles reduces the resistance to insertion of the epidural needle and allows more sensitive appreciation of the ligaments themselves. Catheters. A multitude of catheters is available for insertion through epidural needles. The primary difference among them is the construction material, which gives different performance characteristics. The older polyvinylchloride (PVC) catheters are quite stiff. They resist kinking, but they are also associated with dural or venous puncture either on insertion or as a result of “migration” during patient movement after placement. At the other extreme, Teflon catheters are quite soft and flexible and rarely injure the dura, but they are prone to kink and occlude. Newer catheters of nylon, poly amide, or polyvinyl offer compromises between flexibility and rigidity (kinking and puncturing dura), and the appropriate balance is a matter of personal choice among the wide selection available. Stylets are available in the more flexible catheters to facilitate their introduction. These metal wires may be helpful in guiding the catheter in the needle shaft, but they should not be introduced beyond the needle tip,- if advanced into the epidural space, they may puncture the dura. Another feature offered in epidural catheters is the presence of lateral injection ports proximal to a closed, soft-tip end. This may reduce the chance of dural puncture, and the presence of multiple holes reduces the chance of occlusion of the catheter by tissue or blood clot blocking a single hole. However, multiple holes may also allow unrecognized dural or venous puncture, since a test dose may not give a reliable response if only one hole is in a vessel or into the dura. Many practitioners prefer a single-port catheter for this safety reason. Marks at 1- or 5-cm intervals along the first 20 cm are useful in guiding insertion of the catheter to the correct depth. Radiopaque markers on the catheter are useful in documenting position of chronic indwelling catheters or catheters for injection of neurolytic agents. The selection of any or all of these features is again a matter of personal experience and choice.
Adapters are needed to allow injection from a syringe into a catheter. These are usually of the Tuohy-Borst type, where screwing one fitting onto another tightens a rubber sleeve around the catheter and holds it in place. There are as many connectors available as there are catheters, and the selection is again a personal choice based on reliability and ease of use. All connectors should have a Luer-Lok adapter for fitting a syringe and a cap to provide sterility of the fitting between injections. All catheters used for repeated injections on sur- gical wards should be clearly labeled as epidural catheters to prevent unintentional injection of intravenous drugs.
Epidural catheters can also be inserted into the subarachnoid space, although the larger needles used for the standard catheters may increase the risk of headache. At one point, smaller micro-catheters (27 gauge or smaller) were employed through smaller needles to reduce this problem. Unfortunately, problems with neurotoxicity led to their withdrawal from the market.
Nerve stimulation
The peripheral nerve stimulator delivers a pulsed electric current to the tip of an exploring needle. As the needle approaches a nerve, depolarization is produced. Efferent motor nerves (A alpha fibers) are most easily depolarized, so these devices have the advantage of identifying mixed peripheral nerves by producing a muscle twitch rather than eliciting uncomfortable paresthesias. This also offers the anesthesiologist a method of confirming nerve localization in the obtunded or uncooperative patient. The degree of stimulation is dependent on the total current (amperage) and the distance between the current source and the nerve. This principle led to the development of nerve stimulators with variable outputs. A high current (around 2 mA) can be used to identify the approach to a nerve. A progressively lower current (0.5 to 1.0 mA) will document increasing proximity of needle to nerve. In practice, 2 mA will produce depolarization of a motor nerve at a distance of about 1 cm. As the needle is moved closer to the nerve, a smaller current (less than 1 mA) will be able to elicit a response. Stimulation with 0.5 to 1.0 mA suggests adequate proximity. This is confirmed if 2 cc of local anesthetic injected at this point abolishes the twitch response. Nerve stimulators designed for monitoring neuromuscular blockade have been used for nerve localization, but they are not ideal. The ideal nerve stimulator should have a variable linear output with a clear display of current delivered. The amount of current required is less (approximately one-third) if the exploring needle is used as the negative (cathode) lead and this lead (usually black) should be clearly identified as the one for attachment to the needle. The connection is usually done with an “alligators-type clamp. Ideally, the connector is also sterile, but an unsterile lead may have to be attached by an assistant after the needle is in place near the nerve. Adequate connections require a metal needle hub or adapter between the syringe and a plastic-hub needle. A length of plastic tubing may intervene between the metal connector and the actual needle point; the local anesthetic solution itself will serve as a conductor to the needle point. There are several commercial sheathed needles with electrical connectors incorporated in their design, and all work well.
FIG. Nerve Stimulator Attached to Regional Block Needle
The negative (black) lead is attached to the exploring needle, while the positive (red) is connected to a reference electrocardiogram (ECG) pad used as a “ground.” The stimulator is set to deliver 1 to 2 mA of current to detect the nerve. The current is reduced further as the needle approaches the nerve. 0.5 mA will produce motor stimulation when the needle is adjacent to the nerve.
The other lead (anode, reference, red) should be attached to an ECG pad over the shoulder or buttocks, arranged in a pattern so that the current does not directly traverse a peripheral nerve path or flow through the myocardium. Electrically insulated (sheathed, Teflon-coated) needles concentrate more current at the needle tip and will increase the accuracy of nerve localization. The electrical isolation of the needle shaft causes the depolarization to decrease after the needle point passes the nerve, which is not the case with unsheathed needles. Sheathed needles are more expensive, but the greater accuracy may make the expense worthwhile. Nerve stimulators are not a substitute for a knowledge of anatomy and proper initial needle placement. They will only help document the proximity of the needle to the nerve once it is already near. The stimulator cannot find the nerve for the novice who has not reviewed anatomy. Use of a nerve stimulator will not increase the rate of success. Although it is speculated that their use may reduce the potential for nerve damage, no study has shown an increased safety margin wheerve stimulators are used. Stimulators are particularly useful in the obtunded or uncooperative patient, though, in whom motor stimulation may be a needed substitute for identification of a paresthesia. Stimulators are also useful for teaching residents in a heavily premedicated patient, and they are particularly useful in pediatric practice, where blocks are usually performed on a sedated or anesthetized patient. One problem is that the use of a stimulator usually requires two individuals—one sterilely gloved for the procedure and the other operating the device.
SURGICAL SUTURE
The choice of material for a surgical suture or ligature is, within reasonable limits, less important than the technique employed. The suture must be properly placed and securely tied with appropriate tension to fulfill its purpose. Although any of several types of sutures may be satisfactory in a specific situation, one may be more advantageous than another, and some knowledge of the characteristics of a suture will influence proper selection. The composition of the material, strength, knot efficiency, tissue response, and other factors are important. A number of these factors must be considered for an ideal suture (see “Characteristics of Ideal Surgical Suture”). Some of these are obviously mutually exclusive but help form a basis for suture selection. The variety of sutures, discussed below, that are now available indicates the developments in this field in the past few years.
HISTORY
The original use of sutures and ligatures is obscure, but ancient Greek and Egyptian medical writings describe such materials as linen, cotton, leather, animal tendon, catgut, and metal wire. Rhoads and his associates reviewed in detail the use of catgut.
CHARACTERISTICS OF IDEAL SURGICAL SUTURE
May be used in any operation
Handles comfortably
Adequate tensile strength
Tissue reaction minimal
Not conducive to infection
Knots securely
Does not fray
No shrinkage or excessive extension
Nonelectrolytic, noncapillary, nonallergenic,
noncarcinogenic Sterilized without alteration Absorbed after purpose served Inexpensive
In 1816, Philip Syng Physick published the results of his experiments and receives credit for the general use of catgut. Lister in 1868 described the first of his many experiments with catgut. Mace wen in 1881 first recommended chromi-cizing catgut to increase the strength. Over the years numerous studies of absorption and changes in strength in implanted catgut were reported, notably those of Howes and of Jenkins and their associates. The work of Meleney and Chatfield eventually assured sterility of the catgut. Halsted, after observing the use of silk by Kocher, utilized this material for years before his definitive description of the silk technique in 1913. Whipple in 1933, as well as others, confirmed the superiority of silk in clean wounds. Meade and Ochsner in 1940 described their experimental and clinical results with cotton; Babcock in 1947 recorded his extensive experience with stainless-steel wire.
Nichols and Diak in 1940 first compared nylon with other suture material and concluded that the synthetic suture is satisfactory for clinical use.9 Since then a number of synthetic sutures, described later, have been offered by suture manufacturers and have been used extensively.
ABSORBABLE SUTURES
CATGUT Catgut in either plain or chromicized form is initially uniform in finish and strength. It handles well, knots securely when properly tied, and, because it is absorbed, may be indicated when a wound may be contaminated. The disadvantages are the erratic behavior in loss of strength, absorption, and tissue reaction. In situations such as fascial closure, the rate of loss of breaking strength is unpredictable.
Implantation studies in animals show that breaking strength may be retained near the initial level for 2 to 3 weeks in some, whereas in others, a decided loss of strength occurs during this period. Absorption is equally erratic; remnants of the catgut may persist for months. Early after implantation in tissues, catgut acts as any other monofilament suture (the tissue reaction to all sutures for 5 to 7 days is secondary to the trauma of passage of the needle and insertion of the suture). The perisu-tural tissue reaction occurs when absorption of the catgut begins A mononuclear cell infiltrate first develops about the suture, then about the fragments of suture as absorption progresses. Polymorphonuclear leukocytes are seldom an important component, although occasionally eosinophils may be. After absorption is complete a collection of mononuclear cells with foamy brownish cytoplasm remains for a variable period.
SYNTHETIC ABSORBABLE SUTURE Two types of absorbable sutures are available: polyglycolic acid, a homopolymer of gly-colic acid, and polyglactin, a copolymer made from lactide and glycolide. They are made by melt extrusion under controlled temperature and pressure, both are multifilament, and their characteristics are so similar that they may be considered together. Both feel slightly rough but handle well and knot securely. Their initial tensile strength is greater than that of silk or catgut but less than that of Dacron. After implantation in tissue the loss of strength is predictably linear to a zero point in about 21 to 25 days. The absorption is equally predictable, beginning in the fourth week and being complete in the fourth month. The tissue reaction is unique. After the initial reaction has subsided, perisutural cellular reaction of any type rarely develops.
Figure (A) An intense cellular reaction develops as catgut is absorbed. (B) Synthetic absorbable suture shows cellular invasion about the fibers but no reaction around the suture. (C) Site of wire suture with fibrous tissue cuff and minimal reaction. (D) Compact silk suture with modest cellular response.
The interstices of the suture are invaded by mononuclear cells, with some lymphocytes and occasionally giant cells. As absorption takes place the suture fibers become smaller, although not uniformly, and then disappear. The cells that have invaded gradually decrease iumber at the same time. In addition to the two materials described previously, more recently a third synthetic absorbable suture has become available. This is a polymer, polydioxanone (PDS), which is monofilament and uniquely flexible. Young’s modulus is about a fourth that of polyglycolic acid or polyglactin; the initial tensile strength exceeds that of polypropylene and nylon. Absorption is by hydrolysis with minimal tissue reaction, beginning about the 90th day and being complete in 180 days. Most important, the implantation studies of Ray and colleagues17 show the loss of breaking strength to be almost linear to zero in 8 to 10 weeks. After 4 weeks, 71% of the initial strength of size 2-0 remained and 46% of size 6-0. From the clinical standpoint the advantages of the synthetic absorbable sutures over catgut are apparent: adequate initial tensile strength, a predictable rate of loss of strength and of absorption, and minimal tissue reaction. Although catgut may be indicated in specific situations the synthetic absorbable sutures should generally replace catgut.
NONABSORBABLE SUTURES
SILK Silk is generally considered the standard nonabsorbable suture, more from tradition than from fact, as silk may be absorbed. In some patients, however, silk will persist unchanged (microscopically) for at least 20 years. Silk is a protein with a core of fibroin analogous to horn, hair, and similar dermal products, according to Meade and Ochsner. It is a dyed, waxed, multifilament suture with an initial tensile strength greater than cotton but less than the synthetic nonabsorbable materials. The wide usage of silk is at least in part due to the surgeons trained by Halsted and their subsequent generations of trainees. Silk handles most comfortably, because of its pliability, and knots satisfactorily. The strength of silk is dependable to the range of 6 to 8 weeks. After this, wide variation is found. In animal implantation studies extending through 5 years, an occasional strand of silk was found that had retained appreciable strength. Absorption is equally variable, as noted earlier.
