Diagnostic and Staging Work-up

Owing to the inaccessibility of the ITF to physical examination, radiographic imaging is a vital component of the evaluation. Computed tomography (CT) and magnetic resonance imaging (MRI) provide valuable information and are obtained using standard skull base protocols. CT is superior to MRI, showing the remodeling or erosion of neurovascular foramina or other bones of the skull base. MRI better delineates the soft tissue planes, the tumor–soft tissue interface, and the presence of tumor along neural and vascular structures (Fig. 54-1). CT and MRI are often complementary.

FIGURE 54-1 MRI shows soft tissue tumor involving infratemporal fossa. Even malignant tumors of infratemporal fossa may reach a large size before they are visible or palpable on physical examination. Patients with such tumors may present with facial numbness, pain, or difficulty with mastication.

Another crucial question is the relationship of the tumor to the ICA. Magnetic resonance angiography (MRA) and computerized tomography angiography (CTA) provide a noninvasive assessment of the vasculature of the ITF and brain. If preoperative embolization of the tumor is indicated (e.g., juvenile nasopharyngeal angiofibromas, paragangliomas), angiography is preferred over MRA. Angiography provides important information regarding the vascularity of the tumor, its relationship to the ICA, and the cerebral circulation and its collateral blood supply. Neither angiography nor MRA is adequate, however, to predict reliably the adequacy of the collateral intracranial circulation if sacrifice of the ICA is necessary.

If the risk for injury or sacrifice of the ICA is high, the collateral cerebral blood flow may be evaluated using angiography-balloon occlusion with xenon CT (ABOX-CT). A nondetachable balloon is inserted in the ICA via the femoral artery. The balloon is inflated for 15 minutes while the awake patient is monitored for any neurologic deficit. If the patient does not develop any deficit, the balloon is deflated, and the patient is transferred to a CT suite. A mixture of 32% xenon/68% oxygen is administered via facial mask for 4 minutes. CT shows the distribution of xenon, which reflects the blood flow within the cerebral tissue, providing a quantitative assessment of milliliters of blood flow per minute per 100 g of brain tissue. The process is repeated after reinflation of the arterial balloon. A computer calculates the differential of the xenon diffusion in the brain before and after the balloon inflation, identifying patients at risk for an ischemic stroke secondary to reduced blood flow after occlusion of the ipsilateral ICA (Table 54-1).⁹

TABLE 54-1 Xenon Computed Tomography

Despite a negative finding from ABOX-CT testing, patients can sustain ischemic brain injury because of the loss of collateral vessels that are not assessed by balloon occlusion testing (“watershed area”), or because of embolic phenomena. In addition, this test is performed under ideal and controlled circumstances, and does not account for the possibility of episodes of hypoxia, hypotension, or electrolyte and acid-base disturbances that may alter the brain’s hemodynamics. Every effort should be made to preserve or reconstruct the ICA and to diminish the possibility of embolus formation during the surgery. Other techniques that provide information regarding collateral cerebral blood flow include single photon emission CT (SPECT) with balloon occlusion and transcranial Doppler.

Histologic diagnosis should be obtained before the extirpative surgery whenever possible. Tumors amenable to a punch or open biopsy are approached in this manner. Tumors that are in deeper planes may be sampled by fine-needle aspiration biopsy. Rarely, a histologic diagnosis cannot be obtained before the approach because of the intrinsic limitations of fine-needle aspiration biopsy. Under these circumstances, a frozen section analysis, obtained via a skull base approach, may be sufficient to justify the resection of the tumor. Vital neurovascular structures, such as the ICA, the eye, and cranial nerves, should not be sacrificed, however, based on a frozen section analysis.

The extent of the evaluation to rule out regional or distant metastasis or to determine that the ITF tumor is a metastasis is dictated by the histologic type and stage of the tumor. CT scan of the neck is more sensitive than physical examination for the detection of regional lymphadenopathy. Patients presenting with tumors that metastasize hematogenously (sarcoma, melanoma) should undergo CT scan of the chest and abdomen and a bone scan. Cerebrospinal fluid (CSF) cytology is advised for patients with tumors that have invaded the dura. These patients are also at risk for “drop metastasis,” which should be ruled out by spinal MRI.

