Lecture 2 .
Topographical Anatomy of the Lateral Facial Region of the Head.
Facial region of the Head
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 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 lip, 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.
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
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.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 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).
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.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.
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. 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.
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 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
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,
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. 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
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.
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
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-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 cc will usually suffice.
5. Care is takeot 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
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.
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, cc of solution may be injected
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.