Histologically, three patterns of reaction to silk are found. Usually the silk remains as a compact bundle surrounded by a connective tissue zone of variable thickness. Within this and nearest the suture, two or more layers of mononuclear cells, mainly histiocytes, persist for years. In the second pattern the interstices are invaded by fibroblasts, histiocytes, and lymphocytes. Giant cells may be present. Least often, and usually about a knot, a granulomatous reaction is seen with or without fragmentation of the silk. To define precisely the current indications for silk as sutures and ligatures is not feasible. The synthetic materials, both absorbable and nonabsorbable, have replaced silk in many operations.
COTTON For use as sutures and ligatures, the properties of silk and cotton are so similar that detailed description is unnecessary. The handling, knot stability, changes in strength, and tissue reaction do not differ greatly. One decided advantage of cotton is that it is the most inexpensive of the sutures.
WIRE Stainless-steel wire has a high tensile strength that is not altered by implantation in tissue. The surface allows smooth gliding through tissue, and the knot holds firmly. Wire is stiff and the ends sharp, which causes problems in its use until the surgeon becomes accustomed to it. Multifilament wire is more easily handled. Wire used for such purposes as abdominal closure may be seen to have broken in x-ray films made later. If the cut ends of the wire are not turned in they may erode to or through the skin in a thin patient. A major advantage of wire, other than strength, is that it does not tend to support infection. The tissue reaction to wire is modest, the area about the wire showing a variable concentration of mononuclear cells and a small amount of fibrous tissue. Monofilament wire may have a slight tendency to cut into enclosed tissues. After technical proficiency has been attained in using wire, it provides a versatile suture for a number of uses.
NYLON Nylon is a polyamide that had most extensive use as a monofilament but in recent years has become available in a multifilament form that handles much like silk. The monofilament is somewhat stiff, and a secure knot can be obtained only with multiple loops. The initial tensile strength is excellent and in tissues decreases slowly over a period of years. In our animal implantation studies, monofilament nylon has most consistently stimulated the least tissue reaction of any material examined. The usual finding is a narrow, nearly acellular type of fibrous tissue The multifilament suture is prone to incite more reaction, similar to Dacron, as noted later. Nylon is another suture material with a wide range of applications. Extremely fine nylon is used in microsurgery. Small-caliber nylon as a continuous suture provides precise skin closure. Heavy nylon may be useful for difficult abdominal closure.
DACRON Dacron has gained extensive application because of sustained strength, low tissue reactivity, and good handling properties. It is a multi-
Figure.(A) Dacron suture stimulates little cellular reaction. (B) Teflon shed from coated Dacron suture is seen as granular appearing material. Cellular reaction to both nylon (C) and polypropylene (D) sutures is essentially absent.
filament suture and may be obtained uncoated or coated with such materials as Teflon, silicone, or polybutylate. The coated sutures hold a knot less well than the uncoated and require additional loops in the knot, the number varying with the specific suture. The initial tensile strength is high and is maintained in tissues. Dacron stimulates a very moderate tissue reaction, much less than silk or cotton but more thaylon. The fibers tend to remain compact, surrounded by a connective tissue zone invariably containing a number of mononuclear cells near the suture. Occasionally fibrous tissue invades the interstices of the suture. The Teflon-coated sutures, for an unknown time extending from months to years, appear to shed the Teflon into the adjacent tissues. These fragments in turn stimulate a secondary mononuclear cell reaction. After the Teflon has disappeared the reaction is similar to that of uncoated Dacron. We have not investigated the other two coatings, but from previous experiments with sili-cone-treated silk, we would not anticipate the reaction to differ from that of uncoated Dacron. Dacron, either uncoated or coated, is useful in essentially any application in which silk has been employed, in addition to some operations in which silk is now known to be contra-indicated, namely, synthetic grafting to vessel anastomoses. Teflon shed from the suture should cause no problems except in the most delicate operations such as nerve or tendon suture.
POLYPROPYLENE A polyolefin, polypropylene is provided as a monofilament suture of excellent, maintained strength with a major advantage of sliding through tissues very easily. As a monofilament synthetic material with a memory, and relatively low coefficient of friction, knot security is obtainable only with multiple loops. The very minor tissue reaction stimulated by polypropylene is the same as that by nylon. Infrequently, however, fibrillation of the polypropylene occurs, and each fragment then causes a reaction about it. The most extensive use of polypropylene sutures has been in cardiac and vascular operations; in minor surgery its application has been more limited.
HEALING OF SKIN
Since an important component of minor surgery relates to healing of the skin, a brief discussion seems appropriate. The following is based mainly on the excellent studies of Ord-man and Gillman. Their investigations were carried out on pigs, whose skin closely resembles that of humans. They emphasized that a healing cutaneous wound is not a thin line but a vertically placed block of new tissue extending down into the subcutaneous fat for the entire depth of the incision.
Blood and serum rapidly form a linear scab over the wound after closure, and the epithelium grows beneath this. Within a few hours of injury, epithelium on either side of the incision thickens and begins to migrate across the deficit as two long sheets. The gap is bridged in 24 to 48 hours. The new epithelium then thickens, and some downward growth extends into the dermal breach. The epithelium then acquires some of the structural features of the uninjured epidermis, and about the fifth day, keratin forms with resultant loosening of the overlying scab. In the dermis, vertically oriented strands of fibrin enmesh erythrocytes and white cells, mainly polymorphonuclear. Phagocytosis begins about the second day, and the cellular exudate changes to a primarily mononuclear one. Fibroblasts, also vertically oriented, are present about the fourth day with the first appearance of collagen 24 hours later. After the seventh day, the collagen lies across the incision to interdigitate with adjacent normal tissue or nearby transected preexisting collagen bundles. After the 21st day the cellular and vascular elements decrease gradually, and the scar usually widens, even with sutures in place. The collagen then thickens and forms bundles, and the junction between old and new tissue becomes more difficult to define. Depending on the body area involved, a variable number of skin appendages are divided. Throughout the incision, epithelial growth may occur from each divided end of, for example, a hair follicle. The epithelial aggregation may be solid or cystic but is absorbed after several weeks. The major emphasis of Ordman and Gillman was the advantage of microporous adhesive tape over sutures for skin closure, and for this reason, they provided detailed descriptions of the reaction about the suture as it traverses the skin. Briefly, the suture stimulates an inflammatory reaction along its track. A granulomatous, then fibrous, tissue response develops. In addition, from each point of penetration of the skin, epidermis grows along the suture, first on the convex side but eventually as a tube surrounding the suture. Keratin is formed between the fifth and tenth day, and even in the absence of infection the inflammatory response is manifested grossly by a reddish halo about the points of entry and exit of the suture. After the suture is removed the reaction subsides and the epithelium is eventually absorbed.
METHODS OF SUTURING
The variety of incisional, excisional, and traumatic wounds, as well as the various tissues that may be involved in minor surgery, make a detailed description of all applicable suture techniques too extensive to be discussed here. Therefore, assuming that the deeper structures have been approximated appropriately, emphasis will be given to skin closure. Suture closure of the skin is usually interrupted or continuous, simple or mattress in type. Other methods have been described, but these generally are most satisfactory. The beginner is well advised to learn first the proper use of the interrupted mattress suture. The spacing and amount of tissue within the suture loop are dependent to a degree on the site being closed. However, an effort is made to encompass the same amount of tissue on each side of the wound, as well as to maintain the same angle of insertion and egress. A straight or curved cutting needle with material such as nylon or silk swedged on is used. The first insertion is sufficiently deep to approximate the skin and relieve any tension; the return insertion is in the most superficial layer of the epidermis, encompassing only enough tissue to allow approximation. As the knot is formed the tension applied to the suture loop must be precise: Excessive tension results in cutting of the suture and increased tissue necrosis, whereas insufficient tension does not appose the wound surface. The same principle applies when a cor inuous suture is used. The surgeon should keep in mind that some swelling of the tissues occurs after closure, which increases the possibility of the skin suture cutting into the epidermis and leaving the characteristic ladder pattern. Although the surgeon and patient hope for a minimal scar in any situation, in some areas, such as the face, this is more important than in others. Accordingly, tension is relieved by subcutaneous sutures with the knots deep, and the skin is approximated with very fine suture material, meticulously placed and tied. A continuous subcuticular suture provides good apposition while avoiding the necessity for suture removal and the possibility of suture scars. Although the use of nonabsorbable material, usually as a pullout suture, has been described, a fine synthetic absorbable suture is preferable. The knots can be buried, and the suture linearly placed in the inner aspect of the dermis to provide good apposition of the epidermis with slight eversion. The time for removal of skin sutures depends on a number of factors, one being the tensile strength of the skin. Through the fourth day the tensile strength is slight as it is dependent on the adherence of the fibrin in the dermis and the strength of the epithelial bridge. The tensile strength increases rapidly from the fifth through the fifteenth day, then increases more slowly. Theoretically, sutures would be removed about this time, but their prolonged presence in tissue has adverse effects. Granulation and epithelialization of the suture track, noted earlier, will develop; the presence of a foreign body increases the chances of infection; the puncture wounds of entry and exit are more likely to cause a visible scar. As a general rule, therefore, sutures should be removed between the sixth and tenth day, as recommended by Ordman and Gillman. Exceptions are obvious. For example, in the face half the sutures may be removed the second or third day (reinforcing if necessary with tape) and the remainder on the fourth or fifth day. In areas under tension such as those on the back or extremities, sutures may be left in for 10 to 14 days.
OTHER METHODS OF CLOSURE
The tissue adhesives (cyanoacrylates) have not fulfilled the early hopes for use except in a few specific locations and have little role in wound closure. Skin clips, which have long been available, have not been very satisfactory, but recently skin staplers have been developed. To increase rigidity the staple wire is larger than the usual wire suture. The staple is in the form of a wide inverted U, and as the staple is inserted the cross arm is bent, directing the legs of the staple into the skin. This elevates the enclosed skin and approximates the edges. A special instrument is needed for removal of the staples. The skin stapler provides rapid, satisfactory closure in many situations. Microporous surgical adhesive tape has not attained wide popularity, in spite of the strong recommendations of investigators such as Ordman and Gillman. Grabb and Smith have noted the advantages and disadvantages of tape. Tape saves time in application and removal, causes no skin reaction, avoids suture puncture scars, can be applied without an anesthetic, and can be left in place for long periods beneath dressings or casts. The disadvantages are the lack of eversion of skin edges, failure to adhere to wet skin, and the possibility of its coming off during bathing and of its premature removal by children or uncooperative patients.
Topographical anatomy of fronto-parieto-occipital region
SCALP PROPER
The scalp is made up of the soft parts which cover the skull from one temporal line to the other and from the eyebrows in front to the superior nuchal lines behind. It is of
particular interest to the surgeon because injuries and infections in this region may involve the skull, the sinuses, the meninges or the brain, and superficial cysts and vascular tumors may be found between its layers. It consists of 5 layers. If one spells the word
“SCALP,” these layers can be remembered
S—Skin
C—Connective tissue (dense)
A—Aponeurosis (occipitofrontalis)
L—Loose connective tissue
P—Periosteum (pericranium)
SKIN
The skin of the scalp is very thick and contains numerous hairs and sebaceous glands.
The hairs pass through it to an unusual depth, so that on reflecting the skin, the hair
roots are cut across and can be seen and felt on its deep surface. The sebaceous glands
may give rise to sebaceous cysts (wens). The skin is firmly attached to the underlying
dense connective tissue layer, and because of this it is removed with difficulty.
CONNECTIVE TISSUE
The dense connective tissue is the superficial fascia and acts as a firm bond of union
between the skin above and the aponeurosis below. In this dense, fibrous and unyielding layer run the superficial nerves and blood vessels of the scalp. This tissue holds the vessels firmly in place and prevents them from retracting; thus profuse bleeding results when the scalp is injured. Because of the great vascularity of the scalp it is rarely necessary to cut away any avulsed portions, as the flap usually retains its viability. Due to the compactness of the tissue, subcutaneous hemorrhage cannot spread extensively, and inflammation is associated with little swelling but much pain.