Rehabilitation Considerations

Functional or neurologic deficits that are identified preoperatively should be taken into consideration during the surgical planning and during postoperative care. These deficits often have a significant impact on the recovery and functional rehabilitation of the patient.

Dysfunction of the trigeminal nerve or the masticator muscles or both is commonly underdiagnosed. Cutaneous and corneal sensation should be assessed preoperatively. Corneal anesthesia associated with concomitant facial nerve palsy requires aggressive measures to prevent corneal injury.

Lateral deviation of the jaw on opening may reflect weakness or paralysis of the ipsilateral pterygoid muscles, invasion of the muscles, or dysfunction of the temporomandibular joint (TMJ). Likewise, trismus may be due to mechanical restriction caused by the bulk of the tumor, ankylosis of the TMJ, scarring, tumor tethering, or pain. The nature of the trismus is an important consideration in the perioperative management of the airway. Trismus secondary to pain resolves with the induction of general anesthesia, allowing safe oral endotracheal intubation. In patients with mechanical trismus, an awake nasotracheal intubation may be performed if it is anticipated that surgery would correct the trismus. Otherwise, a tracheostomy, performed under local anesthesia, is the safest perioperative airway.

Neoplastic invasion of the facial nerve may manifest with facial weakness or paralysis, facial spasms, epiphora, facial spasms, and dysgeusia. Significant destruction of the facial nerve by tumor may occur before the patient develops these clinical signs. A gold weight, implanted in the upper eyelid, or surgical tightening of the lower lid may be necessary to protect the cornea.

Hearing loss caused by a tumor of the ITF may be either conductive, resulting from eustachian tube dysfunction, or sensorineural, resulting from tumor involvement of the temporal bone or posterior cranial fossa. A myringotomy or amplification or both facilitate communication with the patient.

Deficits of the lower cranial nerves (CN IX, X, XI, and XII) are associated with tumors that originate in the parapharyngeal space or tumors that extend to the jugular foramen, or both. Patients with deficits of CN IX, X, and XII present with varying degrees of swallowing or speech problems, such as hypernasal or slurred speech, nasal regurgitation, dysphagia, aspiration, and dysphonia. Findings on physical examination reflect the involvement of specific cranial nerves, and include decreased elevation of the palate, decreased mobility and strength of the tongue with deviation to the involved side on protrusion, decreased supraglottic sensation, pooling of secretions in the hypopharynx, ipsilateral vocal cord paralysis, and decreased bulk and strength of the sternocleidomastoid and trapezius muscles. Patients with partial deficits of the lower cranial nerves (paresis) often experience a complete deficit (paralysis) after surgery, resulting in increased dysphagia and aspiration. Consequently, a tracheostomy for tracheal toilet and a gastrostomy tube for nutrition and hydration are often necessary during the perioperative period.

Laryngeal framework surgery (thyroplasty) performed during the extirpative surgery or the early postoperative period improves the glottic closure and decreases the risk for aspiration, often obviating the need for a tracheotomy for the sole purpose of tracheopulmonary toilet.^10–12 Laryngeal framework surgery allows the patient to compensate for the deficits using the remaining function (contralateral side) more effectively. Laryngeal framework surgery does not restore the motor or the sensory function. These patients remain at a higher risk for aspiration and nutritional deficiencies. Collaboration with an experienced speech-language pathologist, who can assist with the monitoring of the patient and the diet modifications and provide intensive swallowing therapy, is crucial to prevent the pulmonary and nutritional complications of aspiration. In patients with severe deficits or in patients with cognitive problems, strong consideration should also be given to placement of a gastrostomy tube to facilitate postoperative feeding and decrease the risk of prandial aspiration.

Velopharyngeal insufficiency may be ameliorated by a palatal lift prosthesis that pushes the soft palate against the posterior pharyngeal wall. Alternatively, a pharyngeal flap or a palatopexy may be performed in patients who do not tolerate the prosthesis.

Reconstructive Considerations

Most commonly, a temporalis muscle transposition flap is adequate to separate the cranial cavity from the upper aerodigestive tract and obliterate the dead space. Microvascular free flaps, such as rectus abdominis flap (for soft tissue defects), latissimus dorsi flap (for myocutaneous or massive defects), and iliac composite flap (for defects requiring bone reconstruction), are indicated when the temporalis muscle or its blood supply is sacrificed as part of the oncologic resection, when the patient requires a complex resection involving composite tissue flaps with skin or bone or both, or when the extirpative surgery leads to a massive soft tissue defect and dead space. These needs are usually anticipated during the surgical planning, and the patient and consultants (e.g., the microvascular surgeon) are informed accordingly.

