Employment 3. Topographical Anatomy of Temporal Region. Topographical
Anatomy of the Lateral Facial Region of the Head. Surgical Anatomy of the
Parotid Gland, the Parapharyngeal Space. The Facial Nerve Branches, the
Parotid Duct. Incisions in Case of Purulent Parotitis.
Topographical Anatomy of Facial Deep Region. The Anatomical Basement and Technique of Block Anesthesia of
Trigeminal Nerve Branches. Operations in Case of
Chronic Frontitis and Maxillitis.
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.
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.
Facial region of the Head
EMBRYOLOGY
At the anterior end of the embryo an opening called
the stomodeum appears during the latter part of the first month of
intra-uterine life. The face is formed from five processes surrounding this
opening: one frontonasal, two maxillary and two mandibular processes. The
mandibular processes grow medially, fuse and unite in the midline, forming the
lower jaw or mandible. When a failure of fusion of these
processes occurs, a fissure of the lower lip results. The fusion of the
upper processes converts the single stomodeal orifice into the cheeks, the
whole upper lip except the philtrum (the vertical groove in the middle of the
upper lip), most of the upper jaw and the palate. The appearance of an
olfactory pit divides the frontonasal process into a medial and two lateral
nasal processes. The medial process forms the septum of the nose, the philtrum
and premaxilla; the lateral processes form the side of the nose but take no
part in the formation of the upper lip. By imperfect fusion various defects
result, such as harelip, macrostoma, microstoma, cleft palate, etc.
SKIN,
BLOOD AND NERVE SUPPLY
Skin. The
skin of the face is thin, vascular, movable and
abundantly supplied with sebaceous and sweat glands. The absence of deep fascia
in the anterior aspect of the face permits muscles arising from the bone to be
inserted directly into the skin. The glands situated in the skin lie in
immediate relationship to the subjacent loose areolar tissue, and it is the
presence of this loose tissue, unsupported by deep fascia, that permits
therapid spread of edema. Over the lower part of the nose, however, the skin is
firmly bound to the underlying cartilage, and inflammations here are extremely
painful. The skin over the chin resembles the integument of the scalp in that
it is very dense and adherent to the parts beneath. Because of its mobility and
vascularity, the skin of the face is especially adaptable to plastic operations
and sound healing. The "dangerous area" of the face is triangular and
bounded by lines that join the root of the nose with the angles of the mouth.
The venous drainage from this area enters the angular vein, which communicates
with the cavernous sinus via the superior ophthalmic vein. Therefore, boils or
carbuncles in this region may produce a cavernous sinus thrombosis.
Blood
Supply. The blood
supply of the face is free, and anastomoses are numerous. The arterioles have a
rich supply of sympathetic vasomotor nerves from the superior cervical
ganglion, and because of this, blushing and blanching occur readily in
emotional states. The main artery of the face is the facial (external
maxillary), which is a branch of the external carotid. It appears at the
base of the jaw immediately in front of the masseter muscle, passes upward in a
tortuous manner toward the angle of the mouth and the side of the nose, and
terminates near the inner canthus of the eye, where it anastomoses with the
nasal branch of the ophthalmic artery. It crosses the lower jaw, the buccinator
muscle, the upper jaw and the levator angulis oris; it is covered superficially
by the platysma, the risorius, the zygomaticus major and minor and the levator
labii superioris. In its lower part the artery rests directly on the mandible
and is covered only by skin and the risorius muscle. Leaving the mandible, it
travels on the surface of the buccinator and a little higher is crossed by the
zygomaticus major muscle. In the interval between these two muscles it is
covered only by skin and superficial fascia. Its accompanying veins lie behind
it on the masseter. The cervical branch of the facial nerve enters the face
superficial to the artery. A rich anastomosis occurs between the vessels of the
two sides, and an additional anastomosis exists between the facial artery and
the arteries which accompany the cutaneous branches of the 5th nerve on the
face (ophthalmic and internal maxillary arteries). The facial artery supplies superior
and inferior labial arteries which pass medially in the upper and
the lower lips; they are situated in the submucous tissue about XA inch
from the mucocutaneous junction, where their pulsations can be felt easily.
Each anastomoses with its fellow of the opposite side and forms an arterial
ring around the lips. During operations these vessels may be controlled by
grasping the lip between the fingers and the thumb. The superior labial artery
supplies a small branch to the nasal septum. Because of the marked vascularity,
extensive areas of facial skin, torn in lacerating wounds, often retain their
viability and may be sutured back into place. The anterior facial vein is
the companion vein of the facial artery. It is formed near the inner angle of
the eye by the union of the supra-orbital and supratrochlear veins and passes
behind the artery, taking a less tortuous but more superficial course. It makes
three important connections: with the diploic veins through the frontal diploic
veins; with the pterygoid plexus through the deep facial veins; and with the
cavernous sinus through the superior ophthalmic vein. The vein itself
terminates in the internal jugular vein. The important relationship between
this vessel and the "dangerous area" of the face has been stressed.
Nerves. The
nerves of the face are branches of the facial, which supplies the
muscles of expression, and the trigeminal, which supplies the integument
and the muscles of mastication. The entire skin of the face, with the exception
of the area over the lower half of the ramus of the mandible, which is supplied
by the great auricular nerve, is innervated by the 3 divisions of the
trigeminal nerve. Since the face is developed from 3 rudiments, the
frontonasal, the maxillary and the mandibular processes, each possesses its own
sensory nerve. These nerves make up the 3 divisions of the trigeminal: the
ophthalmic, the maxillary and the mandibular. The ophthalmic, or first
division of the trigeminal nerve, has 5 cutaneous branches:
(1) The supra-orbital
nerve leaves the orbit through the supra-orbital notch or foramen about 2
finger-breadths from the median line. It divides into lateral and medial
branches which supply the central portion of the upper eyelid, and then ascends
to innervate the skin of the forehead and the scalp as far back as the vertex.
It is accompanied by the supraorbital branch of the ophthalmic artery.
(2) The supratrochlear
nerve emerges about one fingerbreadth from the median plane and supplies
the medial part of the upper eyelid and a small area of the forehead above the
root of the nose.
(3) The infratrochlear
nerve emerges from the orbit above the
112 HEAD:
Face medial palpebral ligament and supplies a small area of skin around the
upper eyelid and the adjacent part of the nose.
(4) The external
nasal nerve emerges on the face at the lower border of the nasal bone and
supplies the skin of the nose as far down as its tip.
(5) The lacrimal
nerve supplies the lateral part of the upper eyelid and the corresponding
part of the conjunctiva. At times a nasociliary division of the ophthalmic
nerve is described; it has been referred to in this text as the infratrochlear
or
the external nasal nerve. The maxillary, or second division of the
trigeminal nerve, has the following branches:
(1) The infra-orbital
nerve, a direct continuation of the maxillary, emerges from the
infra-orbital
foramen, passes under cover of the levator labii superioris and is accompanied
by a small artery. It divides into terminal branches: the palpebral for the
lower
lid, nasal for the posterior part of the nose, labial for the upper lip, and
buccal
for
the cheek.
(2) The zygomaticojacial
nerve appears through the foramen of the same name as a twig and supplies
the skin over the bony prominence of the cheek.
(3) The zygomaticotemporal
nerve passes through the foramen of the same name,
pierces
the temporal fascia near the zygomatic bone and supplies the skin of the
anterior
part of the temple.
The mandibular,
or third division of the trigeminal nerve, has 3 branches which reach the
skin:
(1) The mental
nerve emerges through the mental foramen and is situated deep to the
depressor anguli oris; it sends its terminal branches to the lower lip, the
chin and the skin over the body of the mandible.
(2) The
buccal nerve appears at the anterior border of the ramus of the jaw below the
level
of the parotid duct and travels almost to the angle of the mouth. It supplies
the
skin
over the cheek, and the branches that pierce the buccinator supply the mucous
membrane
of the cheek.
(3) The auriculotemporal
nerve is accompanied by the superficial temporal artery and passes under
cover of the parotid gland. As its name implies, it supplies cutaneous branches
to the auricle and the temporal region, but it also supplies the modified skin
which lines the external auditory meatus and cover the outer surface of the
tympanic membrane. The terminal branches on the scalp may reach as high as the
vertex.
The
mandibular nerve supplies the skin over the lower jaw but extends onto the
external ear and upward to the side of the head. The branches of the 5th nerve
which appear on the face communicate with branches of the 7th. For this reason
a lesion in the territory of the 5th may cause a reflex spasm involving the
facial muscles and producing a so-called facial tic. These conditions are
treated best by removing the irritating cause, but they may require temporary
interruption of the reflex arc by crushing the 7th nerve where it leaves the
stylomastoid foramen. Trigeminal neuralgia is manifested by acute pain in the
parts supplied by branches of the 5th nerve and may be due to carious teeth,
sinus disease or irritative lesions within the cranium. In some cases of
intractable neuralgia where all sources of possible peripheral irritation have
been removed, it may be necessary either to resect nerves where they leave
their bony canals or inject them with alcohol. If a lesion
completely involves the 5th nerve, an extensive anesthesia of the same side of
the face results which extends exactly to the midline. The muscles of
mastication of the same side are also paralyzed, but the buccinator, which is
supplied by the 7th nerve, remains intact. If only the 1st and the
2nd divisions of the 5th nerve are severed, the loss is entirely sensory, but
if the 3rd division is cut, there is a sensory loss as well as a paralysis of
mastication.
The facial
nerve, supplying motor branches to the muscles of expression, also sends
fibers to the stapedius, the stylohyoid, the posterior belly of the digastric,
the scalp muscles, the auricle and the face, including the buccinator and the
platysma; it provides secretory fibers to the salivary glands and sensory
(taste) fibers to the tongue and the palate. Developmentally, the 7th is the
nerve of the hyoid arch; therefore, it supplies all the muscles derived from it.