APONEUROSIS
The aponeurotic layer has been called the epicranial aponeurosis (occipitofrontalis
muscle or galea aponeurotica). It consists of two frontal and two occipital bellies, connected by the epicranial aponeurosis. The occipitalis arises from bone, but the frontalis has no bony origin. The occipital portion takes its origin from the outer half of the superior nuchal line; the frontalis arises from the skin and the subcutaneous tissues of the eyebrows and the root of the nose, where it blends with the orbicularis oculi. The muscles are continuous over the temporal fascia and have no well-defined lateral margins. The epicranial muscle belongs to the muscles of expression, since the posterior bellies draw the entire scalp backward and the anterior produce the characteristic transverse wrinkles in the skin of the forehead. The frontal bellies are supplied by the temporal branches of the facial nerve, and the occipital by the posterior auricular branches of the same nerve. The aponeurosis is felt as a dense and strong membrane which is connected to the frontalis in front and to the occipitalis behind, and on each side it passes superficial to the temporal fascia to become attached to the zygomatic arch. If a scalp wound gapes, the examining physician may
be certain that the galea has been divided transversely, since the skin is attached to
this structure so firmly that otherwise no gaping would be possible.
LOOSE CONNECTIVE TISSUE
The loose connective tissue has been referred to as the subepicranial connective tissue
space. It lies between the aponeurotic layer above and the pericranium below and
is really not a true space but a potential one. The important emissary veins connecting the venous sinuses in the skull with the veins of the scalp traverse this dangerous area. This loose areolar tissue permits free movements of the scalp and allows large collections of blood or pus to accumulate under the scalp without undue tension. The first three layers of the scalp can be easily separated from the pericranium through this space, and the knowledge of this plane permitted the Indians to become so clever at “scalping.” The space is closed posteriorly by the attachments to the superior nuchal line and laterally to the zygomatic arch; since the frontalis has no attachment to bones anteriorly, it is open in this direction. Due to this lack of attachment anteriorly, bleeding may occur into the loose connective tissue layer in head injuries; after a day or two of slow gravitation, the hemorrhage appears first in the upper eyelids and later in the lower.
PERIOSTEUM
The pericranium (periosteum) refers to the outer or external periosteum of the skull.It is loosely attached to the surface of the skull bones except at the suture lines and over the temporal fossae. At the suture lines it dips between the bones as a suture membrane which is blended with the periosteum of the interior of the skull, this latter being known as the outer layer of the dura. Collections of fluid beneath the pericranium can easily strip it but cannot pass beyond the suture line, and for this reason any swelling, such as cephalhematoma, will maintain the shape of the bone to which it is related. Surgeons do not hesitate to remove this layer, because the blood supply to the skull can be provided through the attachment of muscles.
VESSELS, NERVES AND LYMPH VESSELS
Arteries.
The vessels of the scalp are numerous and they anastomose freely. The arteries are derived from both the internal and the external carotids. Anteriorly, the supratrochlear and the supraorbital arteries ascend over the forehead, accompanied by the nerves of the same name. Both are branches of the ophthalmic artery (internal carotid). Their terminal branches anastomose with each other, with their fellows of the opposite side and with the superficial temporal (external carotid) of the same side. Laterally, the superficial temporal artery ascends in front of the ear (tragus), accompanied by the auriculotemporal nerve. It divides into anterior and posterior branches which supply large areas of scalp, and then it anastomoses with the corresponding vessels of the opposite side. Posteriorly, there are two arteries on each side, the posterior auricular and the occipital. The posterior auricular ascends behind the auricle and supplies that structure and adjoining parts of the scalp; the occipital extends over the occipital area accompanied by the greater occipital nerve. Since the arteries of the scalp anastomose so freely with each other and those of the opposite side, they form potential collaterals following ligation of the external or the common carotid artery on one side.
Veins.
The supratrochlear and the supraorbital veins unite to form the anterior facial vein (p. I l l ) , which makes an important communication with the superior ophthalmic. Nerves.
The nerves of the scalp are arranged in five groups which, considered from before backward, are: (1) The supratrochlear, appearing through the supratrochlear notch of the frontal bone and supplying the region of the glabella; (2) the supraorbital, which emerges through the supraorbital notch or foramen of the frontal bone, runs upward over the forehead and supplies the scalp as far as the crown of the head; (3) the auriculotemporal, which passes in front of the tragus of the ear and supplies the side of the scalp; (4) the posterior auricular, supplying a small area behind the ear; (5) the great occipital, which supplies the large area of skin over the occipital region and extends forward to the vertex. The lesser occipital nerve may or may not extend into the scalp. All the nerves of the scalp are sensory with the exception of the facial, which supplies the epicranius muscle. The supratrochlear, the supra-orbital and the auriculotemporal are branches of the trigeminal; the great auricular, the lesser and the great occipital are of spinal origin. Any of these may be affected by referred or neuralgic pains, the occipital and the supra-orbital being involved most commonly. Since the nerves of the scalp approach it from all directions and overlap, it is rarely possible to produce an adequate local anesthesia by a single nerve block. The area to be anesthetized must be ringed by a series of injec- tions. Like the vessels, the nerves travel in the subcutaneous tissue; hence, the solution must be placed in this layer and not in the subaponeurotic layer where it would spread with great ease but would not produce anesthesia.
Lymph Vessels.
The lymph vessels of the scalp and the face (Fig. 3) drain downward from the occipital region to the occipital glands, from the parietal and the temporal regions to the preauricular and the postauricular glands, and from the frontal region
to the submaxillary glands. Infected wounds, pediculi and furuncles usually cause the lymphadenitis associated with scalp pathology.
CIRSOID ANEURYSM
Reid and Andrus believe that cirsoid aneurysms are abnormal arteriovenous communi- cations. Ligation of the surrounding vessels improves the condition but rarely cures it; therefore, excision is the treatment of choice. Hemorrhage is the greatest danger.
Technic Short individual incisions are placed over the pulsating vessels leading to the aneurysm. These usually include the superficial temporal artery and vein, the occipital artery and vein, the supraorbital vessels and the frontal vein. These are ligated and divided. A continuous locked suture is placed around the mass to control bleeding. A U-shaped incision is made within the hemostatic suture, and a skin flap is reflected upward, thus exposing the aneurysm. The mass of vessels is carefully excised. The
encircling hemostatic suture is removed bit by bit, all bleeding points are controlled, and the skin flap is sutured into place.
Skull
EMBRYOLOGY The brain of the fetus is surrounded by a membranous capsule which is continuous with a similar capsule surrounding the spinal cord. Chondrification begins in the base, but ossification begins in the calvarium (supraorbital portion) before the chondrifying process has progressed very far. Bones which are formed in membrane are the frontal, parietal, squamous temporals, the greater wings of the sphenoid (except their roots) and the occipital above the nuchal lines. Centers appear for these bones about the 7th week. In general, the older basal portion of the skull is preformed in cartilage, but the facial and the roofing bones are formed intramembranously. At birth the skull reveals a lack of firmness between the bone sutures so that considerable movement can be produced, thus facilitating the “molding” which takes place during childbirth. The most striking feature of the neonatal skull is the marked disproportion between the cranium and the facial skeleton. At birth the facial region covers only one eighth of the skull as compared with one half in the adult.
FONTANELLES
The fontanelles) are unossified spaces which appear at the angles of the parietal bones. The anterior fontanelle is 4-sided and is bounded by the margins of the 2 frontal and the 2 parietal bones. Intracranial pulsations may be transmitted through this tissue and are usually visible in infants. Extension of the bony margins closes this
fontanelle before the age of 2 years. The posterior fontanelle is 3-sided and is bounded by the occipital and the 2 parietal bones; its sides pass laterally into the lambdoid sutures and its apex to the sagittal suture. It is usually closed during the first year of life. These membranous areas exist in the midline of the cranium and are of great value in determining the position of the fetal head during labor. Fontanelles are also present at the pterion and the asterion. The suture between the 2 frontal bones of the newborn child disappears around the 3rd year of life but may persist indefinitely, giving rise to a metopic suture.
SKULL PROPER
The word “skull” refers to the entire skeleton of the head and the face, including the mandible. “Cranium” refers to the skull minus the mandible. “Calvarium” refers to the skull after the bones of the face have been removed (that portion which is above the supra-orbital ridges). The skull as a whole is slightly flattened from side to side. When viewed from above it appears to be smooth, but from below it is very uneven. It is oval in shape, wider behind than in front, and is composed of flattened or irregular bones that are joined together immovably, with the exception of the mandible. The skull is made up of 24 bones, including the mandible and the bones of the head and the face. The bones consist of 2 tables or plates of compact substance which enclose a layer of spongy bone between them known as the diploe’. The diploe’ contains marrow and is supplied by numerous small diploic branches that arise from the arteries of the scalp and the dura mater. The veins of the diploe anastomose with each other to form the main diploic veins. In some of the bones the diploe is absorbed, leaving cavities which are referred to as air sinuses and are situated between the tables of compact bone. The sinuses communicate with the cavity of the nose and have a mucous lining that is also continuous with the nasal cavity. The exterior of the skull should be viewed from 5 different positions, each of which is referred to as “norma”: norma verticalis (from above); norma basalis (from below); norma frontalis (from in front); norma occipitalis (from behind); norma lateralis (from the side).
NORMA VERTICALIS
The top of the skull shows portions of 4 bones: the frontal, the occipital, the right and the left parietals. They are united by serrated bony seams called sutures, which have interlocking jagged sawlike edges. The suture that unites the frontal Skull Proper 7 to the 2 parietal bones runs across the skull from side to side in a crownlike arrangement and is known as the coronal suture. That suture which unites the occipital to the 2 parietal bones resembles the Greek capital letter lambda which looks like an inverted “V” and is known as the lambdoid suture. “Sagitta” means arrow, and the lambdoid suture and the sagittal suture, with the anterior fontanelle, have a definite resemblance to an arrow. The meeting point between the coronal and the sagittal sutures is called the bregma. At birth the parts of the frontal and the parietal bones around the bregma are not fully ossified; because of this a lozengeshaped membranous area results which is called the anterior fontanelle.
FIG. The fetal skull: (A) Lateral view, showing average measurements. (B) Oblique view, showing the sutures and the fontanelles.
This yields to the touch, and the pulse rate can be counted here. That point at which the sagittal and the lambdoid sutures meet is called the lambda and marks the site of the posterior fontanelle. The vertex, the highest point of the skull, is on the sagittal suture near its middle. The parietal foramen is a small opening present on either side of the sagittal suture; it is usually big enough to admit a pin, and a small artery and vein pass through it. This vein connects the veins of the scalp with the superior sagittal sinus; hence, an infection from the scalp may travel along this vein and involve the sinus. It is interesting to note that the sagittal suture is less serrated between the two parietal foramina.
NORMA BASALIS
This view is obtained when the skull is turned upside down, thus exposing the external surface of its base. The anterior part of this aspect is occupied by the bony palate, which is formed by the palatine processes of the maxillae and the horizontal plates of the palatine bones. In the median plane anteriorly, the incisive fossa receives the openings of the lateral incisive canals, which transmit the terminal parts of the greater palatine vessels to the nose and the descending terminal branches of the long sphenopalatine nerves. Anterior and posterior median incisive canals are sometimes present. The greater palatine fossa, which transmits the greater palatine vessels and nerves, is found in the posterolateral corner near the last molar. The lesser palatine fossae lie immediately behind the greater. Behind and above the hard palate are the choanae (the posterior bony apertures of the nose). These are separated from each other by the vomer and are bounded laterally by the medial pterygoid plate. The pterygoid plates are a pair of large lateral and medial processes projecting downward from the roots of the greater wings of the sphenoid bones. Between these processes is an interval known as the pterygoid fossa, which opens posteriorly and is about half an inch in width. The free border of the medial plate ends below in a hook called the hamulus. This gives attachment at its tip to the pterygomandibular ligament, and by its posterior border to the upper fibers of the superior constrictor muscle of the pharynx. The tensor palati tendon twists around its lateral and anterior aspects. The lateral plate gives origin to the lateral pterygoid muscle on its lateral surface and to the medial pterygoid on its medial surface. Lateral to the structures just described is the roof of the infratemporal fossa. Posterolateral to the plates, the foramen ovale is found, which is quite large and transmits the mandibular nerve, the accessory meningeal artery and some small veins that connect the cavernous venous sinus with the pterygoid venous plexus. Some lymph vessels from the meninges also pass through this foramen, as does the lesser superficial petrosal nerve at times. Posterolateral to the foramen ovale is the foramen spinosum, which transmits the middle meningeal vessels. The zygomatic arch is a prominent feature of this aspect. At its caudal end is found the articular fossa, which receives the articular process of the mandible. The foramen lacerum is a large and jagged aperture located at the base of the medial pterygoid plate. The carotid canal, which is posterolateral to the foramen lacerum, is a tunnel in the petrous portion of the temporal bone through which the internal carotid artery travels on its way to the cranial cavity. From its opening the canal leads upward for a short distance, bends to become horizontal and runs in a medial direction and forward to open into the foramen lacerum. The canal is in immediate relationship to the middle and the internal ears. The thumping sounds that one hears in the head during moments
FIG The top of the skull, viewed from above (norma verticalis).