Ideally, functional and cosmetic deficits created by the tumor or the surgery should be addressed in a single stage, concomitant with the oncologic resection. When a temporary facial palsy is anticipated, corneal protection using lubricants or a temporary lateral tarsorrhaphy or both is usually adequate. Grafting of the facial nerve involves a longer recovery period, however. Insertion of a gold weight implant into the upper eyelid is advisable. When an immediate reconstruction of the facial nerve is impossible, static fascial slings or muscle transpositions are indicated. Lower cranial nerve deficits may be ameliorated by laryngeal framework surgery, tracheotomy, or laryngotracheal separation, as previously discussed.

Other Perioperative Considerations

Preoperatively, the patient’s blood is typed and crossmatched for 2 to 6 U of packed red blood cells, according to the extent and nature of the tumor and surgery. Autologous blood banking is used when feasible, although it is frequently impractical. A Cell Saver autologous transfusion device may be used during the resection of benign vascular tumors.

Perioperative antibiotic prophylaxis with a wide spectrum against the flora of the skin and upper aerodigestive tract and that exhibits good penetration of the blood-brain barrier is administered before the surgery and is continued for 48 hours after the surgery. The use of a broad-spectrum cephalosporin with good CSF penetration (e.g., ceftriaxone) seems to be as effective as multiple antibiotic regimens.

Somatosensory evoked potential monitoring using the median nerve is indicated whenever surgical manipulation of the ICA is anticipated. Lower cranial nerve monitoring is not routinely employed. It may be useful for the identification and preservation of nerve function when the tumor is in close proximity to these nerves. Conversely, facial nerve monitoring is routinely used for transparotid or transtemporal approaches. Monitoring electrodes and lines for vascular access should be secured with sutures, staples, or adhesive dressings.

The choice of anesthetic agent is influenced by the extent of intracranial dissection, potential for brain injury, systemic hemodynamics, the need for monitoring of cortical and brainstem functions (e.g., brainstem-evoked response, somatosensory evoked potentials, electroencephalography), and the need for cranial nerve monitoring (CN VII, and X to XII). All these factors should be thoroughly discussed with the anesthesiologist.

When changes of head position during surgery are anticipated, the endotracheal tube should be secured with a circumdental or circum-mandibular wire ligature (No. 26 stainless steel wire). The operating table is positioned perpendicular to the anesthesia staff, and if intradural dissection is anticipated, a spinal drain is inserted and secured with sutures and adhesive dressing (e.g., Tegaderm, Op-Site). Other measures to diminish the intracranial pressure, such as hyperventilation, osmotic diuresis, and corticosteroids, are used as needed throughout the surgery.

A nasogastric tube and Foley catheter are passed and secured after adequate placement is corroborated. Antiembolic sequential compression stockings are recommended to prevent deep venous thrombosis.

Preauricular (Subtemporal) Approach

The preauricular approach is suited for tumors that originate in the ITF and intracranial tumors that originate at the anterior aspect of the temporal bone, or greater wing of the sphenoid bone, and that extend into the ITF.^5,13,14 It may also be combined with other approaches, such as a subfrontal approach to expose massive tumors that extend to the anterior and middle skull base. The preauricular approach does not provide an adequate exposure for the resection of tumors that invade the tympanic bone, however, and does not provide control of the intratemporal facial nerve or jugular bulb.

An incision, following a hemicoronal or bicoronal line, is carried through the subcutaneous tissue, galea, and pericranium (Fig. 54-2). Over the temporal area, the incision extends down to the deep layer of the temporal fascia. The anterior branches of the superficial temporal artery are preserved, ensuring adequate blood supply to the scalp flap. Ipsilateral to the tumor, the incision is extended following into the preauricular crease down to the level of the tragus. When proximal control of the ICA is warranted, the incision is extended into the neck using a lazy S pattern, or, alternatively, a separate cervical incision is performed. The scalp is dissected following a subpericranial plane, separating the attachments of the pericranium to the deep layer of the temporal fascia. The scalp flap is elevated from the deep temporal fascia using a broad periosteal elevator.