It leaves the skull at the stylomastoid foramen, turns forward, laterally and
slightly downward, then enters the parotid isthmus and passes be- tween fhe
superior and the deep lobes of the gland. It lies superficial to the external
carotid artery and the posterior facial vein and may be injured in operations
in this region or on the parotid gland. The terminal branches of the nerve
appear at the margins of the parotid and spread like the rays of an open fan or
a goose's foot (pes anserinus). The 5 terminal branches are: (1) The temporal branch appears at the upper border of
the gland and runs upward and forward to supply the facial muscles above the
zygoma and the frontalis muscle. (2) The zygomatic branch emerges from
the anterior border of the parotid abovethe parotid duct and supplies the
muscles below the eye. (3) The buccal branch passes below the duct and
supplies the buccinatorand the orbicularis oris; it communicates with the
buccal branch from the mandibular division of the trigeminal nerve. (4) The mandibular
branch emerges still lower and supplies the muscles of the chin and the
lower lip. (5) The cervical branch appears at the lower end of the
parotid, passes within a fingerbreadth of the angle of the jaw between the platysma
and the deep fascia, supplies the platysma and then sends twigs up to the
muscles of the lower lip. Coleman believes that there is a complicated and
intricate intermingling of the various branches of the facial nerve so that the
fibers meant for one group find their way toanother.
CLINICAL AND
SURGICAL CONSIDERATIONS
Trigeminal
Neuralgia. Trigeminal
neuralgia (tic douloureux, facial neuralgia) is a neuralgia
of the 5th cranial nerve which is associated with severe pain along one or more
of its divisions. Some surgical measures have been adopted to alleviate or cure
the condition,among them alcohol injection into the
nerve or into the gasserian ganglion and, ifthis fails, division of its sensory
route. Most authorities have abandoned operations on theganglion, since good
results are obtained by section of the sensory root. The first division of this
nerve is rarely at fault, but involvements of the 2nd and the 3rd divisions are
frequent.
Injection of
the Maxillary Nerve. Injectionof
the maxillary nerve should be done where the nerve emerges from the foramen
rotunduminto the pterygopalatine fossa. Two points should be marked the first
is marked in the angle between the anterior border of the coronoid process and
thelower border of the zygomatic arch; the second is marked in the angle
between the upper border of the zygoma and its frontal process. Then these two
lines are joined by a straight line, and a needle is inserted at the first
point and passed upward and inward at an angle of 45° with the horizontal. The
needle is kept in the direction of the line constructed and passes behind the
mandible to enter the pterygopalatine fossa. It will strike the bone which
forms the margin of the foramen rotundumabout 2 or
Injection of the Mandibular Nerve This
is done at the foramen ovale. The needle is inserted at the center of and under
the zygomatic arch and then directed slightly forward. It will strike the outer
lamella of the pterygoid process. Then the needle is withdrawn slightly and
directed backward, where it will enter the foramen ovale. Injection of the
Gasserian (Semilunar) Ganglion This is made through the foramen ovale and
is done in the following way: a mark is made on the skin of the face about
FIG.
Injection of the maxillary and the mandibular nerves: (A) direction of needle
for the injection of the maxillary and the mandibular nerves (B) injection of
the mandibular nerve.
MUSCLES
The facial
muscles are placed around the orifices of the eye, the ear, the nose and the
mouth and act as sphincters or dilators
FIG.
Injection of the gasserian ganglion.
All are
innervated by the 7th (facial) nerve. It is extremely difficult to memorize
this confusing group; hence, it is best to locate two landmarks around
which the muscles are arranged. The two landmarks are the two orbicularis
muscles, namely, the orbicularis oculi and the orbicularis oris. Two muscles
are associated with the nose, two muscles with the zygoma, two are
levators of the lip, two are at the angle of the mouth, two are
placed at the lower lip, and the two remaining muscles are associated
with the chin and the cheek.
Orbicularis Oculi. This muscle has 3
parts, namely, the orbital, the palpebral and the lacrimal. The orbital
portion passes in circular form from the medial palpebral ligament and the
adjacent part of the frontal bone across the forehead, the temple, the cheek
and back to the medial ligament where it started. Since these fibers have no
lateral attachments, they draw the lids medially. They are responsible for the
"crow's feet" usually seen at the lateral angles of the eye. The palpebral
portion, arising from the medial palpebral ligament, which is a short fibrous
cord stretched horizontally from the medial commissure of the eyelids to the
adjoining part of the maxilla, curves laterally in both eyelids. The fibers of
this part are inserted into the lateral palpebral raphe and are located within
the lid proper and in front of the palpebral fascia.
FIG. Division
of the sensory root of the trigeminal nerve.
They usually
act involuntarily and close the lids in sleeping and in blinking. The lacrimal
part (Homer's muscle, tensor tarsi) is made up of fibers which pass
medially behind the tear sac and attach to the posterior lacrimal crest,
keeping the lids closely applied to the eyeballs. This part of the orbicularis
oculi can also contract independently of the other two portions, and by this
independent action wrinkles the skin around the eye, giving partial protection
from light or wind. Those fibers which insert into the skin of the eyebrow draw
it down as in frowning and also draw the eyebrows closer together, producing
one or more vertical furrows in the middle of the forehead. Orbicularis
Oris. This sphincter muscle of the mouth forms the greater part of the
substance of the lips. Its fibers encircle the oral aperture and extend upward
to the nose and downward to the groove which is situated between the lower lip
and the chin. Many of its fibers are derived directly from the buccinator;
others from the depressors and the elevators of the angles of the mouth. This
complex arrangement makes possible the varied movements of the lips, such as,
pressing, closing, pursing, protruding, inverting and twisting. Muscles
Associated With the Nose. These two muscles are the procerus and the
compressor nares. The procerus muscles unite. They arise from the fascia
covering the lower parts of the nasal bones, broaden and insert into the skin
between and above the eyebrow. Their fibers interlace with the frontal bellies
of the occipitofrontalis.
FIG. The
muscles of the face.
FIG.The
parotid gland: (A) superficial relations, (B) the most common pattern formed by
the fine branches of the facial nerve.
By their
contraction they draw down on the skin of the root of the nose and produce
transverse wrinkling. The compressor nares muscle originates from the
side of the bony aperture of the nose and spreads out as a fan-shaped muscle
just above it. It joins its fellow of the other side, thus forming a sling
across the bridge of the nose. It compresses the nostril, and its action is
especially well demonstrated in the crying of infants. (Two other muscles, the
dilator naris and the depressor septi nasi, are also found in this area but are
small and clinically unimportant.)
Muscles
Associated With the Zygomatic Area. These two
muscles are the zygomaticusminor and the zygomaticus major.The zygomaticus
minor arises from the zygomatic bone and is closely related to the lateral
margin of the levator labii superioris. This is a mere muscular slip and is
often absent. The zygomaticus major is both longer and thicker than the
minor and runs obliquely from the zygomatic bone to the angle of the mouth. The
major has been referred to as the "smiling muscle." Lip Elevators.
These two muscles are the levator labii superioris alaeque nasi and the
levator labii superioris. The levator labii superioris alaeque nasi is a
small muscle lying along the attachment of the nose; it divides and inserts
into the ala and the upper lip. It aids in dilation of the nostril and elevates
the upper lip. The levator labii superioris muscle is thin, fairly wide
and descends from the infraorbital margin into the upper lip. It is overlapped
by the orbicularis oculi.
Muscles
Associated With the Angle of the Mouth. These two
muscles are the levator anguli oris (caninus) and the depressor anguli oris
(triangularis). The levator anguli oris lies deep to the levator
superioris; it arises from the upper jaw below the infra-orbital foramen,
inserts partly into the skin of the angle of the mouth and blends with the
orbicularis oris. It also lies deep to the zygomatic major. The depressor
anguli oris muscle is placed superficially. It is triangular in shape, its
base corresponding to its insertion in the neighbourhood of the angle of the
mouth.
FIG. Deep
relations of the parotid gland: (A) the ramus of the mandible has been cut
across transversely, showing the superficial and deep lobes of the gland
connected by the isthmus; (B) venous pattern commonly found in the gland
substance.
Muscles
Associated With the Lower Lip. These two muscles are the
risorius and the depressor labii inferioris. The risorius lies
horizontally opposite the angle of the mouth but may be continuous with the
posterior fibers of the platysma or may arise independently from the fascia
covering the masseter muscle. Its fibers converge at the angle of the mouth,
where they are inserted into the skin. By drawing the angle of the mouth in a
lateral direction, the muscle plays a large part in the production of a smile
and has been referred to as the "grinning muscle." The depressor
labii inferioris muscle is short and wide, lies in front of the depressor
anguli and is overlapped by it. Its medial groove meets and decussates with
that of its fellow above the transverse groove on the lip, leaving a triangular
space which is filled by the mentalis.
Muscles
Associated With the Chin and the Cheek. The mentalis
muscle passes from the lower incisor downward to the skin over the chin.
When it contracts, it raises the skin over this area, thereby accentuating the
transverse fold. The buccinator muscle is situated more deeply and forms
the fleshy stratum of the cheek. Its fibers pass horizontally forward to the
angle of the mouth. The mucous membrane of the cheek and the lips lines its
inner surface. The muscle arises from the alveolar margins of both upper and
lower jaws external to the molar teeth and more posteriorly from the
pterygomandibular raphe. The uppermost and lowermost fibers pass directly into
the upper and the lower lips, respectively; but the middle fibers decussate,
the upper half running into the lower lip and the lower half into the upper
lip. At the angle of the mouth the muscle blends with the orbicularis oris. It
retracts the mouth angle and therefore is considered as the antagonist of the
orbicularis oris. Since the buccinator is supplied by the facial nerve, it is
not classified as a muscle of mastication; however, it is used during
mastication to press the cheek against the teeth and to prevent the food from
escaping into the vestibule of the mouth. It also aids in the action of blowing
and sucking. The buccopharyngeal fascia is a thin sheet that clothes the
surface of the buccinator muscle and extends
ackward to cover the constrictor muscles of the pharynx. The parotid
duct on its way to the vestibule of the mouth pierces this fascia, the
buccinator and the mucous membrane of the mouth. The buccal fat pad, also
referred to as the suctorial pad, is situated on the buccinator muscle. It is a
mass of fat, encapsulated in fascia, which lies on the muscle partly tucked in
between the buccinator and the masseter. The buccal nerves, small vessels and
the parotid duct pierce it. It thickens the cheek and helps to reduce
atmospheric pressure during sucking. It is much larger in infants than in
adults, and the rounded fullness of a baby's cheek is largely due to it.
PAROTID
REGION Although the parotid gland may be considered as a constituent of the
neck, its relations to the face are more numerous and of greater practical
importance.