of excitement or after violent exertion are due to the beating of the internal carotid artery against the bone that separates it from the internal ear.The jugular foramen is a large opening with uneven margins situated directly behind the carotid canal. The largest structure in this foramen is the internal jugular vein. Other structures associated with it will be reviewed when the interior of the base of the skull is discussed. The jugular foramen is opposite the external auditory meatus, and that part of the bone which bounds the foramen forms the floor of the middle ear. It is important to keep this relationship in mind since, in diseases of the middle ear, infection may pass through the bone and attack the internal jugular vein. Directly lateral to the foramen is the styloid process. Two ligaments (the stylohyoid and the stylomandibular) and 3 muscles (the styloglossus, the stylohyoid and the stylopharyngeus) are attached to this process. The stylohyoid ligament runs from its tip to the hyoid bone, and the stylomandibular ligament extends from the front of it to the posterior border of the mandible. The stylomandibular ligament is a thickened part of the fascia that covers the anteromedial aspect of the parotid gland. The stylo-mastoid foramen is found immediately at the base of the styloid process and is the
FIG The external surface of the base of the skull (norma basalis).
foramen that transmits the facial nerve from the brain to the exterior of the skull. The stylomastoid branches of the posterior auricular vessels are also transmitted by this foramen. The mastoid process can be palpated under cover of the lobule of the auricle but is not recognizable as a bony structure until the end of the 2nd year. The mastoid foramen, which is variable in size and position, is found posterior to the mastoid process. It transmits a vein to the transverse sinus and a small branch of the occipital artery to the dura mater. The foramen magnum, the largest bony foramen in the skull, is the opening through which the medulla oblongata, or lowest subdivision of the brain, becomes continuous with the spinal cord. Its level is approximately the same as that of the mastoid process on the side of the head, and it is opposite a point on the back of the neck midway between the external occipital protuberance and the spine of the second cervical vertebra. The occipital condyles are the large, smooth and rather oblong protuberances that lie at the margins of the foramen magnum. They articulate with the atlas, and nodding movements of the head take place at the joints between the atlas and the condyles.
FIG. X-ray study of the front of the skull (posteroanterior projection): (1) parietal bone, (2) coronal suture, (3) frontal sinuses, (4) crista galli, (5) sphenoid bone and sinus, (6) zygoma, (7) lesser wing of sphenoid bone.
The anterior condylar canal is above the lateral margin of the anterior part of the condyle. It is usually hidden by the condyle, and the skull must be tilted before the opening can be seen. The anterior condylar canal is smaller than the jugular foramen and is the opening that transmits the hypoglossal nerve. The posterior condylar canal, when present, passes above the posterior part of the condyle and opens into the posterior fossa. It transmits an emissary vein that connects the sigmoid venous sinus with the suboccipital venous plexus. Behind the foramen magnum a bony crest is noted, known as the external occipital crest, which ends in an elevation called the external occipital protuberance (inion). From the region of the midpoint on this crest the inferior nuchal line curves laterally on each side, but the line is often poorly defined and difficult to see. The superior nuchal line curves laterally on each side from the external occipital protuberance and separates the scalp area above from the area for the neck muscles (nuchal area) below.
NORMA FRONTALIS
The front of the skull, uneven in contour, is made up of 6 regions: (1) frontal (forehead); (2) orbital; (3) nasal; (4) zygomatic; (5) maxillary (upper jaw); (6) mandibular (lower jaw).
Frontal Region. The forehead, or frontal region, is formed by the frontal bone. Superiorly, it merges into the top of the skull; inferiorly, it is limited by the orbits and the root of the nose. The depression at the nasal root is called the nasion; it is found at the point in the median plane where the 2 nasal bones articulate with the frontal bone, and is opposite the anterior extremity of the brain. Directly above the orbital margins are 2 elevations, the superciliary arches. These give prominence to the eyebrows and are more elevated in the male. The elevation that exists between the superciliary arches (between the eyebrows) is called the glabella, so designated because the overlying skin is bald or glabrous. Behind the superciliary arch and in the anterior part of the frontal bone a large air space is usually found; it is known as the frontal sinus. The frontal eminence is the most convex part of each frontal bone and is situated about 2 fingerbreadths above the lateral end of the superciliary arch. The supra-orbital foramen or notch is located immediately above the upper border of the orbital opening at the junction of its medial with its lateral two thirds. It transmits the nerve and the vessels of the same name. The supra-orbital margin ends laterally in a prominent projection called the zygomatic process of the frontal bone; it articulates with the zygomatic bone. The zygomatic process is easily felt at the lateral end of the eyebrows and may be a serviceable landmark, since it marks a line that curves upward and backward from it and is known as the anterior part of the temporal line. In thin people this line can be both felt and seen.
Orbital Region. Each orbit is a deep cavity which resembles an irregular cone and may be likened to a pyramid having 4 walls, an apex and a base. The bones that form
the orbital pyramid are the maxillary, zygomatic, sphenoid, frontal, palatine, ethmoid and lacrimal. The medial walls are parallel and separated by the nasal cavity; the lateral are at right angles to each other. The apex of the pyramid is marked by the optic foramen. Probes passed through these foramina meet at right angles near the dorsum sellae. The base of the pyramid is the opening on the face and the boundaries are the margins of the orbit. The roof, or superior wall, of the orbit is concave and is formed mainly by the orbital plate of the frontal bone and posteriorly by the lesser wing of the sphenoid. It separates the orbit from the sinus anteromedially and from the anterior cranial fossa elsewhere. The lacrimal gland occupies a fossa in the anterolateral part of the roof. At the medial angle the trochlea is attached. This is a small fibrocartilaginous ring through which the tendon of the superior oblique muscle passes. The point of attachment is usually marked by a small pit or spicule of bone called the trochlear fossa or spine. The floor, or inferior wall, is formed by the orbital plate of the maxilla. This plate also forms the roof of the subjacent maxillary sinus. A great part of the floor is separated from the lateral wall posteriorly by the inferior orbital fissure. The anterior end of this fissure is closed, but the posterior meets the medial end of the superior orbital fissure at the apex of the orbit. The inferior fissure transmits the maxillary nerve (which becomes the infra-orbital nerve), the infraorbital vessels, the zygomatic nerve, nervous twigs from the sphenopalatine ganglion to the lacrimal gland, the periosteum of the orbit, and a vein connecting the ophthalmic veins with the pterygoid venous plexus in the infratemporal fossa. The infra-orbital groove leads forward on the floor for a short distance from the fissure and then tunnels through the floor to reach the infra-orbital foramen, which transmits the nerve and the vessels of the same name. The lateral wall is formed by the orbital process of the zygomatic bone and the orbital surface of the great wing of the sphenoid. Between the lateral wall and the roof, near the apex of the orbit, the superior orbital fissure is found. Through this fissure the oculomotor, the trochlear, the ophthalmic division of the trigeminal and the abducens nerves enter the orbital cavity, accompanied by orbital branches of the middle meningeal artery. Passing backward through this fissure are the ophthalmic veins and the recurrent branch of the lacrimal artery which reach the dura mater. The superior orbital fissure separates the lateral orbital wall from the roof, and the inferior fissure separates this wall from the floor. Of the 4 walls, the lateral is the thickest and the only one that is not in close contact with the paranasal sinuses; resection of this wall gives safe access to the contents of the orbital cavity. The medial wall is very frail and is formed, from before backward, by the frontal process of the maxilla, the lacrimal bone, the lamina papyracea of the ethmoid and a small part of the body of the sphenoid in front of the optic foramen. This wall contains the lacrimal fossa, which lodges the lactimal sac, the anterior ethmoidal foramen, which transmits the nasociliary nerve and the anterior ethmoidal vessels, and the posterior ethmoidal foramen, which accommodates the posterior ethmoidal nerve and vessels. The medial wall is in close contact with the sphenoid sinus posteriorly and the ethmoid sinuses anteriorly, these sinuses separating the orbit from the cavity of the nose. The apex, which is situated at the back of the orbit, corresponds to the optic foramen. This short cylindrical canal transmits the optic nerve and the ophthalmic artery. The ophthalmic vein passes through the superior orbital fissure; hence, it does not travel with its artery. Injury or infection in the orbital cavity may travel in the following ways: superiorly, to the frontal sinus or the anterior cranial fossa, which contains the frontal lobe of the brain; inferiorly, to the maxillary sinus; medially, near the apex, to the sphenoid sinus; farther forward to the ethmoid sinuses, which separate the orbit from the cavity of the nose, and within the orbital margins to the floor of the fossa for the lacrimal sac; laterally, through the posterior part of the orbit to the middle cranial fossa, which lodges the temporal lobe of the brain, and more anteriorly to the anterior part of the temporal fossa.
Nasal Region. The bony part of the external nose is best seen from the norma frontalis. The nasal cavity itself is discussed elsewhere (p. 83). The osseous part of the nose is formed by the 2 nasal bones in the bridge of the nose and on each side by the frontal process of the maxilla, which lies behind the nasal bone. This part of the maxilla also forms the medial margin of the orbital opening. The nasal cavity is divided by a thin median partition or septum into right and left halves. The principal part of the septum seen through the anterior bony aperture is the perpendicular plate of the ethmoid that forms the upper part; it is usually bent to one side or the other. The side walls of the nasal cavity are uneven because of 3 rough, curled, bony plates called conchae, which project downward from each side wall. That portion of the cavity that lies below and lateral to each concha is called a meatus of the nose (superior, middle and inferior). The superior concha is too far back to be seen through the anterior aperture, but the middle and the inferior conchae and meatuses are visible. Zygomatic and Maxillary Regions. These form the cheek bones and the upper jaw regions, respectively. The upper jaw region is situated between the orbits and the teeth. The anterior nasal spine is a sharp spur of bone which projects forward from the 2 maxillae at the lower margin of the anterior aperture of the nose. The maxilla ends inferiorly in the alveolar border, which has slight ridges marking the roots of the anterior teeth, the most prominent of which are the canines. The canine tooth is the third, counting from the middle in front. Near the lower margin of the orbit and almost immediately above the canine fossa is the infra-orbital foramen, which transmits the infra-orbital vessels and nerve and is located about one fingerbreadth lateral to the side of the nose. The zygomaticofacial foramen appears as a small opening on the zygomatic bone immediately below the lateral part of the lower margin of the orbit. It transmits the zygomaticofacial branch of the zygomatic nerve and a small branch of the lacrimal artery. The large single air space found inside the maxilla is called the maxillary sinus (antrum of Highmore); it communicates with the nasal cavity.
Mandibular Region. The mandible is the largest and strongest bone of the face and it contains the lower teeth. The bone develops in 2 symmetrical halves, which fuse early and ossify during the first year. It consists of a horseshoe-shaped body and a pair of flat, broad rami that stand up from the posterior part of the body. Two processes project upward from the upper border of each ramus: an anterior called the coronoid process, and a posterior designated as the condyloid process, which is divided into a head and a neck. The external surface of the body of the bone is marked in the median line by a faint ridge, the symphysis mend, or line of junction of the 2 embryologic pieces of bone. The ridge divides below and encloses a triangular eminence known as the mental protuberance. the base of which is depressed in the center but raised on either side to form the mental tubercles. In the region of the protuberance the bone is bent forward to form the chin. The alveolar is the upper border, so called because it is occupied by a row of pits or alveoli, 16 iumber, which form the sockets for teeth. The lower border is the base of the mandible. It is smooth and rounded. The mental foramen, which transmits the mental vessels and nerves, is found about 1 inch from the symphysis and midway between the upper and the lower borders. The internal surface of the body of the mandible is concave from side to side and contains the mylohyoid line, which gives origin to the mylohyoid muscle. The angle of the mandible is that point at which the posterior border of the ramus joins the lower border of the body. It is subcutaneous and is easily felt 2 or 3 fingerbreadths below the lobule of the ear. The thin, sharp coronoid process gives attachment along its edges and on its deep surface to the temporalis muscle; the more posteriorly situated condyloid process articulates with the articular fossa on the infratemporal surface of the squamous temporal. Articular cartilage covers its superior and anterior aspects but not the posterior. The lateral aspect of the condyloid process is covered by the parotid gland, which is situated immediately in front of the tragus. When a finger is placed in front of the tragus, and when the mouth is alternately opened and closed, the movements of the condyloid process can be felt. The notch, situated between the coronoid and the condyloid processes, is known as the mandibular notch; it transmits the nerve and the vessels to the masseter muscle. About the center of the medial surface of the ramus of the mandible the mandibular foramen is found. It leads into a canal which passes downward and forward in the substance of the bone and carries the inferior alveolar vessels and nerve to the teeth. A spur of bone, known as the Ungula, usually
FIG Side view of the skull (norma lateralis). This part of the skull is formed by 5 bones: frontal, parietal, occipital, temporal and the great wing of the sphenoid. The face is situated below and in front.
