Infratemporal Fossa Approach Treatment & Management

Preoperative functional and neurological deficits have a significant impact on the postoperative recovery and functional rehabilitation of the patient. Preexistent lower cranial neuropathies (eg, CNs IX-XII) are common in patients with tumors that originate at or invade the parapharyngeal space, tumors that extend to the jugular foramen, or both. These patients present a wide spectrum of swallowing or speech problems including hypernasal or slurred speech, nasal regurgitation, dysphagia, aspiration, and dysphonia (CNs IX, X, XII).

Aspiration due to lower cranial neuropathies has life-threatening consequences. Findings on physical examination reflect the dysfunction of specific CNs and include decreased elevation of the ipsilateral palate (ie, deviation of the uvula to the non-affected side, CN IX and X), decreased mobility/strength of the tongue (ie, deviation to the involved side upon protrusion, CN XII), decreased supraglottic sensation, pooling of secretions in the hypopharynx, ipsilateral vocal cord paralysis (CN X), and atrophy and paralysis of the sternocleidomastoid and trapezius muscles (CN XI).

A tracheotomy (for tracheal toilette) and a gastrostomy tube (for nutrition, hydration, and administration of medications) are often necessary during the perioperative period. Alternatively, patients with a proximal vagal paralysis may benefit from a medialization laryngoplasty and an arytenoid adduction procedure. Laryngeal framework surgery may be performed concurrent with tumor removal or during the early postoperative period. Laryngeal framework surgery improves the glottic closure, thus decreasing aspiration risk and restoring an adequate cough. These improvements often obviate the need for a tracheostomy for the sole purpose of tracheopulmonary toilet.

Laryngeal framework surgery, however, does not improve the absence of afferent innervation. Thus, patients with lower cranial neuropathies remain at risk for aspiration and nutritional deficiencies. An experienced speech and language pathologist can assist with the monitoring of the patient, recommend modifications in diet, and provide intensive swallowing therapy.

Patients with severe deficits who do not respond to surgical, conservative, or combined means or those with severe cognitive problems still benefit from a tracheostomy to facilitate tracheal toilet and from a gastrostomy tube to facilitate postoperative feeding and decrease the risk of prandial aspiration.

Velopharyngeal insufficiency (VPI) may be corrected by a palatal lift prosthesis. Alternatively, a pharyngeal flap or a palatoplasty may be performed in those patients who do not tolerate the prosthesis.

Tumors in the ITF may cause eustachian tube dysfunction, which leads to conductive hearing loss, or such tumors may destroy the temporal bone or posterior cranial fossa, which leads to sensorineural hearing loss. Preexistent presbycusis also may compound the hearing loss. A myringotomy, amplification, or both will facilitate communication with the patient.

Trigeminal sensory dysfunction commonly is underdiagnosed. Preoperatively evaluate corneal sensation and eye protective mechanisms.

Patients with invasion of the facial nerve may have facial weakness or paralysis, facial spasms, and epiphora. A gold weight (implanted in the upper eyelid) or surgical tightening of the lower lid may be necessary to protect the cornea. Corneal anesthesia associated with lagophthalmos due to facial nerve palsy or other causes requires aggressive measures (eg, tarsorrhaphy) to prevent corneal injury.

Lateral deviation of the jaw upon opening may be due to paralysis or tumor invasion of the pterygoid muscles or problems of the temporomandibular joint (TMJ). Similarly, trismus may be due to mechanical effects of the bulk of the tumor, tethering of the muscles due to scarring, or tumor ankylosis of the TMJ, or pain. Severity and etiology of the trismus influences the perioperative management of the airway. Trismus due to pain resolves with the induction of general anesthesia. Conversely, if the extirpative surgery is expected to correct the trismus, a patient with mechanical trismus may require a nasotracheal intubation performed while awake, or, if trismus is expected to persist even after tumor removal, the patient may require a tracheostomy performed under local anesthesia.

Limitations of the extraocular movements may occur due to direct tumor invasion of the orbit, extraocular muscles, or both or due to invasion or compression of CNs III, IV, and VI. Thoroughly evaluate these nerves. The authors prefer a neuro-ophthalmological evaluation to elucidate these problems and to provide objective measures of the deficit. Similarly, patients with optic nerve problems or with tumor adjacent to the optic nerve, chiasm, or optic tract, are also referred for neuro-ophthalmological evaluation.