FIGURE 54-2 A, Bicoronal scalp incision is extended along preauricular skin crease. This incision may be continued into upper cervical region as a lazy S incision, or a separate cervical incision may be made for exposure of vessels and nerves. B, Scalp flap is elevated from underlying cranium, fascia, lateral orbital rim, zygomatic arch, and masseteric fascia. Plane of dissection is deep to superficial layer of deep temporal fascia (incised) and deep to parotid masseteric fascia.

Above the zygoma, the deep temporal fascia splits into superficial and deep layers, which attach to the lateral and medial surfaces of the zygomatic arch. To continue the surgical exposure, the superficial layer of the deep temporal fascia is incised following an imaginary line that joins the superior orbital rim to the zygomatic root. The dissection continues deep to this plane, elevating the superficial layer of the deep temporal fascia off the zygomatic arch (see Fig. 54-2). Fascia and periosteum are reflected anteriorly with the scalp flap. This maneuver protects the frontal branches of the facial nerve that are just lateral to the superficial layer of the deep temporal fascia. Elevation of the periosteum from the lateral surface of the zygomatic arch and malar eminence completes exposure of the orbitozygomatic complex. The periorbita is elevated from the lateral orbit using a Penfield No. 1 dissector, exposing the roof and lateral wall of the orbit down to the inferior orbital fissure.

The fascial attachments of the temporalis and masseter muscles to the zygomatic arch are transected using electrocautery. The attachments of the temporalis muscle to the cranium are transected with the electrocautery, and the muscle is elevated off the temporal fossa. If the temporalis muscle is to be returned to its original position at the completion of the surgery, a curved titanium plate (1.5 to 1.7 mm) is screwed at the temporal line, leaving some screw holes empty to facilitate suturing from the plate to the muscle (Fig. 54-3). Then the masseteric fascia is dissected from the masseter muscle, elevating the overlying parotid gland with a broad periosteal elevator (see Fig. 54-2). To increase the arc of rotation of the scalp flap, any soft tissue anterior to the tympanic bone can be transected from superior to inferior, down to the level of the facial nerve. The facial nerve is identified and preserved using a standard technique. It is helpful to preserve a cuff of soft tissue around the main trunk of the facial nerve to prevent a traction injury to the main trunk of the facial nerve.

FIGURE 54-3 Areas of bone removal are noted with dark stippling. Temporal craniotomy is performed in conjunction with orbitozygomatic osteotomy. Additional exposure of infratemporal skull base may be achieved by removal of subtemporal cranium (striped area) and resection of mandibular condyle (lightly stippled area).

Using the caudal limb of the incision, the sternocleidomastoid muscle is dissected laterally, and the carotid sheath is exposed. When necessary, the contents of the carotid sheath, including the ICA and common and external carotid arteries, and the internal jugular vein are exposed, dissected, and controlled. CN X to XII are also identified and preserved. Vessel loops are placed around these structures and secured with hemoclips rather than hemostats to avoid inadvertent traction.

Orbitozygomatic osteotomies are performed at the zygomatic root posteriorly, the zygomaticofrontal suture superiorly, and the zygomaticomaxillary buttress at the level of the zygomaticofacial nerve medially (see Fig. 54-3). Prior periorbital elevation off the lateral and inferior walls is necessary to identify the inferior orbital fissure and to complete the osteotomies of the orbitozygomatic complex. The tip of the reciprocating saw is placed in the most lateral aspect of the inferior orbital fissure; an osteotomy is performed through the malar eminence following a vertical imaginary line medial to the zygomaticofacial foramen. This osteotomy separates the zygoma from the maxilla. Accidental entry into the maxillary sinus may occur, requiring closure of the defect using fascia or pericranium free grafting or both. These free tissue grafts are held in place by compression against the opening when orbitozygomatic bone graft is replaced and plated at the completion of the surgery. All osteotomies are completed with a reciprocating saw transecting the bone in beveled or V-shaped manner in such a way that maximizes the exposure and facilitates replacement of the bone graft at the completion of the surgery. If tumor involvement of the orbit is present, the osteotomies are modified to secure a complete resection.