FIG. Temporal and infratemporal region viewed from below.
overlaps this foramen. The mylohyoid groove, lodging the mylohyoid nerve and artery, commences behind the lingula and runs for about 1 inch obliquely downward and forward on the ramus.
NORMA LATERALIS
Some anatomy textbooks prefer to discuss a superior and an inferior temporal line, but these markings are so indistinct that the term “temporal line” is sufficient for surgical considerations. This line starts at the zygomatic process of the frontal bone, curves upward and backward and is easily felt on the living subject in its anterior and upper parts. Posteriorly, it curves downward and forward into the supramastoid crest. It gives attachment to the epicranial aponeurosis, the temporal fascia and the uppermost fibers of the temporalis muscle. The pterion is that region where the frontal, the great wing of the sphenoid, the parietal and the temporal bones meet. A point on the pterion about 4 cm. above the zygoma and 2.5 cm. behind the frontal process of the zygomatic bone overlies the anterior division of the middle meningeal artery. The infratemporal crest on the great wing of the sphenoid is a horizontal anteroposterior ridge which separates the temporal fossa above from the infratemporal fossa below. The temporal fossa is a wide space outlined by the temporal line and the zygomatic arch; it contains the temporalis muscle, its vessels and nerves and the zygomaticotemporal nerve. This is the thinnest and weakest region of the skull. Since the middle meningeal artery passes through here, many cases of fractures associated with injury to the vessel
FIG. X-ray study of the skull (lateral projection): (1) frontal sinus, (2) superior orbital plate, (3) orbit, (4) sphenoid sinus, (5) sella turcica, (6) lambdoid suture, (7) internal occipital tuberosity, (8) coronal suture, (9) middle meningeal channel (artery), (10) mastoid, (11) maxillary sinus, (12) odontoid process of axis, (13) atlas.
are common. The importance of and the approach to this region are discussed in a subsequent section. The infratemporal fossa is a wide space behind the maxilla, below the infratemporal crest and lateral to the pterygoid plates. It communicates with the temporal fossa through the gap which exists between the zygoma and the rest of the skull. The gap is traversed by the temporalis muscle as it descends to its insertion. The fossa contains the pterygoid muscles, the internal maxillary artery and its middle meningeal branch, the mandibular nerve and its branches, the chorda tympani nerve and the pterygoid venous plexus. Two fissures are present in the depth of the fossa: the infra-orbital fissure, which lies horizontally and connects the infratemporal fossa with the orbit; and the pterygomaxillary fissure, which is placed vertically and transmits the terminal part of the maxillary artery. The pterygomaxillary fissure leads medially into the pterygopalatine fossa. The zygomatic arch is quite evident and can be felt running from the prominence of the cheek to the tragus. It is formed by the zygomatic process of the temporal and the temporal process of the zygomatic bone. The tendon of the temporalis passes medial to the arch to gain insertion into the coronoid process of the mandible. The upper border of the arch gives attachment to the temporal fascia, and the lower border and medial surface give origin to the masseter muscle. The posterior root of the process is continued backward above the external auditory meatus as the supramastoid crest. Below the posterior root of the arch is an elliptical orifice known as the external auditory meatus, which is bounded in front, below and behind by the tympanic part of the temporal bone. Lateral to this and not seen in the dried skull, the cartilaginous segment of the external auditory meatus is attached. The bony meatus is barely wide enough to admit an ordinary pencil. It passes in a medial direction and slightly forward and opens into the middle ear in an oblique manner so that the tympanic membrane, which closes the opening, looks downward and forward as well as in a lateral direction. The outer orifice is also oblique, the upper margin overhanging the lower. The medial end of the meatus is closed during life by a tense vibrating membrane, called the tympanic membrane, which separates the meatus from the tympanic cavity (middle ear). Between the posterosuperior part of the meatus and the posterior root of the zygomatic arch the suprameatal triangle (Macewen) is found. It lies immediately behind the upper part of the external meatus and, although small and often inconspicuous, it is important because the tympanic antrum lies about 1/2 inch medial to it. The antrum is a cavity in the temporal bone which is surgically important in diseases of the mastoid process. This process can be palpated under cover of the lobule of the auricle. It is absent at birth and does not begin to appear until the 2nd year of life. A line drawn from one mastoid to the other passes immediately below the foramen magnum.
NORMA OCCIPITALIS
The back of the skull is horseshoe- shaped and extends from the tip of one mastoid process, over the vault, to the tip of the other. The bones that take part in its formation are parts of the 2 parietals, the occipital and the mastoid portion of the temporal, with its mastoid process. Some parts have already been seen from the norma verticalis, namely, the parietal eminences, the posterior part of the sagittal suture, the parietal foramina, the lambda and the lambdoid suture. The occipitomastoid suture descends between the occipital bone and the mastoid temporal. The mastoid foramen is seen on or near this suture and transmits an emissary vein which connects the veins on the outside of the skull with the sigmoid venous sinus. The external occipital protuberance (inion) is usually well marked in the median plane at the lower part of the back of the skull. It can be felt in the living person immediately above the nape of the neck and acts as a useful guide. The superior nuchal line is the curved ridge that arches laterally to either side of the protuberance. This protuberance, together with the right and the left superior nuchal lines, marks the division between the back of the head and the back of the neck. The lambda is the point of junction between the sagittal and the lambdoid sutures; it marks the position of the posterior fontanelle in the fetal skull.
INTERIOR OF THE SKULL
SKULL CAP
The inner aspect of the skull has a top part or skull cap and a floor or base. The skull cap is concave and presents depressions for the convolutions of the cerebrum and many furrows for the branches of the meningeal vessels. Along the midline is a longitudinal groove, narrow in front at the frontal crest, where it begins, but broader behind. This lodges the superior sagittal sinus, and its margins afford attachments for the falx cerebri. Bordering the sagittal groove, granular pits are seen which increase with age and occasionally are of sufficient depth to pass through the diploe to the outer table. They lodge and are eroded by the arachnoid granulations. In addition there are numbers of minute nutrient foramina.
BASE OF THE SKULL AND THE CRANIAL FOSSAE
The base of the skull on its inner surface shows a natural subdivision into 3 cranial fossae: anterior, middle and posterior. Since the anterior fossa is on a higher plane than
FIG. The upper surface of the base of the skull. The anterior fossa is on a higher plane than the middle fossa, and the middle is higher than the posterior; in this way three terraces are formed.
the middle, and the middle is higher than the posterior, there is a natural tendency toward the formation of 3 terraces. The anterior cranial fossa is limited posteriorly by the posterior edges of the lesser wings of the sphenoid and in the median part by the anterior edge of the optic groove of the sphenoid. It lodges the frontal lobes of the brain and the olfactory bulbs and tracts. The floor of the fossa is depressed in its median part, where it constitutes the roof of the nasal cavity. The median part is formed by the cribriform plate of the ethmoid bone, through which the crista galli, or cock’s comb, rises. It is an upward continuation of the nasal septum and gives attachment to the anterior end of the falx cerebri. The foramen caecum is a small pit found directly in front of the crista. In early life the superior longitudinal sinus communicates with the veins of the nose through this foramen, but in the adult it is usually closed, hence its name—caecum (blind). The cribriform plate is perforated like a sieve by numerous olfactory nerves, which are clothed in an arachnoid sheath and arise from the olfactory cells in the nasal mucosa. At the side of the cribriform plate the anterior and the posterior ethmoidal foramina are found. They mark the medial ends of two short canals that lead from the orbital cavity and open at the side of the cribriform plate; they transmit the anterior and the posterior ethmoidal arteries and the anterior ethmoidal nerve. The anterior ethmoidal artery and nerve, after passing through the foramina, run on the cribriform plate and then descend into the nose through the nasal slit which is found at the side of the front of the crista galli. Anterolateral to the median area, the roof of the frontal sinus and the roof of the orbit are found. Fractures of the anterior fossa may involve the cribriform plate and be accompanied by lacerations of the meninges and the mucous membrane of the roof of the nose. Such an injury gives rise to epistaxis, accompanied or followed by a discharge of cerebrospinal fluid. There may result some loss of smell due to laceration of the olfactory nervfcs as they pass upward from the nose and, if dural injury is present, it affords a route whereby infection can travel to the intracranial region from the nose. Meningitis or abscess in the frontal lobe may be a sequela of this type of fracture. If the cribriform plate does not heal after fracture and if a dural laceration remains unrepaired, there may be a continuous discharge of cerebrospinal fluid from the nose, known as cerebrospinal rhinorrhea. When the fracture involves the orbital plate of the frontal bone, subconjunctival hemorrhage is a characteristic feature, and the hemorrhage may seep within the orbit, producing an exophthalmos. The frontal sinus may also be involved. The middle cranial fossa is shaped like a butterfly, having a small median and two lateral expanded concave parts. The median part is formed by the upper surface of the body of the sphenoid. The sella turcica is the saddle-shaped area that accommodates the pituitary gland. Anteriorly is the ridge known as the tuberculum sellae, on either side of which is an anterior clinoid process. Immediately anterior to this process the optic foramen is situated at the end of the optic groove. The posterior part of the sella turcica is formed by the crest of the dorsum sellae, ending laterally in the posterior clinoid process The lateral part of the floor of the middle cranial fossa is formed by the greater wing of the sphenoid, the upper aspect of the petrous part of the temporal and a portion of the squamous part of the temporal bone. These lateral parts lodge the temporal lobes of the brain. The superior orbital fissure transmits to the orbital cavity the oculomotor, the trochlear, the ophthalmic division of the trigeminal and the abducens nerves, some filaments from the cavernous plexus of the sympathetic system and the orbital branch of the middle meningeal artery. From the orbital cavity this fissure also transmits the ophthalmic veins and a recurrent branch of the lacrimal artery to the dura mater.On either side of the sella is the carotid groove for the internal carotid artery. Three foramina run almost parallel with this groove. These are, from anterior to posterior and from medial to lateral: the foramen rotundum for the passage of the maxillary nerve, the foramen ovale for the mandibular nerve, the accessory meningeal artery and the lesser petrosal nerve, and the foramen spinosum for the passage of the middle meningeal vessels and a recurrent branch of the mandibular nerve. Medial to the foramen ovale is the foramen lacerum, a short, wide canal rather than a foramen, its lower part being filled by a layer of fibrocartilage. Its upper and inner parts transmit the internal carotid artery, which is surrounded by a plexus of sympathetic nerves. The petrous portion of the temporal bone forms a large and important part of the floor of the fossa. The highest part of this bone is known as the arcuate eminence and marks the position of the superior semicircular canal. Lateral to the eminence and immediately adjoining the squamous portion of the bone, the tegmen tympani is found. This is a very thin plate of bone which roofs the tympanic antrum, the tympanic cavity and the auditory tube. The important relationship of the thin tegmen tympani intervening between the inferior surface of the temporal lobe of the brain and the tympanic cavity cannot be overemphasized. This bone is the only barrier which exists between a diseased middle ear and the membranes of the brain or the brain itself. The hiatus for the greater superficial petrosal nerve is a small slit seen lower down on the anterior surface and about midway between the apex of the petrous temporal and the side of the skull. It communicates with the facial canal in the interior of the bone and transmits a slender nerve from which it takes its name. This nerve has its origin from the facial in the substance of the temporal bone and runs in a medial direction forward to the foramen lacerum. The trigeminal impression is found at the upper aspect of the apex of the petrous temporal and is represented by a slightly hollowed-out area. In it is lodged the trigeminal ganglion, which extends forward over the upper and the lateral parts of the foramen lacerum. The middle fossa is the commonest site of fracture of the skull because of its position and because it is weakened by numerous foramina and canals. Frequently, the tegmen tympani is fractured, and the tympanic membrane torn. Then blood and cerebrospinal fluid are discharged from the external auditory meatus and appear at the ear. The facial and the auditory nerves may be involved. At times the walls of the cavernous sinus are lacerated, and cranial nerves 3, 4 and 6, which lie in relation to its lateral wall, may also be injured. Fractures involving the middle cranial fossa may also pass through the sphenoid bone or the base of the occipital bone and cause bleeding into the mouth. The posterior cranial fossa is the largest and deepest of the cranial fossae and lodges
the hind brain (cerebellum, pons and medulla oblongata). Its floor is formed by the basilar, the condylar and the squamous parts of the occipital bone; its lateral wall, by the posterior surface of the petrous and the medial surface of the mastoid part of the temporal bone. The foramen magnum is the most prominent feature of the fossa. At the anterolateral boundary of the foramen the anterior condylar canal is found which transmits the hypoglossal nerve. This nerve arises by several roots of origin, and the canal is frequently divided into two parts by a small bar of bone. The foramen magnum transmits a number of structures, the most important being the medulla oblongata, the meninges, the vertebral arteries and the ascending parts of the accessory nerves. This foramen marks the lowest part of the posterior cranial fossa.