PAROTID GLAND
The parotid gland is the largest of the salivary glands; it fills the parotid
space and sends a process forward over the masseter muscle. Its fibrous capsule
sends septa into the interior of the gland, dividing it into lobules and making
removal difficult at times. In this respect it differs from the submaxillary
gland, which is loosely enveloped and easily shelled out. In front of the
styloid process and from the medial surface of the gland is a pharyngeal
prolongation which is closely related to the wall of the pharynx and to the
great vessels in the parapharyngeal space. The fascial septum separating this
aspect of the gland from the carotid sheath may be broken through by pathologic
erosions or malignant tumors as well as sharp instruments. The parotid gland
has the following relationships: superficially, it is covered by skin, superficial
fascia lymph glands, fibrous capsule and branches of the great auricular nerve.
The upper border is in contact with the external auditory meatus and the
temporomandibular joint; abscesses of the gland
may perforate into either of these structures. The anterior border is
grooved by the masseter, the ramus of the mandible and the internal pterygoid
muscle. The posterior border is in contact with the mastoid process and
the sternocleidomastoid muscle. The lower border overlaps the internal
and the external carotid arteries and the internal jugular vein. The deep
surface is in contact with the digastric and the styloid muscles, the
internal and the external carotid arteries, and the 9th, the 10th, the 11th and
the 12th cranial nerves. Confusion still exists concerning the
relationship between the facial nerve and the parotid gland In 1912 Gregoire
described a superficial and a deep lobe of the parotid gland joined by an
isthmus that was situated above the facial nerve. In 1917 McWhorter also
described two lobes, but, in his opinion, the isthmus lay between the main
divisions of the nerve. In 1945 McCormack, Cauldwell and Anson confirmed this
work. In 1948 McKenzie stated that there were several isthmuses connecting the
superficial and the deep lobes of the parotid gland. The branches of the facial
nerve passed between these isthmuses so that the superficial and the deep lobes
of thegland could be joined at various locations.
FIG. Some of
the variations between the parotid gland and the facial nerve. A. The two
parotid lobes are united by an isthmus. B. The lobes are united above. C. A
combination of a and b D. No division into superficial and deep lobes. The
nerve courses through the "one-lobed" parotid gland.
It is
difficult to determine which of these views is correct, and the surgeon working
in this area will have to keep the various patterns in mind as he performs
surgery on the parotid gland. The socia parotidis is an accessory part
of the parotid gland which lies immediately above its duct and on the masseter
muscle. The fibrous capsule of the parotid is derived from the investing
layer of deep cervical fascia which splits at the lower pole of the gland to
ensheath it. The deeper of these two layers passes under the gland and attaches
to the base of the skull; the superficial layer passes anterior to the masseter
muscle and attaches to the lower border of the zygomatic arch. This layer has
been referred to as the parotideomasseteric fascia and accounts for the intense
pain caused by inflammatory swellings of the gland. That part of the fascia
which connects the styloid process to the angle of the mandible has been called
the stylomandibular ligament and separates the parotid and the submaxillary
glands.
Nerve and Blood Supply. The uriculotemporal nerve is a sensory
branch of the mandibular division of the 5th, which supplies the skin in front
of the ear. Its course is as follows: ascending upward through the temporal
region to the vertex of the skull, the nerve emerges from the upper border of
the parotid, crosses the root of the zygoma between the external ear and the
condyle of the jaw and divides into its temporal branches. It may be compressed
by tumors or swellings in the parotid gland and produce exquisite pain
radiating over the temple as high as the vertex. The 7th or facial
nerve, emerging from the stylomastoid foramen, divides into its two main
branches, which embrace the isthmus of the parotid gland. From here these
branches redivide and radiate from the border of the gland in the form of a goose's
foot (pes anserinus). This has been discussed elsewhere. Although veins are
variable, they follow a fairly constant course in the substance of the parotid
gland. The posterior facial vein aids in the formation of two other
veins—the external jugular and the common facial. At its lower end and while in
the parotid, the posterior facial divides into an anterior and a posterior
branch. The anterior branch joins the anterior facial vein to form the common
facial, and the posterior joins the posterior auricular to form the external
jugular vein. The external carotid artery ascends from under cover of
the digastric and the stylohyoid muscles and comes into relationship with the
posteromedial surface of the parotid. Here it gives rise to a-posterior
auricular artery and then enters the gland, passing from the posteromedial to
its anteromedial surface. At the back of the neck of the mandible it divides
into internal maxillary and superficial temporal branches. The superficial
temporal artery arises under cover of the parotid gland, emerges at its
upper border, accompanied by a corresponding vein and the auriculotemporal
nerve. It ascends across the root of the zygoma, where its pulsations may be
felt readily; it continues upward on the temporal fascia and divides into
anterior and posterior branches, which supply the scalp. In addition to many
small branches which supply the parotid gland, the auricle and the facial
muscles, the superficial temporal supplies a transverse facial artery which
runs forward on the masseter muscle, emerges at the anterior border of the
gland and continues parallel with and above the parotid duct. The lymph
glands of the parotid region may be divided into two groups: a superficial,
which is superficial to the parotid sheath and constitutes the preauricular
group draining the temporal and the frontal regions of the scalp, the outer
portion of the eyelid and the outer aspect of the ear. A deeper group makes up
the parotid group, which is scattered through the gland substance and drains the
upper and posterior parts of the nasopharynx, the soft palate and the middle
ear. These relationships are important because swellings of the parotid gland
may be confused with enlarged and infected lymph glands in this region.
Parotid
(Stensen's) Duct. The duct of the parotid gland begins at
the anterior part, passes forward on the masseter muscle about one
fingerbreadth below the zygoma and is accompanied by the transverse facial
artery above and the buccal branch of the facial nerve below. It bends abruptly
around the anterior border of the masseter, pierces the substance of the
buccinator muscle, runs obliquely forward between the buccinator and the mucous
membrane of the mouth and opens on a papilla opposite the upper 2nd molar
tooth. It may be felt best when the jaws are clenched, because it then can be
rolled against the tense masseter muscle. The duct is about 2 ½ inches
long and 1/8 inch in diameter, its orifice being its narrowest part. The bend
the duct makes
FIG.
Parotidectomy: (A) Incision which also may be utilized for preliminary ligation
of the external carotid artery. (B) Mobilization of the superficial lobe. The
numbers indicate the order in which this dissection takes place. (C) Division
of the isthmus. The operation may end at this stage if only the superficial
lobe is involved, or it may be continued by putting traction on the isthmus and
removing the deep lobe. The branches of the facial nerve are visualized and
protected.
around the anterior border of the masseter may be
so sharp that the buccal segment remains at right angles to the masseteric
part. This should be kept in mind if a probe is passed along the duct from the
mouth. Its course can be marked by the middle third of a line which joins the
lobule of the ear to the midpoint between the red margin of the upper lip and
the ala of the nose.
SURGICAL
CONSIDERATIONS
PAROTIDECTOMY
Most authorities believe that mixed tumors of the parotid gland are potentially
malignant and, therefore, should be subjected to complete extirpation. In total
parotidectomy, a long incision is made in front of the ear and as close as
possible to the cartilage. The inferior end of this incision turns around the
lobule, extends to the mastoid process and then downward along the anterior
border of the sternocleidomastoid muscle. Bailey is of the opinion that one of
the first steps should be the ligation of the external carotid artery, which
makes the operation easier and safer. The anterior skin flap is reflected
forward to the mandible. The submaxillary salivary gland within its capsule is
utilized as a landmark, and the posterior belly of the digastric is identified.
Mobilization of the superficial parotid lobe is the next step and is
accomplished best by commencing at the anterior extremity of its lower border.
Sistrunk has advised isolating the inframandibular branch of the facial nerve
first as it passes along the angle of the jaw, but many surgeons have found
difficulty in locating the nerve before the gland has been properly freed. The
anterior extremity of the lower border is considered a safe area and is an
excellent place to commence dissection. After freeing this corner, a new
dissection is started at the extreme posterior end of the upper border of the
gland. The ear is retracted backward, and a cleavage plane is found which
allows the gland to be dissected upward and forward. In this location the
temporal artery is found, but if the external carotid has been ligated, the
temporal can be dissected up with the parotid gland or left in situ, whichever
is easier. The dissection continues along the upper border, and the gland is
lifted from the zygomatic arch. At this stage a sharp lookout is kept for the
uppermost part of the pes anserinus. It is important to preserve the upper
branches that go to the orbital region. These lie on the masseter muscle, and
once the correct cleavage plane is found, there is no great difficulty, since
the nerves have a tendency to adhere to the muscle rather than the gland. As
the dissection continues along the anterior border, Stensen's duct and at times
the socia parotidis are freed from the masseter. In the middle region the
mid-portions of the pes are seen and
freed as far as possible.The antero-inferior border of the gland which was
mobilized as the first step is now grasped and retracted upward. Dissection
then proceeds toward the mastoid process, using the digastric muscle as a
guide. At this step the main trunk of the facial nerve usuallycan be
identified. With this under vision and the gland mobilized on all sides, the
isthmus and its limitations can be made out by vision or palpation. Then the
free superficial lobe is retracted forward, and the isthmus is divided from
behind forward. This having been done, the facial nerve and its divisions will
usually become apparent. Stensen's duct is divided, if this has not been done
already. The facial nerve can be held aside by fine retractors or ligatures
passed beneath it, and the deep lobe is removed by separating it from the great
vessels of the neck and the pharyngeal wall. Sometimes bleeding occurs from the
large tributaries of the jugular vein during this stage and it may become
necessary to ligate the jugular. The surgeon must remember that this is only
one of many technics described. The various anatomic descriptions of this
region resulted in different surgical approaches. Eddey has presented an
operation in which he described three isthmuses of the parotid gland, stating
that the facial nerve is completely surrounded by glandular tissue. Riessner
uses the so-called "upper branch" of the facial nerve as a safe guide
for parotid gland removal. Many other technics can be studied by anyone
interested in the surgery of this area.
PAROTID ABSCESS A parotid abscess may be drained
through an incision (Blair) which commences about
FIG. The 6
muscles of mastication. (A) Viewed from left side; the zygomatic arch and part
of the mandible have been removed. The temporal muscle has been cut for the purpose
of exposing the pterygoid muscles. (B) Viewed from below
FIG. The
internal maxillary artery. The vessel is divided into 3 parts by the external
pterygoid muscle. Part I is known as the mandibular portion; Part II, the
pterygoid; and Part III, the pterygopalatine portion. The branches of each part
are numbered and
represented.