In cases requiring intracranial and extracranial exposure, the superior and lateral osteotomies are made through the superior and lateral orbital walls after the craniotomy is completed, and the brain is separated from the skull base. This way, the orbital walls can be incorporated in the orbitozygomatic graft. Using intracranial and extracranial exposures, osteotomies are made through the superior and lateral orbital walls to remove the orbitozygomatic bone segment. This approach provides excellent access to the infratemporal skull base, orbital apex, and lateral maxilla.

The temporalis muscle is reflected inferiorly until the infratemporal crest is fully visualized. A subperiosteal plane is followed to dissect the soft tissues from the infratemporal cranium. Bleeding from the underlying bone is controlled by the application of bone wax.

Fracturing or removal of the coronoid process increases the arc of rotation of the temporalis muscle. Care should be exercised when dissecting the medial aspect of the temporalis muscle, especially near its insertion (coronoid process) because the blood supply to the muscle (deep temporal artery from the internal maxillary artery) penetrates the muscle at this area. Likewise, the soft tissue at the sigmoid notch should be dissected carefully to prevent accidental injury to the internal maxillary artery that travels adjacent to the medial surface of the mandibular ramus.

Dissection of the soft tissues from the infratemporal skull base is usually associated with troublesome bleeding arising from the pterygoid plexus. Bleeding is controlled with the use of bipolar cautery or Cottonoids moistened in oxymetazoline 0.05%, or both. Unipolar cautery is seldom used because it stimulates V3, causing contraction of the mastication muscles and occasional cardiac arrhythmias.

A subtemporal craniectomy may aid in the identification of neurovascular structures piercing the infratemporal skull base and to augment the exposure. The lateralmost bone is removed using rongeurs. The origin of the lateral pterygoid plate at the skull base is identified anteriorly. Anatomic relationships that are useful for the identification of infratemporal skull base structures are shown in Figure 54-4, including the posterior curve of the attachment of the lateral pterygoid plate that is in alignment with the foramen ovale, foramen spinosum, and the spine of the sphenoid bone. These structures lie in a straight “line of sight” that is lateral to the canal of the ICA. The inferolateral aspect of the sphenoid sinus may be accessed by removing the bone (i.e., pterygoid plates) between the second and third divisions of the trigeminal nerve. The extirpation of the tumor can now proceed, including the involved soft tissue and bone. To continue the subtemporal exposure, the middle meningeal artery is clipped or cauterized using bipolar electrocautery and transected. Bleeding from the venous plexus that accompanies V3 through the foramen ovale may be controlled with absorbable knitted fabric (Surgicel) packing.

FIGURE 54-4 A, Base of skull showing anatomic relationships of carotid canal. Foramen ovale and foramen spinosum are in a direct line from lateral pterygoid plate to spine of sphenoid.

Lesions that do not involve the temporal bone or petrous portion of the ICA are adequately exposed with this stepwise approach. Dissection of the petrous ICA is necessary, however; the glenoid fossa is removed as part of the orbitozygomatic bone graft. It is first necessary to perform a temporal craniotomy for exposure of the superior aspect of the glenoid fossa (Fig. 54-5). The capsule of the TMJ is dissected free from the fossa and displaced inferiorly. If possible, the capsule and meniscus are preserved. With use of a reciprocating saw, osteotomies are made through the glenoid fossa, incorporating the lateral two thirds of the fossa (see Fig. 54-5). This maneuver avoids potential injury to the ICA that is located medial to the fossa. In addition, this modification provides stability for the mandibular condyle after reconstruction, although it can be prone to anterior dislocation. Injury to the cochlea is possible if the osteotomies are made too posteriorly. If additional exposure is necessary (i.e., carotid canal and extratemporal ICA), the condylar neck and contents of the condylar fossa can be transected at the level of the sigmoid notch and removed (Fig. 54-6).

FIGURE 54-5 Using intracranial and extracranial approaches, osteotomies of superior orbital roof, lateral orbital wall, and glenoid fossa are performed.

FIGURE 54-6 Tumor medial to mandibular division of trigeminal nerve and in close proximity to petrous portion of internal carotid artery. Additional exposure of internal carotid artery and removal of tumor often necessitate transection of mandibular division of trigeminal nerve.