FIG.The two methods used to expose the brain, its coverings and vessels. Trephine operation: (A) skin flap formed, turned down and trephine in place; (B) removal of trephined “button” of bone; (C) incision into dura mater; (D) dural flap formed and reflected; (E) closure of dura. Osteoplastic craniotomy: (1) soft tissues incised, bone exposed and trephine openings made; craniotome divides the bone; (2) bone is fractured at the base of the flap; (3) dura is divided and underlying structures exposed; (4) dural closure.
FIG.Subtemporal decompression: (A) Line of incision and amount of bone to be removed; the incision is placed about three fifths of an inch in front of the tragus and extends upward and slightly backward for about 4 inches; (B) temporal muscle and fascia are incised, exposing temporal bone; (C) part of the temporal bone has been removed, and the dural hook has been placed; (D) dural opening enlarged on a grooved director; (E) and (F) are selfexplanatory.
The clivus is the broad, sloping surface that exists between the anterior margin of the foramen magnum and the root of the dorsum sellae; it is related to the pons and the medulla oblongata. The internal auditory meatus is found at the posterior aspect of the petrous temporal and runs laterally into the bone. Through it pass the motor and the sensory roots of the facial nerve, the auditory nerve, the internal auditory branch of the basilar artery and the auditory vein which joins the inferior petrosal sinus. The jugular foramen is situated between the lateral part of the occipital and the petrous part of the temporal bone. It is a large aperture with irregular margins and transmits three sets of structures. At times small spicules of bone project from its margin and may divide it partly or completely into corresponding compartments. The anteromedial compartment transmits the inferior petrosal sinus and a meningeal branch of the ascending pharyngeal artery. The middle compartment transmits the glossopharyngeal, the vagus and accessory nerves. The posterolateral compartment is larger than the other two and transmits the sigmoid sinus as it becomes the internal jugular vein, and a meningeal branch of the occipital artery. The inferior petrosal sinus, which passes through the anterior part of the foramen, becomes the internal jugular vein immediately outside of the skull. The transverse groove begins at the side of the internal occipital protuberance and sweeps around the cranial vault to the lateral end of the upper margin of the petrous temporal. It then joins the sigmoid groove, which curves downward and descends along the side wall of the skull and extends in a medial direction to end at the jugular foramen. The right transverse groove is wider than the left because it usually receives the sagittal sinus. The mastoid foramen is an aperture of variable size which leads from the exterior of the skull into the sigmoid groove on the side wall of the posterior cranial fossa. Through it a mastoid vein and the mastoid emissary vein and the mastoid branch of the occipital artery pass. The aqueduct of the vestibule (aqueductus vestibuli) is found about Vi inch lateral to the internal auditory meatus. Fractures of the posterior fossa are probably more important than such injuries in the other fossae, since it is here that a small fissure fracture may prove to be fatal. The bone is thin in places and, since there is no outlet for the escape of blood or cerebrospinal fluid as in the anterior and the middle fossae, these fractures may be overlooked. Some days after the injury, blood may be noted over the mastoid process. Fractures of the base of the skull involving the hypoglossal canal may be manifested by paralysis of one side of the tongue.
SURGICAL CONSIDERATIONS
TREPHINING OPERATIONS Two methods are usually employed to expose the brain: trephining and osteoplastic resection In trephining operations a circular disk of a cranial bone is removed by use of a trephine. The main indications for such operations are hemorrhage, abscess, fracture, evacuation of cerebrospinal fluid, or as a preliminary step to further brain surgery. A U-shaped or linear incision is made. If the former is used, its convexity is placed toward the crown of the head and the pedicle toward the base. The size of the flap is much larger than the bone which is to be removed. The incision passes through the skin, the superficial fascia, the muscle and the periosteum to the bone, and hemostasis is accomplished as the operation proceeds. With the trephine site cleared, a piece of bone is removed and, if a larger opening is needed, it may be obtained by removing pieces of bone from the circumference with a rongeur forceps. The dura is exposed and can be opened, but any large dural vessels should be ligated first. The necessary operative procedure is carried out, and the dural flap is sutured back into its normal position. The bone may or may not be replaced, and the wound is closed in layers.
OSTEOPLASTIC CRANIOTOMY Osteoplastic craniotomy implies the raising of a portion of skull which may be replaced when the operation is completed. Lateral, frontal, transfrontal, occipital and suboccipital osteoplastic flaps have been described, depending upon the area to be operated The incision passes through all the soft tissues down to the bone. Vessels are clamped and ligated, and the periosteum is detached for a short distance along the line of the contemplated bone incision. Openings are made along the bone margins by means of a drill, a burr or a small trephine, and the bone that intervenes is divided by a saw or rongeur forceps. The base of the pedicle is steadied, usually with the left hand. The upper portion of the flap is grasped with a cranial claw forceps, and with a quick jerk the bone is fractured. The flap thus created is turned back, and the dura is opened by means of a similar but smaller flap. The necessary operative procedure is carried out, the dura is closed by fine interrupted sutures, and the bone flap with its attached soft parts is replaced and sutured into position.
SUBTEMPORAL DECOMPRESSION A subtemporal decompression is really a craniectomy, which implies the removal of a portion of the skull, leaving a permanent gap. Such a procedure is necessary in about 10 per cent of all cases of severe head injuries where it is desired to give the brain room for expansion. The permanent bone defect should be covered over, if possible, by muscle so that a herniation of the brain does not result. Since the temporal muscle is conveniently situated, the decompression is usually made subjacent to it, hence the name “subtemporal decompression.” In this operation the skin incision, beginning at the zygoma, is placed three fifths of an inch in front of the tragus and extends upward and slightly backward for about 4 inches. The temporal fascia and muscle are incised to the bone in line with the scalp incision, the muscles and the fascia are retracted, and a piece of temporal bone a little over 2 inches in diameter is removed. The middle meningeal artery may cause troublesome bleeding The dura is palpated to determine the degree of tension; if it is high, the dura should be opened. However, some surgeons prefer to reduce the tension first by ventricular puncture. Sutures are placed in the muscle before the dura is opened but are not tied and may be brought together quickly to prevent rupture of the cerebral cortex. A fine hook is placed in an avascular dural area, which is incised. The dural opening may be enlarged by incising on a grooved director. If the tension is high, the brain protrudes with great force, and care must be taken to prevent a cortical rupture. As soon as the dura has been incised adequately, the muscles are brought together, followed by closure of the fascia and the skin.
INTRACRANIAL HEMORRHAGE A line known as the eye-ear line, or Reid’s base line, is utilized in cranial topography. It extends from the lower margin of the orbit to the upper border of the external auditory meatus. Some anatomists prefer to refer to a horizontal plane known as the
Extradural Hemorrhage. Extradural hemorrhage is usually caused by an injury to the middle meningeal artery or one of its branches. This vessel arises from the internal maxillary artery and enters the cranium via the foramen spinosum. It passes upward and forward for a short distance over the great wing of the sphenoid and soon divides into anterior and posterior branches, which ramify upon the dura and supply the greater part of its lateral and superior surfaces. The anterior branch, which is the larger, continues obliquely forward over the great wing to the antero-inferior angle of the parietal bone, in which it forms a deep groove. It ascends in this groove behind the anterior margin of that bone almost as far as the sagittal suture. The posterior branch passes upward and backward over the squamous portion of the temporal bone. The artery is accompanied by its two venae comites. The anterior branch is found readily through an opening which is made 1 1/2 inches behind the external angular process of the frontal bone and a similar distance above the upper border of the zygoma. This is the branch that is damaged most frequently and, since it is closely related to the motor area of the cortex, injury to it might produce a loss of power in the muscles of the opposite side of the body. The posterior branch can be reached through a trephine hole 1 inch above the external auditory meatus (the midmeatal point). In ligating the middle meningeal artery, either a vertical or a horseshoe-shaped incision can be used. The skin incision should be continued vertically downward toward the zygoma, and the temporal muscle is divided. Only when the bone opening is sufficiently large should the clot be removed; this usually requires an opening of about 2 inches in diameter. The bleeding vessel is located and ligated by passing a needle about it, clamping with a Cushing clip or coagulating with an electrosurgical needle. The muscle, the fascia and the skin are closed with fine sutures. Drainage is not indicated in these cases.
Subdural Hemorrhage. When subdural hemorrhage is present, it might become necessary to explore through a trephine opening to locate the point of hemorrhage. After the skull has been opened, the dura is tense and plum colored, signifying extravasated blood beneath it. The exploratory trephine hole is enlarged, the dura is opened, and necessary hemostatic measures are carried out.
FIG. Extradural hemorrhage: (A) cranial topography, location of the anterior and posterior branches of the middle meningeal artery; (B) incision for ligation of the middle meningeal artery; (C) extradural hematoma located and vessel clamped.
MENINGES
FIG Diagrammatic frontal section through the scalp, the skull, the meninges and the brain. The arachnoid villi invade the dura, and the subarachnoid space is trabeculated. The 4 intracranial spaces should be noted.
FIG The 4 membranes formed by the infolding of the dura mater (falx cerebri, falx cerebelli, tentorium cerebelli and diaphragma sellae). The venous sinuses and the cranial nerves are also shown.
The brain and the spinal cord are surrounded by three enveloping membranes, which are known from inside out as the pia mater, the arachnoid mater and the dura mater. Their names suggest their qualities: the dura is tough and firm, the arachnoid resembles a spider’s web, and the pia represents a very thin, clinging, skinlike structure that hugs the surface of the brain and follows its irregularities. The dura and the arachnoid do not dip into the fissures but fit the brain as a child’s mitten fits its hand; on the other hand, the pia mater dips into each fissure and fits the brain very much as a glove fits the hand, since each finger has its own indentation (see venous sinuses of the dura mater.The dura mater is the most external membrane of the brain; it consists of two layers that are firmly blended with each other except in certain locations. The more superficial of these layers is the endocranium, which is a periosteum (endoperiosteum). Through the openings in the skull it is continuous with the external periosteum (pericranium). The endoperiosteum is the layer that is intimately related to the bones of the skull and io way takes part in the formation of the falx cerebri or the tentorium cerebelli. Bulging arachnoid granulations (enlarged villi of the arachnoid projecting through the layers of the dura mater) project from each side of the median sagittal plane and produce the pits found on the parietal bone. The middle meningeal vessel ascends in the dura and produces a groove in the parietal bone. The deeper or inner layer of dura is smooth and lined by endothelial cells. It resembles a serous membrane and is separated from the superficial layers by a small amount of fibrous tissue. The venous sinuses and the meningeal vessels separate the 2 layers of dura. By a process of infolding and reduplicating itself, the inner layer of dura forms 4 membranes that subdivide the cranial cavities. These membranes are the falx cerebri, the falx cerebelli, the tentorium cerebelli and the diaphragma sellae. The sickle-shaped falx cerebri is placed vertically between the 2 hemispheres of the cerebrum and is a reduplication of the inner layer of the dura. It consists of 2 layers of serous dura. Its upper border is convex and attached to the crista galli in front; it extends back to the internal occipital protuberance and between these two points is attached to the internal surface of the skull. Its lower border is attached to the tentorium cerebelli behind but otherwise remains free to project between the cerebral hemispheres in front of the tentorium. The falx is narrow in front and becomes wider as it is traced backward. The superior sagittal sinus appears in its upper border; its lower border contains the inferior sagittal sinus and aids the tentorium in the support of the straight sinus. The falx cerebelli passes vertically from the tentorium to the foramen magnum and separates the 2 cerebellar hemispheres. It attaches posteriorly to the internal occipital crest, where it encloses the occipital sinus. Construction of the falx cerebells exactly the same as that of the falx cerebri.