Anticipate the need for blood replacement. Preoperatively, type and cross the patient for 2-6 units of packed red blood cells (PRBCs) 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 or auto-transfusion device may be used during the resection of benign vascular tumors. Administer wide-spectrum perioperative antibiotic prophylaxis with good penetration of the blood-brain barrier before the surgery, and continue it for 48 hours postoperatively.

Somatosensory evoked potential (SSEP) monitoring of the median nerve is indicated whenever surgical manipulation of the ICA or the temporal lobe is anticipated. Lower CN monitoring is not routinely used, although it may be useful for the identification of nerves when the tumor is in close proximity to nerves. Facial nerve monitoring, however, is routinely used for transparotid or transtemporal approaches.

Several factors influence the choice of anesthetic agent and technique and, therefore, require thorough discussion with the anesthesiologist. These factors include (1) the extent of intracranial dissection, (2) the potential for brain or vascular injury, (3) systemic hemodynamics, (4) the need for monitoring of cortical and brainstem functions (eg, brainstem-evoked response, SSEP, EEG), and (5) the need for CN monitoring (ie, CNs VII, X-XII).

Secure the endotracheal tube with a circumdental or circummandibular wire ligature (eg, #26 stainless steel wire). Insert a lumbar spinal drain when intradural dissection is anticipated. Other measures to diminish the intracranial pressure, such as hyperventilation, osmotic diereses, or corticosteroids, are used as needed. Pass and secure a nasogastric tube and Foley catheter. Antiembolic sequential-compression stockings are recommended to prevent deep venous thromboses.

Position the head of the patient on a horseshoe-shaped head holder. Use "egg-crate" or gel padding to avoid ischemic ulcers of the scalp or back during a prolonged surgery. It is best to secure the head with a 3-pin head fixation system when a prolonged surgery or extensive intracranial neurovascular dissection is anticipated, or EMG monitoring is necessary (paralysis cannot be used). When proximal control of the ICA is required, or even possible, position the head in slight extension to facilitate access to the neck. Place tarsorrhaphy sutures for protection of the eyes. Shave the scalp, following the planned incision line (eg, bicoronal), and infiltrate the incision line with a solution of lidocaine and epinephrine (1:100,000-1:400,000).

For endoscopic approaches, position the head in a 3-pin fixation system and use a surgical navigation system. Decongest the nose using oxymetazoline 0.05%. Inject lidocaine and epinephrine solution as deemed necessary but observe maximum doses.

Preauricular (subtemporal) approach

Carry a hemicoronal or coronal incision through the subcutaneous tissue, galea, and pericranium as seen in the image below. Over the temporal area, the incision extends to the deep layer of the temporal fascia. On the affected side, extend the incision, following the preauricular crease down to the level of the tragus. Whenever possible, preserve the anterior branches of the superficial temporal artery to maximize the blood supply to the scalp flap. To provide proximal control of the ICA, extend the incision into the neck using a lazy-S pattern, or use a separate horizontal incision that follows a midneck crease. Elevate the scalp from the cranium following a subpericranial plane, and separate the attachments of the pericranium to the deep layer of the temporal fascia.

Superficial and deep layers of the deep temporal fascia attach to the lateral and medial surfaces of the zygomatic arch. To expose the zygoma, incise the superficial layer of the deep temporal fascia, following an imaginary line from the superior orbital rim to the zygomatic temporal root as seen in the image below. Elevate the superficial layer of the deep temporal fascia and periosteum with the scalp flap to protect the frontal branches of the facial nerve and to expose the orbitozygomatic complex. This exposure allows dissection of the periorbita from the lateral orbital walls (ie, from the trochlea to the inferior orbital fissure).

Using electrocautery, transect the remaining fascial attachments of the temporalis muscle to the medial aspect of the zygomatic arch and to the cranium, and elevate the muscle off the temporal fossa. If the temporalis muscle will be returned to its original position, screw a curved titanium plate at the temporal line, leaving some screw holes empty to facilitate suturing the fascia of the temporalis muscle to the plate. The image below depicts the exposed orbitozygomatic complex. The authors have obtained better results with this technique than that of leaving a fascial cuff or using drill holes through the bone to reattach the muscle.