VESSELS
AND NERVES
Internal
Maxillary Artery. This artery arises from the external
carotid opposite the neck of the mandible and under cover of the parotid gland.
It passes forward deep to the neck of the bone and superficial to the
sphenomandibular ligament. Between the mandible and the sphenomandibular
ligament it is accompanied by its vein and lies superficial to the inferior
alveolar (dental) nerve. It goes upward and forward superficial to the external
pterygoid between it and the temporal muscle, or deep to the external
pterygoid, between it and branches of the mandibular division of the 5th nerve.
It then passes medially between the two heads of the pterygoid and through the
pterygomaxillary fissure into the pterygopalatine fossa, to end in its numerous
terminal branches. The external pterygoid muscle divides the maxillary artery
into three parts. The first is known as the mandibular portion; it lies between
the neck of the mandible and the sphenomandibular ligament, taking a horizontal
course forward nearly parallel with and a little below the auriculotemporal
nerve. In this location it is imbedded in the parotid gland and usually crosses
in front of the inferior alveolar nerve. The second part is called the
pterygoid portion, and here the artery may lie lateral or medial to the
external pterygoid muscle. This part of the artery usually runs obliquely
forward and upward under cover of the ramus of the mandible and passes on the
superficial surface of the muscle. The vessel then passes between the two heads
of origin of this muscle and enters the pterygopalatine fossa. Part three of
the vessel, the pterygopalatine portion, lies in the pterygopalatine fossa in
relation to the sphenopalatine ganglion. The branches which arise from the
first part of the artery are associated with foramina; those which come from
the second part are associated with muscles, and the branches of the third part
are again associated with foramina. The branches of the first part of the
internal maxillary artery are: 1. The deep auricular artery, which
passes to the external auditory meatus. 2. The anterior tympanic, which
enters the pterotympanic fissure to the middle ear. 3. The middle meningeal,
which arises from the upper border of the maxillary bone and runs upward
and deep to the external pterygoid muscle. As it ascends it is embraced by the
two heads of the auriculotemporal nerve; it enters the middle cranial fossa
through the foramen spinosum and upward and forward on the squamous temporal
and great wing of the sphenoid bone toward the antero-inferior angle of the
parietal bone, where it divides into anterior and posterior branches. The
anterior branch travels upward across the great wing of the sphenoid toward the
pterion and then on the parietal bone behind the coronal suture near the motor
cortex. The posterior branch passes upward and backward on the squamous
temporal to the middle of the lower border of the parietal bone and then breaks
up into its terminal branches. 4. The accessory meningeal, also referred
to as the small meningeal artery, has a similar course and may be a
branch of the above-mentioned vessel; it enters the middle cranial fossa
through the foramen ovale and supplies the dura mater and the trigeminal
ganglion. 5. The inferior alveolar (dental) artery passes downward
behind the inferior alveolar nerve and between the sphenomandibular ligament
and the mandible. It supplies a mylohyoid branch and then enters the mandibular
foramen to supply the teeth and the lower jaw. Its terminal branch appears on
the face accompanied by the mental nerve. There are 4 branches of the second
portion of the internal maxillary artery: 1. The masseteric artery passes
laterally through the mandibular notch to the masseter muscle and also supplies
the mandibular joint. 2. The deep temporal has 2 branches, anterior and
posterior, which ascend between the temporalis muscle and the pericranium; they
supply the muscle and anastomose with the middle temporal artery. 3. The pterygoid
arteries are irregular in number and origin and supply the pterygoid
muscles. 4. The buccinator (buccal) artery travels forward with the
buccal nerve between the internal pterygoid and the jaw to supply the
buccinator muscle, the skin and the mucous membrane of the cheek. The 6
branches of the third portion of the internal maxillary artery are: 1. The posterosuperior
alveolar, which descends over the posterior surface of the maxilla, sends
branches to the gums, the buccinator muscle, through the bone to the molars,
the premolars and the maxillary sinus. 2. The infra-orbital artery, really
a continuation of the parent trunk, is accompanied by the maxillary nerve
through the infraorbital canal, appearing on the face beneath the levator labii
superioris. In the canal it sends branches to the orbit and an anterior dental
branch which accompanies the nerve and supplies the front teeth. On the face it
supplies the lacrimal sac and the medial angle of the orbit.
FIG. The lingual
and the inferior alveolar (dental) nerves.
3. The greater
palatine artery passes through the greater palatine canal with the nerve of
the same name, then along the hard palate in a groove about 1/2 inch
from the teeth, and finally through the lateral incisive foramen to the nose.
4. The pharyngeal artery is very small and passes backward through the
pharyngeal canal accompanied by the pharyngeal nerve. It is distributed to the
upper part of the pharynx and the auditory tube. 5. The artery of the pterygoid
canal (Vidian) passes backward along the pterygoid canal with its
corresponding nerve. It is distributed to the upper part of the pharynx and to
the auditory tube, sending a small branch into the tympanic cavity which
anastomoses with the other tympanic artery. 6. The sphenopalatine artery enters
the nasal cavity through the sphenopalatine foramen and supplies the mucous
membrane of the nasal cavity, the adjacent sinuses and the pharynx. At the back
part of the superior meatus it supplies posterior lateral nasal branches which
spread forward over the conchae and the meatus, anastomosing with the ethmoidal
arteries and nasal branches of the descending palatine artery. It ends on the
nasal septum as posterior septal branches which anastomose with the ethmoidal
arteries and the septal branches of the superior labial. One branch descends in
a groove on thevomer to the incisive canal and anastomoses with the descending
palatine artery.
Pterygoid
Venous Plexus. This rich network of veins is located around the
lateral pterygoid muscle; veins corresponding to the maxillary artery empty
into it. From its posterior end a maxillary vein passes backward to unite with
the superficial temporal, forming the posterior facial vein. The plexus makes
the following communications: with the cavernous sinus through the foramen
ovale; with the anterior facial through the deep facial vein; with the inferior
ophthalmic veins through the inferior orbital fissure.
Mandibular
Division of the Trigeminal Nerve. In the parotid region this
plays an important role. It leaves the skull through the foramen ovale in the
greater wing of the sphenoid bone and differs from the other two divisions in
that it is a mixed nerve. The sensory part arises from the gasserian ganglion,
and the motor part is the motor root of the 5th nerve. The two roots pass
through the foramen ovale and almost immediately unite into one trunk which is
covered by the external pterygoid muscle. It lies on the surface of the tensor
palati (veli palatina) muscle, which separates the nerve from the auditory
(eustachian) tube and the nasopharynx. The middle meningeal artery lies lateral
to and a little behind it. The trunk divides into anterior and posterior
divisions. The undivided trunk gives off a recurrent nerve and the nerve to the
internal pterygoid muscle. The recurrent nerve (nervus spinosus) passes back
into the foramen spinosum and supplies the dura and the mastoid air cells. The
nerve to the internal pterygoid muscle is self-explanatory. From the anterior
division, mainly muscular, are derived the deep temporal, the masseteric, the
external pterygoid and the long buccal branches. From the posterior division,
mainly sensory,are derived the auriculotemporal, the inferior dental (alveolar)
and the lingual nerves. Although the anterior division of this nerve gives off
muscular branches to the temporal, the masseter and the external pterygoid
muscles, the long buccal nerve is essentially sensory; it passes down between
the two eads of the external pterygoid
muscle, pierces the anterior part of the temporal muscle, traverses the
suctorial fat pad, and then branches outward to the skin of the face and inward
to the mucous membrane of the cheek.
Auriculotemporal
Nerve. This nerve has been discussed elsewhere. It is a
sensory branch of the mandibular nerve which forms an anastomosis with the
facial nerve and otic ganglion. It emerges from the upper border of the parotid
and crosses the root of the zygoma between the external ear and the condyle of
the jaw, where it divides into its temporal branches. This nerve is sometimes
resected in persistent neuralgias and is easily found where it crosses the
zygoma, lying between the ear and the temporal artery. By means of its
communication with the otic ganglion, secretory fibers result;these supply the
parotid gland; hence, the rationale for division of it in an attempt to close a
parotid fistula. Auricular branches of this nerve pass to the upper ear and the
external auditory meatus. Referred pain from these branches may be so severe that
the ear drum may be opened unnecessarily when one of the molar teeth is at
fault.
Lingual
Nerve. This nerve passes downward deep to the external and on
the surface of the internal pterygoid muscle. In this part of its course it is
in front of the inferior alveolar nerve and is joined by the chorda tympani
(7th nerve), which contains taste fibers that are carried by the lingual to the
anterior two thirds of the tongue. As the nerve continues downward and forward
it lies between the mandible and the internal pterygoid, and farther forward is
under cover of the mucous membrane of the mouth on the superior constrictor and
the stvloglossus muscles. It passes forward between the mylohyoid and the
hyoglossus and arrives between the sublingual gland and the genioglossus
muscle, where it crosses the submandibular duct and supplies the gums and the
anterior two thirds of the tongue. One should not be confused between taste and
sensation if one recalls that the lingual nerve supplies the anterior two
thirds of the tongue with its sensory fibers, but this nerve carries fibers
from the facial nerve by way of the chorda tympani, which supply taste fibers
to the same region of the tongue. Resection of the lingual nerve is at times
necessary for the relief of intense pain which is associated with carcinoma of
the tongue.
Inferior
Alveolar (Dental) Nerve. This nerve passes downward deep to
the external pterygoid muscle but superficial to the sphenomandibular ligament
and is accompanied by the dental vessels. Immediately before entering the
mandibular foramen it gives off the nerve to the mylohyoid muscle; this
descends in a groove on the deep surface of the mandible in company with the
mylohyoid vessels.
FIG. The
temporomandibular joint: (A) lateral view, right side; (B) exposure of the
joint and the articular disk, following removal of the temporomandibular
ligament and part of the condyle of the mandible; (C) medial view, showing the
stylomandibular and the sphenomandibular ligaments.
This nerve
reaches the posterior edge of the mylohyoid, passes superficial to that muscle
and ends by supplying the mylohyoid and the anterior belly of the digastric. In
the inferior dental canal it sends branches to the roots of the lower teeth and
gums. The nerve finally emerges through the mental foramen as the mental nerve.