To dissect the petrous segment of the ICA, it is necessary to transect the mandibular division of the trigeminal nerve at the foramen ovale (see Fig. 54-6). When the ICA is mobilized from its horizontal canal, it can be transposed or retracted to facilitate the resection of tumor, or to gain access to the petrous apex.

Approaches to the ITF are modified according to the extent of the tumor and other clinical circumstances. Tumors that invade the mandible mandate a partial mandibulectomy to obtain negative margins. In a pediatric patient, the distance from the body of the mandible to the infratemporal skull base is greatly foreshortened. Adequate exposure of the infratemporal skull base can often be achieved using a transcervical approach with superior transposition of the facial nerve.

After extirpation of the tumor, it is necessary to close any communication with the upper aerodigestive tract. If viable, a temporalis muscle flap is used to obliterate the dead space and protect the ICA (Fig. 54-7). Because of the branching pattern of the blood supply to the temporalis muscle, the muscle can be divided vertically, and the anterior half of the muscle may be transposed with an intact blood supply. The remaining posterior half of the muscle is transposed anteriorly to fill the temporal fossa defect.

FIGURE 54-7 Anterior portion of muscle may be transposed to fill infratemporal skull base defect, as illustrated with this temporalis muscle. Right temporalis muscle has been split vertically with preservation of its axial blood supply.

Defects of the orbital floor may be reconstructed with titanium mesh, which is then covered with a temporalis muscle transposition flap or temporoparietal fascia flap. Likewise, defects of the lateral orbital wall can be reconstructed with titanium mesh. In selected patients, anteriorly or posteriorly based pericranial scalp flaps may be elevated to provide protection of the infratemporal skull base. When the temporalis muscle is unavailable, massive soft tissue defects are best reconstructed with microvascular free tissue flaps.

The orbitozygomatic bone graft is replaced and fixated in its original position with titanium alloy adaptation plates, wire, or braided nylon sutures. Plating of the bone grafts is preferred because it provides greater stability. To avoid compression of reconstructive flaps, it is sometimes necessary to remove a portion of the zygomatic arch.

If resection of the mandibular condyle was necessary to expose the petrous ICA, reconstruction of the TMJ is not attempted. Reconstruction of the TMJ after oncologic exenteration of the ITF does not improve the postoperative function significantly, and may lead to scarring, ankylosis, and trismus.

Periosteal and muscular attachments to the craniofacial skeleton must be repaired to prevent retraction or sagging, or both, of the muscles and other soft tissues. The skin and mucosal incisions are closed using a multilayered technique

Postauricular (Transtemporal) Approach

The postauricular approach is designed to expose and resect lesions involving the temporal bone and extending into the ITF.^3,14 A question mark–shaped or C-shaped incision is started in the temporal area and extended, postauricularly, into the mastoid region, curving down to follow one of the midneck horizontal skin creases (Fig. 54-8).

FIGURE 54-8 A, Curvilinear incision is made from temporal area to mastoid bone and upper cervical region. Flap is elevated superficial to deep temporal fascia, deep to mastoid periosteum, and deep to platysma muscle. B, Conchal incision is preferable to incision of external auditory canal when permanent obliteration of the ear is not indicated.

If the middle ear is to be sacrificed as part of the approach or the tumor resection, and there is a risk of a postoperative CSF leak (intradural work), the external auditory canal (EAC) is closed permanently to prevent CSF otorrhea. The EAC is divided at the bony-cartilaginous junction and then closed using everting stitches. This closure is reinforced with a myoperiosteal U-shaped flap based on the posterior margin of the EAC. Alternatively, if the middle ear is to be spared, the canal may be preserved by placing the incisions in the conchal area (Fig. 54-8B). The incision follows the margin of the conchal bowl and tragus so that the scar would be hidden.

FIGURE 54-9 Fisch B approach. A, The external ear canal has been divided and sewn, the facial nerve is exposed, the internal carotid artery is exposed after a TMJ exenteration. B, V3 is exposed after a subtemporal craniotomy. Surgical exposure obtained after temporal craniotomy and reflection of temporalis muscle inferiorly. 1, temporal fat pad; 2, facial nerve.