Then, dissect the masseteric fascia from the masseter muscle and elevate the overlying parotid gland with a broad periosteal elevator. Although seldom necessary, the arc of rotation of the scalp flap may be increased by transecting the soft tissues anterior to the tympanic bone. Preserve a cuff of soft tissue around the main trunk of the facial nerve to prevent traction injury.

When necessary, the internal, common, and external carotid arteries, and the IJV, are exposed, dissected, and controlled using the cervical incision. Also, identify and preserve CNs X-XII. Perform orbitozygomatic osteotomies (1) posteriorly, at the zygomatic root; (2) superiorly, at the zygomaticofrontal suture; and (3) medially, at the zygomaticomaxillary buttress at the level of the zygomaticofacial nerve. An assistant protects the soft tissues of the orbit using a malleable or orbital retractor, while the surgeon places the tip of the reciprocating saw at the most lateral aspect of the inferior orbital fissure. Perform this osteotomy through the malar eminence, following a sagittal plane medial to the zygomaticofacial foramen.

Accidental entry into the maxillary sinus occasionally occurs. This entry is inconsequential unless the surgery involves an intradural dissection, which would open the possibility of a CSF leak, thus requiring closure of the antrostomy using fascia and/or pericranium free grafting. Hold free tissue grafts in place by compression against the opening. This compression is achieved by restoring and plating the orbitozygomatic bone graft to its original position.

The image below depicts possible orbitozygomatic osteotomies. All these osteotomies may be modified to account for tumor involvement of any portion of the orbitozygomatic complex. In cases requiring both intracranial and extracranial exposure, make the superior and lateral osteotomies through the superior and lateral orbital walls after completing the craniotomy. This way, the superior and lateral orbital walls can be preserved in the orbitozygomatic graft. Using both intracranial and extracranial exposures, make osteotomies through the superior and lateral orbital walls to remove the orbitozygomatic bone segment.

As previously described, the assistant protects and retracts the orbital soft tissues; another assistant protects and gently retracts the frontal lobe, while the surgeon completes the osteotomies. Keep the bone graft in saline solution until the tumor is removed. A mandibular coronoidectomy increases the arc of rotation of the temporalis muscle. Then, dissect the temporalis muscle inferiorly until the infratemporal crest is fully visible. A subperiosteal plane then is followed medially to dissect the soft tissues from the infratemporal cranium.

Dissection of the soft tissues from the infratemporal skull base is usually associated with troublesome bleeding arising from the pterygoid plexus. Control bleeding with bipolar cautery, cottonoids moistened in oxymetazoline 0.05%, Surgicel/Avitene packing, thrombin/gelatin paste or a combination thereof. Unipolar cautery stimulates V3, causing contraction of the mastication muscles and occasional cardiac arrhythmias. Removal of the skull base at the subtemporal area facilitates identification and dissection of neurovascular structures.

The lateral pterygoid plate is identified anteriorly. Anatomic relationships that are useful for the identification of infratemporal skull base structures include (in an anterior to posterior direction) (1) the posterior aspect of the lateral pterygoid plate, which is aligned with the foramen ovale, (2) the foramen spinosum, and (3) the spine of the sphenoid bone. These structures lie in a straight line of sight that is lateral to the canal of the ICA. Skull base relationships are depicted in the image below.

The pterygoid plates also provide a route of access to the inferolateral aspect of the sphenoid sinus, which may be entered between the second and third divisions of the trigeminal nerve. After these neurovascular structures are identified and preserved, extirpation of the tumor can proceed. This approach provides excellent access to the infratemporal skull base, orbital apex, and lateral maxilla. Tumors that do not involve the temporal bone or petrous portion of the ICA are adequately exposed with this approach. Dissection of the petrous ICA requires removal of the glenoid fossa as part of the orbitozygomatic bone graft.

Use a temporal craniotomy, as seen in the image below, for exposure of the superior aspect of the glenoid fossa.

Dissect the capsule of the TMJ free from the fossa, and displace it inferiorly. Then, using a reciprocating saw, make osteotomies that incorporate the lateral two thirds of the fossa. (Note that the ICA is located medial to the fossa.) The image below depicts the structures from posterior to anterior. This provides stability for the mandibular condyle following its reconstruction. However, the condyle is prone to anterior dislocation. Injury to the cochlea is possible if the osteotomies are made too far posteriorly. If additional exposure of the carotid canal and extratemporal ICA is necessary, the condylar neck fossa can be transected at the level of the sigmoid notch to remove the contents of the condylar fossa.