TEMPOROMANDIBULAR
JOINT The temporomandibular (temporomaxillary, mandibular) is a synovial joint
that is formed by the head of the mandible with the articular fossa and the
eminence of the temporal bone. The articulating surfaces are completely
separated by an articular disk which divides the joint cavity into an
upper and a lower chamber. The joint is surrounded by a lax capsule which
envelops the bony articular surface and furnishes attachment to the interposed
cartilage. The laxity of this capsule enables free joint movements. Over its
lateral aspect the capsule is markedly thickened and strengthened by the temporomandibular
ligament (external lateral ligament), which stretches from the zygoma and
the tubercle at its root to the lateral and the posterior surfaces of the neck
of the mandible. The ligament is covered by the upper part of the parotid gland
and is in relation to the superficial temporal vessels. The articular disk is
attached around its circumference to the capsular ligament. However, there is
an exception to this attachment, since the disk receives part of the insertion
of the external pterygoid muscle in front. The lower disk surface is concave to
fit into the head of the mandible, but its upper surface undulates to fit the
fossa and the eminence. The disk can become loose or detached and, as it slips
back and forth, may produce an audible click (clicking jaw). At times it may
become detached at one end and is then apt to double on itself, in which event
it becomes impacted between the joint surfaces and causes locking; the symptoms
may become so discomforting and embarrassing that removal of the disk is
necessary. Two accessory ligaments described as bands and giving additional
ligamentous support to the joint are the sphenomandibular and the
stylomandibular. The sphenomandibular ligament (internal lateral ligament) lies
on a deeper plane than the joint, distinct from the medial part of the
articulation, and is a thin and fairly long band stretching from the spine of
the sphenoid bone to the edge and the margins of the mandibular foramen
Medially, its upper part is separated by fat from the wall of the nasopharynx,
and its lower part lies on the internal pterygoid muscle. Laterally, it is
related to the mandibular joint, and the mandible is separated from the
ligaments, from above downward, by the auriculotemporal nerve, the external
pterygoid muscle, the maxillary vessels and the inferior dental vessels and
nerves. Although these structures separate the ligament from the joint, the
chorda tympani nerve lies deep to the ligament. The stylomandibular ligament
is a thickened part of the cervical fascia that covers the deep surface of
the parotid gland. It extends from the styloid process to the posterior border
and angle of the mandible and separates the parotid from the submandibular
gland. The synovial membrane is in two separate parts, since it has two
separate cavities to line. The upper synovial cavity is the more extensive
because of the greater size of the articular fossa of the temporal bone. The
membrane, although reflected onto the articular disk, disappears from this part
in the adult. The construction of the temporomandibular joint permits a wide
range of movements. Elevation is produced by the masseter, the internal
pterygoid and the temporalis muscles; depression by the digastric, the
mylohyoid, the geniohyoid and the platysma, protrusion by the pterygoids, the
anterior part of the temporalis and fibers of the masseter; retraction by the
posterior fibers of the temporalis and the deeper fibers of the masseter.
Grinding movements are produced by the pterygoids of opposite sides acting
alternately.
FIG. Anterior
dislocation of the mandible. The condyle has been drawn over the articular eminence
into the zygomatic fossa by the contraction of the external pterygoid. Then the
mandible is drawn upward and fixed in place by masseter, internal pterygoid and
temporalis muscles.
The
construction of the joint permits a forward dislocation, either unilateral or
bilateral, which can occur when the mouth is widely opened. Such dislocations
have occurred during a blow struck on the lower front teeth, or during
laughing, yawning, vomiting and also in the dentist's chair. When the mouth is
opened widely, the condyles and the interarticular fibrocartilage glide
forward. Normally, the condyles should not reach as far as the summit of the
articular eminence, but when the mouth is opened widely all parts of the
capsule except the anterior are made tense, and if at this time the external
pterygoid muscle contracts vigorously, the condyle is drawn over the articular
eminence onto the zygomatic fossa and the interarticular cartilage remains
behind. As soon as it reaches its new position, it is drawn up immediately by
FIG. Sagittal
section through the upper lip. The 5 layers which constitute each lip are
shown.
FIG. Alveolar
abscesses and their possible paths of invasion. In the upper jaw, the infection
may spread to the external bony plate, into the mouth, the nasal cavity or the
maxillary sinus. In the lower jaw, abscesses may burrow between periosteum and
soft tissue, or between periosteum and bone, and then discharge on the neck,
between the jaw and the chin; pus may also find its way to the floor of the
mouth, resulting in Ludwig's angina.
the internal
pterygoid, the temporal and the masseter muscles and is thereby spastically
fixed in place.
FIG. The
venous drainage of the teeth and possible paths of extension of a thrombophlebitis.
The veins of the upper jaw drain in two directions: the anterior drains into
the anterior facial vein, and the posterior into the pterygoid plexus.
Following a tooth extraction, these infections may travel to the pterygoid or
the pharyngeal plexus. Pterygoid plexus infections can extend to the inferior
ophthalmic veins or through the foramina lacerum and ovale. In cavernous sinus
thrombosis following anterior teeth infections, the thrombophlebitis usually
spreads from the anterior facial vein through the orbit via the ophthalmic
veins, usually the superior.
FIG.
Infections about the face and the mouth: (A) the 3 muscular fascial spaces, (B)
approach to abscesses above and below the geniohyoid muscle.
PRACTICAL
CONSIDERATIONS
THREE
MUSCULAR FASCIAL SPACES AND ONE VASCULAR VISCERAL SPACE
Coller and
Yglesias have emphasized the fact that the fasciae in this region are attached
to periosteum, enclose facial muscles and form closed spaces. In this way the spaces
are separated from cervical fascial spaces, and infections do not spread into
the neck but remain limited. However, the fasciae which surround the viscera
and the vessels are continuous between the face and neck so that infections may
travel from one to the other. These authors have described three muscular
fascial spaces and one vascular visceral space.
Space of the
Body of the Mandible. This fascial space exists between the
superficial and the deep divisions of the middle muscular fascia. It has an
important bearing on infections of this bone and, because of the fascial
attachment, osteomyelitis of the body of the mandible is prevented from
spreading either superficially or deep. An infection in this location may do
one of three things: discharge into the mouth, spread to the masticator space,
or remain localized. The space is drained through the mouth by means of an
incision that goes through the gingival mucous membrane of the vestibule or by
an incision through the skin along the inferior border of the body of the bone.
Masticator
Space. The second space is occupied by the ramus of the
mandible. It is bounded externally by the masseter, internally by the
pterygoids and superiorly by the temporal muscle. Infections in this space may
travel upward either to the so-called superficial or to deep temporal spaces.
The temporal spaces may be drained by incisions that are carried through the
skin, the subcutaneous tissue and the temporal fascia. If the malar bone or the
zygoma are involved, resection of either may be necessary.
Parotid
Space. This is the third fascial space of the face. It is
occupied by the parotid gland. Drainage of this space can be accomplished by an
incision that is made in front of the ear and passes downward behind and below
the jaw. The external surface of the parotid is thus exposed without injury to
the facial nerve if the dissection is kept external to the glandular substance.
If it is desirable to drain the space between the masseter muscle and the
superficial part of the parotid gland, a horizontal incision is made at the
level of and parallel with the superior border of the mandible.
Visceral
Vascular Fascial Space. This is the lateral pharyngeal space.
It is bounded anteriorly by the medial wall of the masticator space, laterally
by the parotid space, posteriorly by the carotid sheath and medially by the
submaxillary gland. Since this is not one of the enclosed facial fascial
spaces, infection may travel and involve the internal carotid artery, producing
severe hemorrhage, or it can produce septic thrombosis of the internal jugular
vein. Drainage may be external through the parotid space or internal through
the lateral pharyngeal wall. Infection in this space can spread readily to the
viscerovascular spaces of the neck and the mediastinum.
UPPER AND
LOWER LIP INFECTIONS Infections in the upper lip should not be incised
or squeezed. Many surgeons advocate ligation of the angular vein, but this is
still a moot question. If pus is present, some advise drainage. Meningitis and
the occurrence of cavernous sinus thrombosis should always be kept in mind.
Infections in the lower lip are
less dangerous than those of the upper. Cavernous sinus thrombosis rarely
occurs from infections in this region because the veins lie at a deeper level and
are more efficiently splinted by muscle and bone. Two anatomic spaces are
formed in the floor of the mouth. The superficial space lies between the
genioglossus and the geniohyoid muscles and is divided into two compartments by
a median fascial septum. The second space lies at a deeper level and is
situated between the geniohyoid and the mylohyoid muscles. It, too, is divided
in the middle by a fascial septum. Ludwig's angina constitutes
involvement of these spaces, with elevation of the tongue and inflammation of
the mucous membrane over the involved area. If the infection is unilateral, the
tongue is pushed to the opposite side, but if bilateral, it is pushed upward
toward the roof of the mouth. The treatment of Ludwig's angina consists of
early drainage instituted in the involved space; hence, it is important to
determine whether the abscess is below or above the geniohyoid. If the abscess
is below this muscle, the region under the chin is prominent, and an incision
should be made through the skin, the subcutaneous tissue and the mylohyoid
muscle into the abscess cavity. If the swelling is diffuse, the incision should
follow the lower border of the mandible in order that both sides of the fascial
septum or both sides of this space can be dealt with properly. If the infection
is situated above the geniohyoid muscle, it usually points under the tongue and
then can be drained through the floor of the mouth, the incision passing
through the mucous membrane and the genioglossus muscle. Both sides of the fascial
septum should be explored.
FIG. The
palatine tonsil and its relations, shown in sagittal section.
FIG. The relations of the palatine tonsil to its
capsule and the surrounding structures.