In the conchal area, the skin, cartilage, and perichondrium are incised to communicate with the retroauricular plane of dissection. These incisions, placed laterally, facilitate the anastomosis of the EAC to the pinna at the end of the extirpative procedure. An incision inside the EAC is not recommended because it is difficult to suture in a watertight manner, and tends to stenose. A Penrose drain can be inserted through the conchal defect in the skin-auricle flap to facilitate its retraction. Elevation of the cervicofacial flap is carried in a subplatysmal plane in the cervical area, suprasuperficial musculoaponeurotic system plane over the parotid area, and following the deep layer of the deep temporal fascia over the cranium.

The main trunk of the facial nerve is identified anterior to the EAC just distal to the stylomastoid foramen, as is described for a parotidectomy. If circumferential mobilization of the main trunk is unnecessary, a cuff of soft tissue is preserved around its main trunk to minimize the possibility of a traction injury when the facial flap is retracted anteriorly. In selected cases, a “tail” parotidectomy may enhance the access to the retromandibular area. A total parotidectomy is indicated when facing an epithelial malignancy of the parotid gland. Skeletonization of the main trunk of the facial nerve and its branches facilitates their retraction and the access to the ITF. Resection of the main trunk of the facial nerve and its branches (radical parotidectomy) is indicated when the nerve is invaded by the tumor.

Attention is then directed to the cervical exposure to obtain proximal control of the common, internal, and external carotid arteries, and the internal jugular vein. CN X to XII are identified and preserved. The sternocleidomastoid and digastric muscles are transected at their insertion to the mastoid bone. The stylohyoid and stylopharyngeus muscles are transected, and the styloid process is removed. CN IX usually can be identified at this time, as it crosses lateral to the ICA.

A mastoidectomy and dissection of the vertical portion of the facial nerve allows the transposition of the facial nerve, providing a wider access to the infratemporal fossa (see Fig. 54-9). In patients who require a radical parotidectomy, a mastoidectomy provides the means to obtain proximal control of the neural margins and to graft the nerve. It also provides access to the jugular bulb and adjacent lower cranial nerves.

Orbitozygomatic osteotomies may be performed as previously described (preauricular approach). After the orbitozygomatic complex is removed, the anterior, superior, medial, and posterior boundaries of the infratemporal fossa are well exposed, and all major vessels are “controlled.” Completion of the infratemporal skull base approach, including a temporal craniotomy, is performed as described in the previous section. The extirpation of the tumor can now proceed, including the involved soft tissue and bone. Reconstruction of the defect follows the principles outlined in previous sections.

Lateral Fisch Infratemporal Fossa Approaches

Fisch has described an array of lateral infratemporal fossa approaches that are the prototypic otologic approaches to the ITF (Fig. 54-8,9,10)³. The hallmark of these approaches is temporal bone management emphasizing facial nerve rerouting and subtemporal dural exposure for wide access to the lateral skull base. Figure 54-10 illustrates the anatomic regions appropriate for the Fisch type A, B, and C approaches. The Fisch type A approach has been described in detail in Chapter 46 regarding its application in glomus jugulare surgery. The Fisch type B and C approaches are designed to approach more anterior pathology involving the petrous apex and clivus. The type C approach is an extension of the type B approach, and is used for lesions of the anterior ITF, sella, and nasopharynx. The Fisch type D is a preauricular ITF approach using an orbitozygotomy and resection of the floor of the middle fossa for medial dural exposure without a lateral temporal craniotomy.

FIGURE 54-10 Different exposures obtained with Fisch A, B, and C approaches to infratemporal fossa. EAC, external auditory canal; IAC, internal auditory canal; ICA, internal carotid artery.

Anterior Transfacial Approach (Facial Translocation)

The anterior transfacial technique is best used to approach sinonasal tumors invading the ITF, the masticator space, or the pterygomaxillary fossa, and for tumors of the nasopharynx extending into the ITF (Fig. 54-11).^7,13,14 A bicoronal incision with an ipsilateral preauricular extension is performed and extended through the subcutaneous tissue (see the section on preauricular approach). A Weber-Fergusson incision is completed and extended down to the periosteum of the maxilla, nasal bones, and orbital rim. During a “traditional” translocation approach, a horizontal incision is carried over the superior edge of the zygomatic bone, extending into the lateral canthus, to meet the Weber-Fergusson incision (see Fig. 54-11). The frontal branches of the facial nerve are identified and dissected as they cross over the zygomatic arch. They are then entubulated with silicone tubing and transected. These nerve branches are reanastomosed at the end of the case, using an entubulation technique.