Additionally, to dissect the petrous segment of the ICA, transect the mandibular division of the trigeminal nerve at the foramen ovale. Once the ICA is mobilized from its horizontal canal, it can be transposed and/or retracted to facilitate the resection of tumor or to gain access to the petrous apex.

To address differing tumor extent and other clinical circumstances, a variety of modifications to this approach are possible. For example, tumors that invade the mandible require a partial mandibulectomy. In children, the distance from the body of the mandible to the infratemporal skull base is greatly foreshortened, and the access between the mastoid tip and angle of the mandible is wider than in adults. Thus, adequate exposure of the infratemporal skull base can often be achieved using a transcervical approach with superior transposition of the facial nerve. ^[11] A parotidectomy, as depicted in the image below, also may be performed to obtain negative margins or to enhance the exposure.

Following tumor removal, close any communication with the upper aerodigestive tract. A temporalis muscle flap may be used to obliterate the dead space and to protect the ICA. The temporalis muscle can be divided vertically, and the anterior half of the muscle may be transposed to obliterate the defect, while the posterior half of the muscle is transposed anteriorly to fill the temporal fossa defect. The orbital floor may be reconstructed with titanium mesh and then covered with a temporoparietal fascia flap or a temporalis muscle transposition flap. Similarly, defects of the lateral orbital wall can be reconstructed with titanium mesh. In selected patients, a pericranium or a scalp flap may be elevated to protect the infratemporal skull base. Extensive soft-tissue defects are best reconstructed with microvascular free tissue flaps. The bone grafts are then replaced and fixated in their original position using titanium alloy adaptation plates, wire, or braided nylon sutures.

Plating is preferred since it provides greater stability. If resection of the mandibular condyle is necessary to expose the petrous ICA, do not attempt reconstruction of the TMJ. Reconstruction of the TMJ after oncologic exenteration of the ITF does not significantly improve the postoperative function and may actually lead to scarring, ankylosis, and trismus. Repair periosteal and muscular attachments to the craniofacial skeleton to prevent retraction and/or sagging of the muscles and other soft tissues. Close the skin and mucosal incisions using a multilayered technique.

Postauricular (transtemporal) approach

Start a question mark or C-shaped incision in the temporal area, and extend it postauricularly into the mastoid region, curving down to follow a horizontal skin crease of the middle neck. If the middle ear is sacrificed as part of the approach or the tumor resection, and if the patient is at risk for a postoperative CSF leak, permanently close the external auditory canal (EAC) to prevent CSF otorrhea. Divide the EAC at the bony-cartilaginous junction, and close it using everting stitches. Reinforce this closure with a myoperiosteal U-shaped flap based on the posterior margin of the EAC. Alternatively, if the middle ear is spared, the canal may be preserved by placing the incisions in the conchal area.

The incision follows the margin of the conchal bowl and tragus, so that the scar is hidden. In the conchal area, incise the skin, cartilage, and perichondrium to communicate with the retroauricular plane of dissection. An incision inside the EAC is difficult to suture in a watertight fashion and tends to stenose. These incisions, placed laterally, facilitate the anastomosis of the EAC to the pinna at the end of the extirpative procedure. A Penrose drain can be inserted through the conchal defect in the skin and auricle flap to facilitate its retraction. Elevate the cervicofacial flap following a subplatysmal plane in the cervical area and a supra–superficial musculoaponeurotic system (supra-SMAS) plane over the parotid area. Elevation of the cervicofacial flap follows the deep layer of the deep temporal fascia over the cranium.

Identify the main trunk of the facial nerve, anterior to the EAC just distal to the stylomastoid foramen, as described for a parotidectomy. If circumferential mobilization of the main trunk is not necessary, preserve a cuff of soft tissue around the main trunk to minimize the possibility of a traction injury when the facial flap is retracted anteriorly. A "tail" (ie, superficial) parotidectomy enhances the access to the retromandibular area. A total parotidectomy is indicated when facing an epithelial malignancy of the parotid gland. Skeletonizing the main trunk of the facial nerve and its branches facilitates their retraction and, thus, the access to the ITF.

Resection of the main trunk of the facial nerve and its branches (ie, radical parotidectomy) is indicated when the nerve is invaded by the tumor. In these cases, direct attention to the cervical exposure to obtain proximal control of the common, internal, and external carotid arteries; the IJV; and CNs X-XII. Transect the sternocleidomastoid and digastric muscles from the mastoid bone. Transect the stylohyoid and stylopharyngeus muscles, and remove the styloid process. 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, thus providing a wider access to the ITF.