PHARYNX TONSILS The term "tonsil"
usually applies to the faucial or palatine tonsils. The tonsillar region,
although anatomically located in the anterolateral pharynx and properly
belonging to it, is considered as an intermediate area between the buceal
cavity and the oral division of the pharynx. The tonsils are two masses of
lymphoid tissue placed in the fossa tonsillaris and located on the
surface at a point a little above the angle of the mandible. They lie between
the palatoglossal and the palatopharyngeal arches, above the back part of the
tongue and below the soft palate. Each tonsil has two surfaces (medial
and lateral), two borders (anterior and posterior), and two poles
(superior and inferior). The medial surface is free and can be seen
through the mouth when the tongue is depressed. It faces inward and presents
from 12 to 30 rounded or slitlike openings called the tonsillar crypts. Tiny
plugs of food, debris or pus often fill and identify these openings. This
surface is covered with mucous membrane in the form of squamous epithelium
which invades the substance and lines the crypts. The lateral is the
attached surface. It is covered by a fascia derived from the pharyngeal
aponeurosis, which is referred to as the capsule of the tonsil. This is
attached laterally by loose areolar tissue to the inner surface of the superior
constrictor of the pharynx. Lateral to the superior constrictor are the
ascending palatine, the pharyngeal and the tonsillar arteries; the medial
pterygoid muscle is situated lateral to these. One or more veins descend over
the lateral surface of the capsule. The superior constrictor separates the
tonsil from the facial artery at that point where the artery begins to arch
downward.
FIG. The
blood supply of the tonsil.
Poles. The upper
pole of the tonsil invades the lateral surface of the soft palate, and the lower
is continuous with the lingual tonsil. Borders. The anterior
border is in contact with the palatoglossus muscle, and the posterior with
the palatopharyngeus muscle. The blood supply of the tonsil is very
profuse, the main vessel being the tonsillar artery, a branch of the
facial (external maxillary). This vessel enters the tonsil from its lateral
aspect and near its lower pole. Other small vessels aid in the blood supply,
anastomosing freely with one another. They are the ascending palatine (facial),
dorsalis linguae (lingual), greater palatine (maxillary) and the ascending
pharyngeal arteries.
FIG.
Tonsillectomy.
The veins form a plexus which surrounds the
capsule, pierce the superior constrictor and end in the pharyngeal plexus,
which is a tributary of the internal jugular vein. The lymphatics leave
the gland, pierce the superior constrictor and end in the superior deep
cervical chain. One gland is situated below the posterior belly of the
digastric andthe angle of the jaw. It lies on the carotid artery in the angle
formed by the junction of the common facial with the internal jugular vein and
has been referred to as the jugulodigastric gland (tonsillar gland of Wood).
This may be enlarged not only in non-specific infections, but by the tubercle
bacillus when it gains entrance by way of the tonsil. The nerve supply to
the tonsil is derived from the glossopharyngeal nerve and the pharyngeal
plexus.
SURGICAL
CONSIDERATIONS
Tonsillectomy and Peritonsillar Abscess.
When a tonsil is removed, its capsule should remain attached to it. This
exposes the constrictor muscle and not the aponeurosis of the pharynx.
Therefore, the capsule is removed with the tonsil because it is firmly blended
with that organ. In tonsillectomy, traction on the gland pulls it forward
without dragging the pharyngeal wall and the internal carotid artery. This is
explained by the laxity of the tissue which exists between the gland and the
superior constrictor. However, in patients who have suffered repeated attacks
of quinsy, this lax tissue may be replaced by dense adhesions. Tonsillar
hemorrhage following surgery is the result of bleeding from the tonsillar
vessels proper, since the possibility of injuring the internal carotid is most
remote and the external carotid lies still farther externally. In tonsillectomy
, after proper exposure with a mouth gag and tongue depressor, a tenaculum is
applied to the palatal pole, and traction made downward and medially. This maneuver
makes visible the interval between the tonsil and its anterior pillar. A sharp
dissector enters this space along the anterior pillar and incises just beneath
the mucous membrane which covers the tonsil. Retraction of the anterior pillar
with blunt dissection will expose the bluewhite capsule. If sharp dissection is
preferred, the point of the scissors is applied toward the tonsil side, and an
attempt is made toremain in the avascular cleavage plane. The tonsil is freed
down to its lingual pole. A snare is then applied as low as possible on its
base, tightened, and the base divided. A retractor is applied to the anterior
pillar for the purpose of inspection, and pledgets of gauze or cotton are
introduced for hemostasis by pressure. If active arterial bleeding is present,
the severed artery is grasped and tied with a fine suture. In the treatment of peritonsillar
abscess, an imaginary line should be drawn from the base of the uvula to
the last molar of the same side. An incision is made at the junction of the
anterior one third with the posterior two thirds along the arcus palatinus.
This incision is spread with forceps, and the pus is allowed to flow out. Some
surgeons advocate entering the tonsillar fossa with a curved sharp-pointed
forceps. The approach between the tonsil and the anterior pillar seems to be an
easier method of draining the supratonsillar fossa.
Trigeminal Nerve.
This is the thickest of the cranial nerves and
has a wide distribution. It has a large sensory root upon which the semilunar
(gasserian) ganglion is situated, the ganglion resting in a fossa on the
superior surface of the petrous
FIG.
The trigeminal nerve and the semilunar (gasserian) ganglion. The lateral wall
of the orbit has been removed, and the maxillary sinus has been opened.
FIG.
Diagram of the trigeminal nerve and the semilunar (gasserian) ganglion.
glion on the
sensory. The nerve provides the sensory supply to the face and the anterior half
of the scalp and sends motor branches to the four muscles of mastication
(except the buccinator) and to four other muscles: tensor palati, tensor
tympani, mylohyoid and anterior belly of the digastric. There are five ganglia
on the 5th nerve: the semilunar on the nerve trunk, the ciliary on the
ophthalmic division, the sphenopalatine on the maxillary division, the otic on
the mandibular division, and the submaxillary (
Facial Nerve. This nerve is seen when
the cerebellum is removed. It is the motor nerve to the face and contains no
cutaneous branches. Leaving the brain at the lower border of the pons and
accompanying the auditory 8th nerve into the internal auditory meatus, it
passes through the temporal bone and leaves the skull through the stylomastoid
foramen. In the temporal bone it gives off the great superficial petrosal
nerve, which sends sensory fibers to the mucous membrane of the soft palate
and secretory fibers to the mucous glands; the nerve to the stapedius
muscle; and the chorda tympani, which passes through the tympanic
cavity, joins the lingual nerve and thus supplies taste and sensation fibers to
the anterior two thirds of the tongue and secretory fibers to the submaxillary
and sublingual glands. At the exit from the stylomastoid foramen the facial
nerve gives off the posterior auricular nerve and a branch which divides into
two twigs supplying the stylohyoid muscle and the posterior belly of the
digastric. The posterior auricular nerve ascends behind the ear and
supplies the posterior and the superior auricular muscles and the occipital
belly of the occipitofrontalis. Having given off its branches in the temporal
bone and at the exit from the stylomastoid foramen, the facial nerve supplies
its terminal branches to the face. Here it divides into two main divisions: a
temporofacial and a cervicofacial. A controversy exists at present as to
whether the facial nerve runs through the parotid gland or whether it passes
around the isthmus of the gland, thus being "sandwiched" between the
so-called superficial and deep lobes of the gland.
FIG.
The facial nerve. It divides into two divisions: the temporofacial and the
cervicofacial. These give rise to the 5 terminal branches which form the pes
anserinus (goose's foot).
The two
divisions break up into a nerve plexus which has been called the pes
anserinus (goose's foot). These terminal nerves forming the plexus emerge
at the anterior border of the parotid gland and radiate over the side of the
face in a fanlike manner. The temporofacial division gives rise to 2 terminal
branches: temporal and zygomatic. A temporal branch appears at
the upper border of the gland and supplies the frontalis muscle and the facial
muscles which are situated above the zygoma. The zygomatic branches are divided
into a smaller upper branch, which passes forward from the upper anterior
border of the parotid to the zygomatic bone and supplies the adjoining facial
muscle, and a lower zygomatic branch, which appears at the anterior border of
the gland and runs with the transverse facial vessels to the muscles of the
upper lip and the nose. The cervicofacial division gives rise to the buccal,
the mandibular and the cervical branches. The buccal
branch appears at the anterior border of the gland and supplies the buccinator
and the orbicularis oris muscles. The mandibular branch supplies the
lower lip and
the chin. The cervical branch appears at the lower border of the gland and
supplies the platysma and the depressors of the lower lip. Intracranial lesions
of the facial nerve are characterized by involvement of only the lower half of
the face; cranial lesions may result from middle-ear diseases or fractures of
the face or the skull. Extracranial lesions result in facial paralysis, as seen
in Bell's palsy, in which condition the involved side of the face is flat and
expressionless; the patient is unable to
whistle, blow out his cheeks, wrinkle his forehead or show his teeth. In its
course the facial nerve makes connections with the auriculotemporal and
the great auricular nerves.
PARANASAL
SINUSES The paranasal sinuses are irregular air spaces or diverticula
originating from buds of mucous membrane that sprout from the nasal cavities
and grow into the diploic layer of certain bones. Each sinus takes its name
from the bone in which it is situated: maxillary (antrum of Highmore), frontal,
ethmoid and sphenoid. These sinuses are enclosed in compact bone. They
communicate with the nasal cavities with which their mucous membranes are
continuous and are filled with air. They communicate with the nasal cavities by
means of narrow orifices that may become occluded because of congested mucous
membrane. Like the mucous lining of the nose, the membrane lining the sinuses
is covered with ciliated epithelium. The anatomy of the paranasal sinuses is
somewhat inconstant, since there is no definite constancy in their size, shape
and type. Under normal conditions during respiration there is an interchange of
air between them.
MAXILLARY
SINUS (ANTRUM OF HIGHMORE) This maxillary sinus is the largest of the paranasal
sinuses and is the first to appear. Although it begins to develop about the 4th
month of intra-uterine life, it continues to grow in the adult, acquiring its
maximum development in the 2nd or the 3rd decade. The sinus varies considerably
in size in different individuals, but the following have been given as the
average dimensions: anteroposterior, 1 and 1/4 inches; transverse,
FIG.
Paranasal sinuses: (A) surface projection of the sinuses, (B) sagittal section
(semidiagrammatic), showing the 4 paranasal sinuses.
FIG.
Normal x-ray appearance of the paranasal sinuses in a lateral projection: (1)
frontal sinuses, (2) ethmoid cells, (3) sphenoid sinus, (4) maxillary sinuses,
(5) anterior clinoid processes of the sella turcica, (6) posterior clinoid
processes of the sella turcica, (7) sella turcica.