FIGURE 54-11 Incisions and osteotomies for facial translocation approach as described by Janecka.^13,14

Subperiosteal dissection of the anterior maxilla exposes the infraorbital nerve, which is then transected and tagged to facilitate its identification and reanastomosis at the end of the case. Then, an inferiorly based flap including the upper third of the upper lip, entire cheek, lower eyelid, parotid gland, and facial nerve is reflected inferiorly. The frontotemporal scalp flap is elevated in a subpericranial plane. This flap is reflected anteriorly, exposing the superior orbital rims (see Fig. 54-11). Alternatively, the exposure can be achieved without the temporal incision by combining the preauricular approach with the anterior exposure provided by the Weber-Fergusson incision.

Orbitozygomatic osteotomies are performed and joined with the maxillary osteotomies to free the anterior face of the ipsilateral maxilla en bloc with the orbitozygomatic complex. Alternatively, the maxillary bone graft can be elevated as a vascularized graft attached to the cheek flap, as described by Catalano and Biller.⁸ The temporalis and masseter muscles are dissected from the zygomatic bone with electrocautery. Osteotomies are completed, and the bone graft is removed. The temporalis muscle is reflected inferiorly. Removal of the coronoid process increases the caudal arc of rotation of the temporalis muscle. After completion of these steps, the anterior, medial, and lateral boundaries of the ITF are well exposed.

In selected cases, the pterygoid plates can be excised to provide further access to the medial ITF or nasopharynx. A temporosubtemporal craniotomy provides additional exposure superiorly and allows dissection of intracranial structures (Fig. 54-12). After the tumor resection, the temporalis muscle may be used to obliterate the surgical defect and provide separation of the cranial cavity from the upper aerodigestive tract, as previously described.

FIGURE 54-12 Subtemporal craniectomy is performed to provide additional exposure and adequate resection margin of extracranial tumors. Maximal exposure of infratemporal and central skull base is achieved.

Periosteal and muscular attachments are repaired, and the incisions are closed using a multilayer technique. The conjunctiva is repaired with running 6-0 fast-absorbing suture. The lacrimal canaliculi are stented with Crawford silicone tubing that is tied to itself in the nasal cavity. The eye is closed with a temporary tarsorrhaphy for 10 to 14 days to prevent a lower lid ectropion.

Transorbital Approach

In selected cases, a transorbital approach may be used to complement the exposures obtained with one of the previous approaches enhancing the exposure of the orbital apex and cavernous sinus. This approach consists of transection of the orbital tissues posterior to the globe with preservation of the attachments of the orbital soft tissues, including the globe, to the scalp flap. The orbital apex is removed to provide direct anterior access to the cavernous sinus and cavernous ICA. This approach is reserved for patients with benign tumors of the orbita apex and cavernous sinus who have lost vision as a result of tumor growth. It may also be employed for low-grade malignant neoplasms with minimal involvement of the orbital soft apex or optic nerve to obtain complete tumor removal. Extensive involvement of the orbital soft tissues requires an orbital exenteration. The advantages of this approach include improved cosmesis, a result of the preservation of the globe, and excellent anterior and lateral exposure of the cavernous sinus and its associated structures.

A preauricular infratemporal skull base approach is performed, as previously described. The periorbita is elevated from the superior, lateral, and inferior walls of the orbit. The periorbita is then incised, and the orbital tissues are transected posterior to the globe using bipolar electrocautery and sharp dissection. A cuff of tissue remains at the orbital apex to provide an adequate tumor margin. The remaining periorbital attachments are elevated medially to allow complete displacement of the globe from the orbital cavity. Over the medial wall, the neurovascular bundles are clipped or cauterized and transected. The lacrimal duct is transected, and the sac is marsupialized. Using rongeurs, bone is removed from the lateral wall of the orbit to the superior orbital fissure. The contents of the superior orbital fissure and optic canal are transected to provide additional exposure of the orbital apex.

Because of the loss of orbital bone, enophthalmos results unless the orbital defect is reconstructed with bone grafts or titanium mesh. A temporalis transposition or free tissue transfer provides soft tissue augmentation and protection of the carotid artery.