FIG. Coronal section through the foramen magnum, showing the relationships of the meninges, the venous sinuses and the blood vessels.
The tentorium cerebelli is a tentlike fold of a double layer of serous dura mater, forming a partition between the cerebellum and the posterior part of the cerebral hemispheres. It forms a roof for the cerebellum and a floor for the occipital lobe and the posterior part of the temporal lobe of the cerebrum. Anteriorly, a wide gap known as the tentorial notch permits the passage of the midbrain. Because of this arrangement the tentorium possesses a free inner and an attached outer border. This outer border has 3 attachments: to the margins of the groove of the transverse sinus of the occipital bone; to the margins of the groove for the superior petrosal sinus on the petrous portion of the temporal bone; to the posterior clinoid process of the sphenoid bone. The free border runs forward to the anterior clinoid process, and the upper layer of the tentorium becomes continuous with the falx cerebri in the median plane. The diaphragma sellae is also a fold of inner layer of dura mater with a foramen in its center. Its lateral border is attached to the clinoid processes; its medial border forms the boundary of the foramen of the diaphragma sellae and also surrounds the infundibulum. The superior surface of the diaphragm is in relation to the base of the brain; its inferior aspect is related to the hypophysis, which is bound by it to the hypophyseal fossa. The arachnoid mater, a delicate membrane enveloping the brain and medulla spinalis, lies between the pia mater internally and the dura mater externally. It does not dip into the various sulci on the surface of the brain, but is carried into the longitudinal fissure by the falx cerebri. Over the convolutions the arachnoid and the pia are in close contact but are separated at the sulci by the subarachnoid space, which contains the cerebrospinal fluid and is crossed by a gauzy retinaculum of cobweblike fibers connecting the two membranes. At the base of the brain this network is much reduced and the two membranes are widely separated to form the so-called subarachnoid cisternae. The three main cisternae are: 1. The cisterna cerebromedullaris (cisterna magna) is a cavity resulting from the arachnoid’s bridging the inferior surface of the cerebellum and the dorsal surface of the medulla oblongata. It is continuous below with the spinal subarachnoid space. Cerebrospinal fluid passes directly into this cistern from the fourth ventricle by means of the foramen of Magendie (median aperture). 2. The cisterna ponds, a space lying in front of the pons and the medulla oblongata, is continuous with the subarachnoid space about the medulla and has been referred to as “Hilton’s water bed,” since it forms a water cushion to protect the brain. The roots of the lower 8 th cranial nerves traverse this cavity. 3. The cisterna interpeduncularis, a wide cavity formed by the arachnoid as it extends across and between the two temporal lobes, encloses the cerebral peduncles and contains the arterial circle of Willis. Some consider it part of the cisterna basalis, which connects it to a smaller cisterna in front of the optic chiasma. The arachnoid granulations are seen best in old age, where they produce pitting of the parietal bone. When hypertrophied, they are called pacchionian bodies. Although they appear to originate in the dura, they are really villous processes of the arachnoid that push the dura mater ahead of them. They serve as channels for the passage of cerebrospinal fluid into the venous system and at times may become large enough to produce pressure signs. The pia mater is the innermost of the three meninges and is in reality the membrane of nutrition. It is closely attached to the surface of the brain and dips into the depths of all the sulci, carrying branches of the cerebral arteries with it. The larger blood vessels of the brain lie in the subarachnoid space, but the smaller ones ramify the pia and proceed into the substance of the brain proper. At certain locations the pia mater sends strong vascular duplications into the brain; these spread over the cavities of the third and the fourth ventricles and are known as the choroid telae. The choroid tela of the 3rd ventricle extends into each lateral ventricle. The blood vessels on the border projecting into the lateral ventricle are enlarged into a plexus known as the choroid plexus of the lateral ventricle, from which the greater amount of cerebrospinal fluid is formed.
INTRACRANIAL SPACES
The 4 intracranial spaces are: the extradural (exterior to the dura); subdural (beneath the dura); subarachnoidal (beneath the arachnoid); the intracerebral (within the brain tissue proper). 1. The extradural space is only a potential one because the dura touches the internal surface of the skull. The meningeal vessels are in this space, and if they are injured, bleeding takes place between the dura and the skull. If this bleeding is permitted to continue, the dura is slowly stripped away from the bone. Bleeding into this space is usually arterial and therefore rapid and often fatal. If the arachnoid is intact and the subarachnoid space has not been entered, there is no blood in the cerebrospinal fluid. 2. The subdural space is situated between the dura and the arachnoid. Hemorrhage into this space may result from injury to large arteries such as the middle cerebral or internal carotid, but this is rare, rapidly fatal and of no practical importance. It is much more important to consider subdural hemorrhage as venous, since the large sinuses, such as the superior longitudinal and lateral, may be torn when the dura is injured. If the arachnoid is also torn, as it may be over the great cisterns at the base of the brain, blood escapes into the subarachnoid space and will appear in the cerebrospinal fluid. 3. The trabeculated subarachnoid space is situated between the arachnoid and the pia mater; cerebrospinal fluid circulates here. The space is not wide over the convexity of the brain, but is quite extensive at the base of the skull where the cisternae are formed. These form a “water bed” of subarachnoid fluid upon which the brain floats. Only the anterior third of the brain rests directly upon bone (the orbital plates of the frontal bone). 4. Involvement of the intracerebral “space” is really involvement of brain substance proper. Theoretically, the subpial space is that potential interval that exists between the pia and the brain and is of no practical importance. Attempts to strip the pia mater from the brain are often unsuccessful, since brain tissue comes away with the intimately attached pia. Bleeding into the brain proper may be traumatic in origin or may be the result of spontaneous rupture of an artery in its interior. Since the pia is frequently torn with these hemorrhages, frank blood appears in the cerebrospinal fluid.
VENTRICULAR SYSTEM AND CEREBROSPINAL FLUID
The circulation of the cerebrospinal fluid is associated with (1) the ventricular system and (2) the subarachnoid space. The spinal fluid is formed in the ventricular system and absorbed in the subarachnoid space. The ventricular system (Fig. 24) is composed of four ventricles, two of which are lateral. Normally, these spaces communicate freely with each other through well-defined openings. Each lateral ventricle is situated within a cerebral hemisphere and is subdivided into an anterior horn (in the frontal lobe), a body (in the parietal lobe), a posterior horn (in the occipital lobe), and a descending horn (in the temporal lobe). Each communicates with the third ventricle by a single opening known as the foramen of Monro. This foramen has a V-shaped arrangement of two limbs, each draining its respective lateral ventricle. It is situated in the anterior horn and is the only means of exit for the lateral ventricles. The 3rd ventricle empties into the 4th by means of the infant.
FIG.The ventricular system. The horns and the body of the first and the second lateral ventricles are pictured in relation to the brain.
A spina bifida is also present. aqueduct of Sylvius, which is about 1\2 inch long and quite narrow, being only slightly larger than the lead of a pencil. This aqueduct, passing through the midbrain, enters the anterior part of the 4th ventricle; it is the only source of exit for the 3rd and both lateral ventricles. Because of its location and its small size, it is the weakest and most important point of the entire ventricular system. The 4th ventricle is situated in the posterior cranial fossa, the cerebellum forming its
roof and the pons and the medulla its floor. It connects with the subarachnoid space by three openings: the two lateral foramina of Luschka and a median foramen of Magendie. The two lateral foramina of Luschka open into the cisterna lateralis, and the foramen of Magendie into the cisterna magna (cisterna cerebellomedullaris). In this way the ventricular system becomes connected with the subarachnoid space. The fluid, having gained entrance into this space and the cisternae, circulates freely around the cerebrum and the cerebellum, finally passing down the spinal subarachnoid space.
Cerebrospinal fluid is formed by the choroids plexus, mainly in the lateral ventricles; from this point it passes through the foramen of Monro into the 3rd ventricle and finally into the subarachnoid space, where it comes in contact with the arachnoid villi, which absorb it and return it to the venous stream in the dural sinuses. The total amount of cerebrospinal fluid has been estimated to be between 90 and 150 cc. in adults. If there is a block along the route of the ventricular system, the condition of hydrocephalus results. If such a block is located at a lateral ventricle entrance into the 3rd ventricle, distention of one ventricle would result; if the block is at the aqueduct of Sylvius, a distention of both
FIG. Ventriculography
Two small incisions are made 1 inch to each side of the midline and 2 inches above the lambdoid suture. Two burr holes are placed at these points, and the dura is nicked. Then a ventricular needle is introduced into the lateral ventricle at the junction of the body and the occipital horn. Cerebrospinal fluid is replaced with air.
lateral and the 3rd ventricles would result; if the obstruction is at the openings in the 4th ventricle (Magendie and Luschka), distention of all ventricles will ensue. The type of block may be determined by ventriculography.
FIG.B. Encephalogram in anteroposterior projection: (1) anterior horn, (2) body of the lateral ventricle, (4) third ventricle, (8) orbit, (9) nasal septum, (10) inferior turbinates.
SURGICAL CONSIDERATIONS
Two procedures, ventriculography and encephalography, are valuable diagnostic aids, especially in the localization of brain tumors and obstruction of the ventricular system ENCEPHALOGRAPHY Encephalography consists of withdrawing cerebrospinal fluid by means of a lumbar puncture needle and introducing air. The air slowly ascends and produces an outline of the ventricular system which can be seen on a roentgenogram. It is important to utilize a manometer during the procedure so that the cerebrospinal pressure is measured. As a rule, from 20 to 25 cc. of air is introduced; the outlines of the ventricles are seen, and any abnormality is noted. Encephalography should not be used when there is an increase in intracranial pressure. VENTRICULOGRAPHY Ventriculography is a more formidable procedure but is the method of choice. It involves two incisions and two perforations of the skull. The technic consists of making two small incisions in the scalp about 1 inch on either side of the mid-line and about 2 inches above the lambdoid suture. The lips of each incision are retracted, and a small burr hole is made. The dura is exposed, carefully nicked with a small crucial incision, and a ventricular needle is introduced. This is passed downward, forward and inward in such a way that the lateral ventricle is entered in the region of the junction of its body with the occipital horn. Thus, a study of the cerebrospinal fluid
FIG.C. Encephalogram in postero-anterior projection: (2) body of the lateral ventricle, (3) posterior horn, (5) descending horn.
is permitted, as well as temporary relief from intracranial pressure. Fluid is removed and replaced by a somewhat smaller volume of air, the average amount of air injected being from 50 to 120 cc. After this, lateral and anteroposterior roentgenograms are taken
(Fig. A and B). The lateral view may show deformity of the anterior or the posterior horns by tumors situated in the frontal or occipital regions. The anteroposterior view may reveal a deflection of the ventricles from the midline or a filling defect of the third ventricle. During this procedure it is best to have the patient in the sitting or semisitting position.
CISTERNAL PUNCTURE In cisternal puncture (Fig. 28) the patient may be in a sitting position or lying on one side with the head placed somewhat forward. The first palpable cervical spinous process is located in the midline, and a point is taken immediately above it. The needle is then inserted in a forward and upward direction. The upward path parallels an imaginary line that joins the external auditory meatus with the nasion; as the needle advances it strikes the posterior occipito-atloid ligament. In the adult this is at a depth of between 4 and 5 cm. Piercing of the ligament by the needle is usually felt, and then the cistern is entered. The medulla is about 1 inch anterior to the posterior occipitoatloid ligament.
ARTERIAL SUPPLY The arterial supply of blood is furnished to the brain by 4 vessels: 2 vertebral and 2 internal carotid arteries. The vertebral artery, a branch of the subclavian, after ascending and perforating the dura, unites with the same vessel of the opposite side to form the basilar. This vessel lies in the basilar groove of the pons and at its superior margin divides into 2 terminal branches known as the posterior cerebral arteries. The internal carotid, after penetrating the dura, reaches the base of the brain
FIG.Cisternal puncture. An imaginary line is constructed between the external auditory meatus and the nasion. The needle enters above the spinous process of the 1st cervical vertebra, parallels this line and enters the cisterna magna. The medulla is about 1 inch anterior to the posterior occipito-atloid ligament.