In front the
pyramid is bounded by the facial surface of the superior maxilla and behind by
the zygomatic surface of the same bone. This sinus lies lateral to the lower
half of the nasal cavity in front of the pterygopalatine and the infratemporal
fossae, below the orbit and above the molar teeth. The infra-orbital nerves and
vessels lie in the roof of the sinus, and their branches to the incisor, the
canine and the premolar teeth descend in the anterolateral wall. This nerve
produces infra-orbital facial pain when the maxillary sinus is diseased.
FIG.
X-ray projection for the upper half of the orbit, showing an effusion in the
right maxillary and the frontal sinuses. These should be compared with the
normal sinuses on the left side: (1) right frontal sinus, obliterated by
effusion; (2) left frontal sinus, normal appearance; (3) roof of the orbit; (4)
lesser wing of the sphenoid; (5) sphenoidal fissure; (6) greater wing of the
sphenoid; (7) right maxillary sinus, obliterated by effusion; (8) left
maxillary sinus, normal appearance; (9) zygoma.
The floor formed
by the alveolar margin is about 1/2 inch below the nose, and in it are
seen elevations produced by the roots of some of the upper teeth, the most
usual being the 1st and the 2nd molars. It is possible that all true maxillary
teeth (canine to the "wisdom") may be in relation to it. At times the
roots actually project into the sinus, but as a rule they produce a bulge into
the floor and are separated from the cavity by a thin layer of spongy bone.
This relationship between teeth and sinus explains the production of maxillary
disease by infected teeth and also the establishment of drainage for an empyema
of the sinus by removal of one of these teeth. The floor of the sinus is not
smooth, since it presents incomplete septa that form pockets in which inflammatory
products may stagnate. Such pockets may be inaccessible to treatment and must
be handled individually. The nerves and the vessels to the molar teeth descend
in the lower part of the posterior wall of the antrum. The sinus drains into
the infundibulum of the middle meatus of the nose by means of a maxillary
ostium; this opening varies from a tiny slit to a complete replacement of the
floor of the infundibulum. The maxillary sinus is more frequently the site of
disease than are any of the other accessory sinuses. Infection may take place
through the upper molar alveoli and by way of the nose. Tumors of the antrum
are not too uncommon; hence, knowledge of the surrounding anatomy is important.
A malignant tumor may grow rapidly and by pressure upward can encroach upon the
eyeball; growth downward may involve the palate and loosen the teeth; inward
extension would obstruct the nostril, and backward involvement would invade the
pharynx. Such growths should be treated by excision of the superior maxilla.
Surgery.
Acute nasal infections that are severe or have a tendency to persist may extend
to the maxillary sinus as well as to any of the other sinuses. Carious teeth
projecting into the sinus cavity may also be the cause of such infections, or
extension from adjacent sinuses (frontal, sphenoid and ethmoid) can be the
inciting agent. If pus is present in the maxillary sinus, it may be visible at
the middle meatus. Of all the nasal sinuses, the maxillary is the easiest to
irrigate. This can be done by one of four methods: by entering the natural
opening (ostium) or by perforating the nasoantral wall directly beneath the
inferior turbinate. Since the natural opening is placed at too high a level for
pus to escape, it may remain stagnant. Therefore, it becomes necessary to
explore or drain the antrum via another route. A needle is introduced through
the nostril and is passed outward and backward. It pierces the bone under cover
of the inferior turbinate (inferior nasal concha) and enters the sinus at a
much lower level than the natural orifice of the cavity. The sinus may also be
entered through the region of a tooth which is at fault after that tooth has
been extracted and a hole drilled upward through its socket and into the sinus.
This dental approach was used for many years in empyema of the antrum, but
unfortunately infections recurred from the mouth. This, plus insufficient
drainage, has resulted in its being discarded by some authorities. Another
approach to the maxillary sinus —by many believed to be the best—is that which
passes through the outer oral wall. The head is turned to the sound side, and
the lip is retracted upward and backward. An incision is made over the roots of
the teeth from the canine to the 2nd molar, and the periosteum is divided in
the same line and separated from the bone. The facial wall of the antrum is
opened by means of a small chisel, and the interior is curetted. Drainage into
the nares may be instituted by removing the anterior part of the inferior
turbinate.
FRONTAL
SINUSES The frontal sinuses, bilaterally placed cavities of variable extent
situated anteriorly between the two plates of the frontal bone, have been
considered as extensions of the anterior ethmoid cells. The anterior wall of
each sinus is responsible for the prominence of the forehead, which is situated
above the eyebrow. Although not present at birth and not usually recognizable
until the 7th year of life, this sinus may appear as early as the age of 2
years. It is separated from its fellow by a complete bony septum which is often
deviated to one side so that one sinus is larger. The septum thins as the
sinuses grow and at times may even disappear by absorption. This sinus is about
FIG.
Surgery of the maxillary sinus: (A) via the natural opening, (B) through the
naso-antral wall, (C) the outer oral wall approach, (D) dental approaches.
The maxillary
sinus thus becomes involved and produces its usual symptoms, which may divert
attention from the true source of the infection (frontal or anterior ethmoid
sinus disease). A fracture over the frontal sinus can be depressed without
injuring the cranial contents, but such fracture may be associated with
emphysema of the surrounding tissues due to communication with the nose.
Inflammation of the mucous lining of the frontal sinus may be secondary to an
infection in the nose; conversely, when pus forms within this sinus, it may
drain into the nasal fossa. If the communication with the nose is blocked
because of swelling of the lining membrane, it may give rise to serious
complications by destroying the internal table and infecting the cranial
contents; it may even perforate the wall of the orbit and produce serious eye
complications. An early diagnosis of the presence of pus in the frontal sinus
calls for opening into the sinus by trephining over the supra-orbital margin.
Extranasal
and Intranasal Approaches. Interference with the normal
ventilation or drainage of the frontal sinus is usually associated with marked
edema in the region of the middle meatus, and the middle turbinate becomes
tightly compressed against the lateral wall.
FIG.
Extranasal approach to a diseased frontal sinus.
A deviation
of the nasal septum also aggravates the condition, and if the inflammatory process
becomes purulent, empyema of the sinus results. When the frontal duct is open,
pus passing along the semilunar hiatus may involve the opening of the maxillary
sinus and produce a sinusitis here. Since the anterior ethmoidal cells open
with the frontal duct into the infundibulum of the semilunar hiatus, these
cells too may become involved in frontal sinus disease. Osteomyelitis or
abscess of the frontal bone may result and can terminate in meningitis. An intranasal
operation for sinus disease is utilized by some and is described under
surgery of the ethmoid cells.
The extranasal
or external approach is usually performed in the following way the eyebrow
is shaved, and an incision is made, beginning at the temporal end, extending to
the middle of the root of the nose and then curving downward to the base of the
nasal bone. The soft parts are freed from the bone, and then two incisions are
made in the periosteum. The first is placed just above and parallel with the
supra-orbital margin; the second passes over the frontal process of the
maxillary bone. These two incisions do not meet. The frontal sinus is opened,
thoroughly curetted, and its floor removed. The frontal process of the frontal
bone and as much of the lacrimal bone as is necessary are removed through the
second incision. This gives access to the ethmoid cells, and the ethmoid sinus
is curetted. The operation also permits access to the anterior wall of the
sphenoid sinus. Drainage is instituted by means of a tube that is placed in the
upper wound, carried under the bridge of the bone through the nose and out at
the nostril.
SPHENOID SINUS The sphenoid sinus, a large cavity
situated in the body of the sphenoid bone, is divided into right and left halves
by a complete bony septum usually bent to one side. Each half has been referred
to as a sphenoid sinus, and each has its own opening. The sinus may be limited
to the anterior part of the bone, but usually occupies the whole of its body,
extending into the wings of the sphenoid, the pterygoid process and even into
the basilar process of the occipital bone. Formation of the sinus begins in the
5th month of intrauterine life as a recess of the nasal cavity but
does not extend into the body of the sphenoid until the 7th year. Both sinuses
have important relationships above, below, in front and laterally. Above the
sphenoid sinus, the pituitary body and the optic nerve are found, the nerve at
times forming a ridge inside the sinus. This close relationship causes the
optic nerve to be involved in sphenoid sinusitis, giving rise to sudden loss of
vision (retrobulbar neuritis). The sinus is bounded below by the nose. In
front, the wall of the sinus separates it from the ethmoid air cells, and
laterally the cavernous sinuses containing the internal carotid artery and the
6th nerve are located. The abducens, the oculomotor and the trochlear nerves,
and the ophthalmic and the maxillary divisions of the trigeminal nerve may be
involved in disease of the sphenoid sinus, which is considered a "danger
spot" in the skull because of these important surrounding structures. Each
half of the sinus has an orifice of its own that opens into the highest meatus,
the spheno-ethmoid recess.
Surgery. The sphenoid
sinuses may be drained by an external route as described in operations
involving the frontal sinuses, or through a nasal route. In the nasal route the
posterior half of the middle turbinate is removed, and a small hook or curette
is introduced upon the anterior superior wall of the nasal cavity. The point of
this curette is carried downward and then turned forward and outward toward the
eye of the involved side. It is firmly pressed into the posterior ethmoid
labyrinth and then drawn forward and downward. The posterior wall of the
labyrinth is entirely broken down. The sphenoid sinus is located, entered,
and its anterior wall removed.
ETHMOID SINUSES (CELLS) There are from 8 to 10
very thin-walled intercommunicating cavities occupying the greater part of the
ethmoid labyrinth and known as the ethmoid sinuses. The boundaries of these
sinuses are completed by the frontal, the palatine, the sphenoid bones and the
superior maxilla. They have been divided arbitrarily into three sets: anterior, middle and posterior.
The anterior ethmoid sinuses open into the middle meatus on the floor of the
hiatus semilunaris; the middle ethmoid sinuses open into the middle meatus on
the surface of the bulla ethmoidalis; the posterior, into the superior meatus.
Above the ethmoid sinuses are the meninges and the frontal convolutions in the
anterior cranial fossa; in the front is the frontal sinus; behind is the
sphenoid; below, the nose; and laterally, the orbit. The ethmoid cells in each
labyrinth may vary from 4 large cells to 17 small ones, the average number being 9. These spaces are separated
from their surrounding structures by extremely thin plates of bone (lamina
papyracea); because of this, infection may spread to the surrounding parts
quite readily. This explains why ethmoiditis is the most common cause of
orbital cellulitis. The relations of the ethmoid air sinuses to the cranial
cavity are more extensive than those of the frontal and the sphenoid; hence,
meningitis, subdural abscess, cerebral abscess and sinus thrombosis may
complicate ethmoiditis. It should be recalled that the frontal sinus has been
considered as one of the anterior ethmoid cells.
Nasal Approach. Acute
inflammation of the ethmoid cells at times is associated with acute rhinitis
(common cold) and diseases of the frontal and the maxillary sinuses. The
diseased ethmoid sinus can be opened and drained externally by procedures that
have been described for frontal sinus drainage, but more frequently the nasal
route is used. A curette is introduced into the nasal cavity through the
vestibule and carried to the anterior attachment of the middle turbinate. This
is pressed firmly downward from the orbit and removes the anterior aspect of
the turbinate. The curette is carried through the turbinate, the hiatus
semilunaris removed, and entrance gained to the anterior.
FIG. Surgery
of the sphenoid and the ethmoid sinuses: (A) nasal approach to the ethmoid
sinuses (cells); (B) nasal approach to the sphenoid sinus.
Facial and Head Nerve
Blocks
Surgery
of the head is rarely performed with regional anesthesia alone, but facility
with blockade of the nerves of the head is useful in many diagnostic and
therapeutic pain procedures.
Sensory
fibers to the posterior scalp arise from the upper cervical roots and course
upward over the occiput as the greater and lesser occipital nerves. These
nerves can be blocked superficially on the posterior scalp or more centrally by
blockade of the deep cervical plexus. The anterior portion of the scalp and the
face are innervated by the branches of the trigeminal nerve. The three main
branches of this cranial nerve are the ophthalmic, maxillary, and mandibular.
These produce (respectively) the three main terminal sensory nerves of the
face: the supraorbital, the infraorbital, and the mental. These nerves can be
blocked at their superficial foramina or more centrally just beyond their
trifurcation and exit from the skull. The trigeminal nerve arises from the base
of the pons and sends its sensory fibers to the large gasserian (or semilunar)
ganglion on the superior margin of the petrous bone just above the foramen
ovale. Direct alcohol neurolysis of this ganglion for total trigeminal ablation
has been practiced in the past. The risks of intracranial spread of the
neurolytic solution are significant. Radiofrequency ablation by a neurosurgeon
using fluoroscopic guidance is more common today. The three branches of the
ganglion depart the skull through separate exits. The uppermost ophthalmic
nerve enters the orbit through the sphenoidal fissure. Its main branch, the
frontal nerve, bifurcates into the supraorbital and supratrochlear nerves. The
former exits the superior border of the orbit at the supraorbital notch, while
the latter departs the orbit more medially. The middle branch of the
trigeminal, the maxillary nerve, is also purely sensory, but it is somewhat
larger than the ophthalmic nerve. It exits the skull through the foramen
rotundum and crosses the sphenomaxillary fossa medial to the lateral pterygoid
plate to reenter the bone of the floor of the orbit in the infraorbital canal.
In the fossa, it gives off the sphenopalatine branches medially to the pharynx
and the orbital and posterior dental branches.
Occipital Nerve Block
The greater and lesser branches
of the occipital nerve emerge from under the muscles at the level of the nuchal ridge on the posterior scalp.
They can be easily blocked by a subcutaneous ridge of anesthetic solution.
The
anterior dental branches arise from the main trunk while in the canal. The
infraorbital nerve that finally emerges from the infraorbital foramen just
below the eye branches into the palpebral, nasal, and labial nerves. The
mandibular branch is the largest branch of the ganglion, and it exits the skull
through the foramen ovale. It lies just posterior to the lateral pterygoid
plate of the sphenoid bone. It contains the only motor fibers of the
trigeminal, the branches to the muscles of mastication. These nerves are
carried by an anterior branch that separates from the nerve just after its exit
from its cranial foramen. The posterior branch gives off an early
auriculotemporal nerve that provides sensory innervation to the auricular and
temporal regions of the lateral scalp. The main trunk continues as the inferior
alveolar nerve to the lower jaw. Its terminal branch is the mental nerve, which
exits the mental foramen to supply the lower lip and jaw. All three of the main
trunks lie deep and are well protected by the skull, the mandible, and the
zygomatic arch. The terminal branches are superficial, and their foramina are relatively
easily identified.
Trigeminal Nerve, Sagittal View
Each of the three main branches of the trigeminal
nerve exits the skull through its own foramen and provides sensory innervation
of the face and jaw.
Conveniently,
the three external foramina lie in the same sagittal plane.
Indications
Surgical indications for anesthesia of any of these pathways are rare.
Performance of cranial burr holes on the debilitated patient can be done with
occipital nerve blocks and field infiltration. Generally, anesthesia of the
branches of the trigeminal nerve is used only in attempts to diagnose and treat
pain complaints. Occasionally, a patient with tic douloureux involving a branch
of the trigeminal nerve will respond to block of the nerve with local
anesthetic or a neurolytic agent. Incapacitating pain of malignancy also can be
relieved by a neurolytic block, although the advent of radiation, chemother-
Terminal Branches of the Trigeminal Nerve
Each of the three terminal branches (the supraorbital,
infraorbital, and mental) exits its respective bony canal in the same sagittal
plane, approximately
apy,
and radiofrequency ablation techniques has made this requirement rare.
Occipital nerve block is occasionally useful in relieving some headaches, but
it is rarely an adequate long-term therapy.
Drugs. Any of the local
anesthetics in lower concentrations are appropriate for facial or head blocks.
Bupivacaine 0.25% is probably best for diagnostic blocks, since its longer
duration may help differentiate some physiologic pain complaints from those of
psychological origin and may help the patient who is considering a neurolytic
procedure. Alcohol is the preferred neurolytic agent for facial blocks, but
this therapy is usually reserved for patients who are not candidates for
radiofrequency ablation.
Occipital Nerve Block
The
greater and lesser occipital nerves emerge from under the muscles of the neck
on each side to become superficial at the level of the nuchal line, the
prominent ridge of bone extending from the mastoid to the external occipital
protuberance.
1. The
patient is asked to sit with the head flexed toward the chest.
2. The
external occipital protuberance is palpated, and an "X" is marked on
the involved side at this level just lateral to the insertion of the erector
muscles of the neck (usually
3. After
wiping the skin with an alcohol swab, a 23-gauge needle is inserted at the
"X" and is advanced gently until it contacts the bone. It is
withdrawn slightly, and a ridge of 3 cc of local anesthetic is injected under the
mark and on either side of it.
4. If
lesser occipital nerve block is also desired, the needle is then angled
anteriorly and laterally along the skull, and the subcutaneous injection is
extended from this area forward to the area of the mastoid process. A total of
5. Care
is taken not to advance the needle under the angle of the occiput toward the
foramen magnum.
6. If
anesthesia of the entire scalp is desired, the subcutaneous wheal is carried
around the entire circumference of the scalp, but it is angled so that it
crosses above the ear on each side and extends at this same level anteriorly.
Facial Anesthesia
The
three terminal sensory branches of the trigeminal nerve can be blocked at their
respective foramina. For all three blocks, the patient lies supine with the
head slightly elevated.
1. For
the supraorbital nerve, the supraorbital notch is palpated along the
superomedial rim of the orbit, usually
3.
The mental nerve canal of the mandible also lies
Maxillary Nerve Block
When
tic douloureux or neuralgia of the middle division (presenting as both facial
and upper dental pain) requires more proximal block, the maxillary nerve is
blocked in the sphenopalatine fossa.
1. The
patient lies supine with the head turned slightly away from the side to be
blocked.
2. The
zygomatic arch is identified and marked. The patient is then asked to open and
close the mouth slowly while an index finger explores the upper border of the
mandible. The mandibular notch will be felt moving up and down anterior to the
temporomandibular joint at the midpoint of the zygoma. An "X" is
marked over the notch at its deepest point.
3. After
aseptic preparation, a skin wheal is raised at the "X."
4. A
7.5-cm needle is introduced through the "X" and directed 45 degrees
cephalad and slightly anterior, aiming at the imagined position of the back of
the globe of the eye itself.
5. When
the pterygoid plate is contacted, the needle is withdrawn and redirected
slightly anteriorly. When the needle succeeds in passing anterior to the
pterygoid plate, the nerve lies about
6. If
paresthesias are not obtained, anesthesia can be achieved by injecting 5 cc
into the fossa
Lateral View of Major Branches of the Trigeminal
Nerve
The maxillary and mandibular branches emerge from the
skull medial to the lateral pterygoid plate, which serves as the landmark for
their identification. A needle introduced onto the plate can be advanced
anterior for the maxillary nerve and posterior for the mandibular nerve.
Mandibular Nerve Block
The
mandibular nerve also can be blocked for neuralgia, tic problems, or cancer
pain, but anesthesia here may induce some weakness of the muscles of
mastication.
1. The
position and superficial landmarks are the same as for the maxillary nerve
(steps 1 to 3).
2. A
5-cm needle is introduced through the skin wheal and directed medially and
slightly posteriorly. Less cephalad angulation is required. The needle will
usually be perpendicular to the skin in all planes.
Lateral pterygoid plate
Lateral Approach to the Maxillary Nerve
The needle is introduced through the skin just over
the notch of the mandible and is directed anterior and cephalad to identify the
pterygoid plate. As the needle is advanced anteriorly off the plate, the
maxillary nerve is encountered before it reenters the skull in the infraorbital
canal in the base of the orbit.
3. The
needle is advanced until bone is contacted. This will be the posterior border
of the lateral pterygoid plate. The needle is redirected posteriorly off the
plate and should contact the nerve 0.5 to
4. Paresthesias
of the jaw or teeth confirm identification of the nerve. If not obtained, they
may be sought by gently exploring cephalad and caudad. In the absence of
paresthesias,
Lateral Approach to the Mandibular Nerve
The needle is introduced the same as for maxillary
nerve block, but it is directed posteriorly. After contacting the pterygoid
plate, it is directed further posteriorly until it passes behind the plate,
where it should encounter the nerve.
5.
If alcohol is to be used, 1 cc will suffice, but paresthesias are essential.
Again, injection is painful, and the same precautions should be employed as
with the maxillary block.
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.