FIG.The arterial supply as seen from the base of the brain, and the formation of the circle of Willis. The cranial nerves are shown in relation to the vessels.
at the angle between the optic nerve and the optic tract, then divides into 2 branches: anterior and middle cerebral arteries. These are connected by communicating vessels to form the arterial circle of Willis, which lies within the interpeduncular subarachnoid cistern. The arterial circle is formed in the following way: anteriorly, the anterior communicating artery joins the 2 anterior cerebral arteries, and the posterior communicating artery connects the internal carotid with the posterior cerebral artery; posteriorly, the basilar artery bifurcates into the two posterior cerebral arteries to complete the circle. The so-called circle is really heptagonal in shape. Two separate sets of branches arise from the cerebral arteries: (1) the central branches, which are very numerous and slender, pierce the surface of the brain to supply the internal parts of the cerebrum, including the basal nuclei, and do not anastomose with one another; (2) the cortical branches ramify over the surface of the cerebrum and supply the cortex, anastomose in the pia, and are not sharply cut off from one another. The anterior cerebral artery supplies the superior and the middle frontal convolutions and the entire medial surface of the hemisphere as far back as the parieto-occipital fissure. It also supplies the leg center of the paracentral lobule and the highest point of the precentral convolution. The middle cerebral artery is a direct continuation of the internal carotid; it runs upward and outward to the Sylvian fissure and supplies most of the exposed surface of the hemisphere, the insula and the internal capsule. It also supplies the bulk of the motor area of the brain, the cortical center for hearing, part of the center for vision and the
FIG. Veins of the head and the brain. Three of the emissary veins (parietal, mastoid nd ophthalmic) are shown with their intracranial communications. Since the blood flow can travel in either direction, infection may also pass both ways. The angular vein, which drains the upper lip or “dangerous area of the face,” is of particular importance because of its communication with the cavernous sinus.
motor speech area of the left hemisphere. It gives off the lenticulostriate artery, which is the vessel most frequently ruptured in cases of cerebral hemorrhage. This vessel has been referred to as the “artery of apoplexy” (Charcot). The posterior cerebral artery supplies the middle and the inferior temporal gyri, the medial part of the occipital lobe and the lower surface of the temporosphenoidal lobe.
VEINS OF THE HEAD AND THE BRAIN
The veins of the head and the brain may be divided as follows: (1) the emissary veins, which connect the veins of the inside of the skull with those of the head, the face and the neck; (2) the diploic veins, which form venous plexuses situated between the inner and the outer tables of the skull; (3) the cerebral and the cerebellar veins, which drain the venous blood of the cerebrum and the cerebellum; (4) the venous dural sinuses, which are placed between the layers of the dura mater.
EMISSARY VEINS The emissary veins connect the intracranial and the extracranial veins. Since blood may flow in either direction, infection may also travel both ways. This double direction of blood flow equalizes the venous pressure in the sinuses and the superficial veins. The more important emissary veins include: 1. The parietal vein, which passes through the parietal foramen at the top of the skull and joins the occipital vein via the superior sagittal sinus. It is of marked surgical importance as the path by which a relatively simple scalp infection may result in a thrombophlebitis or sinus thrombosis involving the superior sagittal sinus. 2. The emissary veins of the foramen caecum connect the beginning of the superior sagittal sinus with the veins of the frontal sinus and the root of the nose. By means of this route infection may travel from either of the latter two structures to the superior sagittal sinus. These veins are seen more constantly in children than in adults. 3. The mastoid is the most constant of the emissary veins; it connects the occipital or posterior auricular vein with the transverse (lateral) sinus. It is of surgical importance because of the frequency with which mastoid disease takes place and may result in infection of the transverse (lateral) sinus. 4. The ophthalmic veins are considered as emissary veins which drain into the cavernous sinus. Blood can flow in the reverse direction in these vessels and pass to the face and infratemporal fossa. It is in connection with these emissary veins that the anterior facial vein becomes of utmost importance, the latter communicating with the cavernous sinus through the ophthalmic veins. The anterior and the posterior facial veins join in the neck to form the common facial vein, which pierces the deep fascia and ends in the internal jugular; at times it may cross the sternocleidomastoid muscle and end in the external jugular vein. That part of the anterior facial vein which passes along the side or angle of the nose has been called the angular vein. It is important because it drains the so-called “dangerous area of the face.” Boils and carbuncles commonly occur in this region and should such lesions be opened, death may result from involvement of the cavernous sinus; the internal jugular vein may also become infected in such cases. Since these veins have no valves, infected thrombi become detached as a result of the constant motion brought about by talking and masticating, causing a spread of the infection into the interior of the skull. There are other emissary veins that are of less practical importance, namely, the veins of the hypoglossal canal, the condyloid canal, the foramen ovale, the foramen lacerum, the foramen of Vesalius and the emissary veins accompanying the middle meningeal artery.
DIPLOIC VEINS The diploic veins form venous plexuses between the inner and the outer tables of the skull. In the skull of the child the bone consists of a single layer in which numerous veins grow and communicate with each other. Marrow is found around these branching and communicating vessels, and this ingrowth results in the formation of an outer table of skull, an inner table and the diploe situated between them. The veins form a plexus that is drained by four diploic venous trunks on each side: the frontal diploic vein drains into the supra-orbital vein; the anterior parietal {temporal) drains into the sphenoparietal sinus; the posterior parietal {temporal) drains into the lateral sinus; the occipital also drains into the lateral sinus. Diploic markings may be confused with fractures on a roentgenogram of the skull In the parietal region the socalled “parietal spider” is seen, a spiderlike arrangement of these veins. There are no diploic arteries, since the arterial blood supply comes by way of the meningeal and the pericranial arteries.
CEREBRAL AND CEREBELLAR VEINS The cerebral and the cerebellar veins are veins of the brain proper. They do not accompany the arteries; they have no valves, no muscle tissue around them, and their walls are extremely thin. They are lodged for the greater part in the grooves on the surface of the brain and are covered by arachnoid. The superior veins run upward toward the superior sagittal sinus, turn forward and run parallel with the sinus for a short distance before entering it. The cerebral veins are divided into external and internal groups, depending upon whether they drain the outer surface or the inner part of the hemisphere. The external veins are named the middle, the superior and the inferior cerebral veins. The internal veins draining the deeper parts of the hemisphere are the terminal ones and the great cerebral vein of Galen.
VENOUS DURAL SINUSES Venous sinuses of the dura mater are spaces between the 2 layers of dura mater which collect blood and return it to the internal jugular vein. Into these spaces spinal fluid is also drained from the subarachnoid space through the arachnoid villi and granulations. Sinuses differ from other venous structures in the body in that their walls consist of a single layer of endothelium, as a result of which there is no tendency for them to collapse. Seven of these sinuses are paired, and 5 are unpaired. The unpaired sinuses are the superior sagittal,
FIG.The diploic veins. These veins form venous plexuses between the outer and the inner tables of the skull. Four diploic venous trunks drain these plexuses. The outer table of compact bone has been removed to demonstrate the veins.
inferior sagittal, straight, intercavernous and basilar. The paired sinuses are the sphenoparietal, cavernous, superior petrosal, inferior petrosal, occipital, transverse and sigmoid. Only those that are of practical and surgical importance will be considered. The superior sagittal (longitudinal) sinus is in a somewhat exposed position along the insertion of the falx cerebri. It begins in front of the crista galli at the foramen caecum, where it occasionally communicates with the veins of the nasal mucous membrane. It then passes upward and backward in the upper border of the falx cerebri until it reaches the internal occipital protuberance, where it lies a little to one side of the median plane, usually on the right. Here it forms a dilatation known as the confluence of sinuses (torcular Herophili), at which point the superior sagittal, the transverse, the occipital and the straight sinuses all meet. Here the superior sagittal bends acutely to theright, occasionally to the left, and becomes continuous with the transverse sinus. Lateral expansions of the sinus (lacunae lateralis) are found on each side. These lacunae receive meningeal and diploic veins, and the superior sagittal sinus receives emissary veins, diploic veins and those veins which drain the cerebral hemispheres. As the superior sagittal sinus runs posteriorly, it grooves the internal aspect of the skull, and its surface marking may be indicated by a line drawn over the median line of the vertex from the root of the nose to the external occipital protuberance. The inferior sagittal sinus passes backward in the lower border of the falx cerebri. It unites with the great cerebral vein at the free margin of the tentorium cerebelli to form the straight sinus. The straight sinus travels backward along the attachment of the falx cerebri to the tentorium. At the internal occipital protuberance it bends acutely to the left, occasionally to the right, to form the tranverse sinus. It receives tributaries from the posterior part of the cerebrum, the cerebellum and the falx cerebri. The transverse {lateral) sinus, which is a paired structure, begins at the internal occipital protuberance. The right is usually continuous with the superior sagittal sinus and the left with the straight sinus. It receives the superior petrosal sinus and a few inferior cerebral and cerebellar veins. It is bounded by the 2 layers of tentorium and the outer layer of dura mater and runs horizontally at first in a lateral direction and then forward. It lies in the transverse groove of the skull and in the attached margin of the tentorium.
The sigmoid sinus is a continuation of the transverse sinus and receives its name from the S-shaped curves which it makes. Some authors believe the term “transverse” should be restricted to that part of the sinus that passes between the internal occipital protuberance and the posterior inferior angle of the parietal bone. The remaining part of the
FIG. 33. The cerebral veins, viewed from above. The superior sagittal sinus has been opened, and the dura mater has been reflected on the left side, exposing the subdural space. The intact dura on the right side reveals the relationship of the extradural space and the middle meningeal vessels. A small flap of arachnoid has been reflected to show the position of the cerebral veins.
FIG.Venous sinuses at the base of the skull. The right internal carotid artery is shown surrounded by the cavernous sinus.
sinus (to the jungular foramen) is known as the sigmoid sinus, which curves downward, leaves the tentorium, passes between the two layers of dura and ends at the jugular foramen, where it becomes the internal jugular vein. The continuation of the sinus as the internal jugular explains the propagation of a transverse sinus thrombosis. This justifies the ligation of the internal jugular to prevent the spread of septic emboli to the heart. The superior petrosal sinus joins it at its first bend, and the inferior petrosal at its termination. It forms an important posterior relation of the tympanic antrum. In suppurative conditions of the tympanic antrum or cavity this sinus may become the site of a septic process that travels through the cerebellar tributaries and forms a cerebellar abscess. It is separated from the mastoid cells by only a very thin plate of bone; hence, diseases from the middle ear into the mastoid cells can form a suppurative process that involves the sinus (sinus thrombosis). Its communications are numerous and important; it is connected by the mastoid emissary vein with the occipital vein, by the occipital sinus with the transverse sinus and by the posterior condylar emissary vein with the suboccipital plexus. The cavernous sinus is situated to either side of the body of the sphenoid bone and is continuous with the ophthalmic veins in front. Posteriorly, it divides into the superior and the inferior petrosal sinuses. It surrounds the internal carotid artery. Injury in this area may result in the formation of an arteriovenous aneurysm which produces stasis in the superior ophthalmic vein. This may bring about a pulsating exophthalmos due to pulsations of the cartoid artery transmitted to the engorged venous spaces. Cavernous sinus thrombosis may follow inflam- matory lesions of the face and the upper lip, the extension taking place through the facial, the nasal and the ophthalmic veins. This sinus is intimately related to the gasserian ganglion and may be injured during operations on the latter. Infections involving the cavernous sinus are frequently accompanied by basilar meningitis. The circular sinus consists of the two transverse venous connections between the cavernous sinuses. The sphenoparietal sinus runs along the lesser wing of the sphenoid to the superior sagittal sinus. The occipital sinus is extremely variable in size and lies in the attached border of the falx cerebelli. The basilar sinus is a wide trabeculated space behind the dorsum sellae which unites the cavernous and the inferior petrosal sinuses of opposite sides. It also communicates below with the spinal veins.
Cranial Nerves (table)
RECOMMENDED LITERATURE:
1. Mark W. Wolcott. Ambulatory Surgery End The Basic Of Emergency Surgical Care.-Philadelphia:J.B.Lippincott Company,2001.-752p.
2. Michael F. Mulroy.Regional Anesthesia /The
3. Richard M. Stilman,M.D.,E.A.C.S. General Surgery /Review And Assessment/
4. Kent M. Van De Graff, Stuart Ira Fox, Karen M. Lafleur. Synopsis of Human Anatomy and Physiology /WCB McGraw-Hill/, 2004.-675p.
5. John J. Jacobs. Shearer’s Manual Of Human Dissection /McGraw-Hill Information Services Company, 1998.-300p.
6.
7. Philip Thorek. Anatomy In Surgery /J.B.Lippincott Company/,1996.-935p.