In patients who require a radical parotidectomy, a mastoidectomy provides the means to obtain proximal control of the neural margins and facilitates grafting of the nerve. Mastoidectomy also provides access to the jugular bulb and adjacent lower CNs. 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 ITF 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. 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.

Fisch approaches

Fisch described several lateral ITF approaches centered on the subtemporal exposure and rerouting of the facial nerve.

The Fisch A approach is indicated for lesions within the temporal bone, such as glomus tumors. This approach involves the exenteration of the middle ear, a subtotal petrosectomy, and a permanent anterior transposition of the facial nerve. The lower CNs, ICA, and IJV are controlled in the neck early during the procedure. The external ear canal is closed as a blind pouch.

The Fisch B and C approaches are designed to approach more anterior pathology involving the petrous apex and clivus. The critical maneuvers in the type B ITF approach are the reflection of the zygomatic arch and temporalis muscle inferiorly and removal of the bone of the skull base floor to provide access to the ITF. A critical step to this extradural exposure is the subtotal petrosectomy. This includes a canal-wall down mastoidectomy including complete skeletonization of the labyrinth, facial nerve, sigmoid sinus, middle and posterior fossa dura, and the jugular bulb, as well as exenteration of all hypotympanic air cells and skeletonization of the ICA.

The TMJ is disarticulated after incising the capsule and removing the articular disc. At this point, the bone of the glenoid fossa and the root of the zygoma are removed completely. Further skeletonizing of the carotid artery is possible along the lateral and anterior wall of the ICA. Complete exposure of the carotid artery permits its mobilization out of the carotid canal, providing free access to the petrous apex and clivus. The eustachian tube must be sutured closed to prevent ascending infection from the nasal cavity. Free abdominal fat fills the bone defect and a temporalis muscle flap then covers the fat and the skeletonized middle fossa dura and obliterates the condylar fossa. The orbitozygomatic graft is plated and the skin closed in a multilayered fashion.

The type C approach is an extension of the type B and is used for lesions of the anterior ITF, sella, and nasopharynx. The feature distinguishing the type C from the type B approach is resection of the pterygoid plates. This permits exposure of the lateral wall of the nasopharynx, eustachian tube orifice, posterior maxillary sinus, and posterior nasopharyngeal wall past the midline. Following completion of the type B approach, the lateral surface of the pterygoid process is identified and soft tissues are elevated.

In this fashion, the base of both medial and lateral plates of the pterygoid processes can be drilled away, exposing the lateral wall of the nasopharynx. The exposure permits full visualization of the peritubal area, which can be resected en bloc. Closure of the defect after type C ITF surgery is more difficult than in the type B approach. Although transposition of the entire temporalis muscle into the ITF is possible, free microvascular flaps are often necessary to provide adequate closure.

The type D approach is a preauricular ITF approach that uses orbitozygomatic osteotomies and resection of the floor of the middle fossa to expose the medial middle cranial fossa without a lateral temporal craniotomy. During the type D approach, the middle ear and eustachian tube are not obliterated, and conductive hearing is not sacrificed. In addition, the intratemporal facial nerve is not rerouted, and the petrous ICA is not fully exposed. Subtype D1 addresses tumors of the anterior ITF, while the subtype D2 is designed for lateral orbital wall lesions and high pterygopalatine fossa tumors. Although these preauricular approaches do not include a temporal craniotomy, the floor of the skull base can be drilled away to allow full access to the ITF.

Anterior transfacial approach (facial translocation)

Complete a Weber-Fergusson incision, and extend it down to the periosteum of the maxilla, nasal bones, and orbital rim. The traditional translocation approach, as seen in the image below, involves a horizontal incision over the superior edge of the zygomatic bone, extending into the lateral canthus, to meet the Weber-Fergusson incision.

Dissect the frontal branches of the facial nerve, use silicone tubing for entubulization, and transect. Reanastomose these nerve branches at the end of the case, using an entubulization technique. Subperiosteal dissection of the anterior maxilla exposes the infraorbital nerve, which is then transected and tagged. Next, an inferiorly based flap comprising the upper lip, cheek, lower eyelid, parotid gland, and the facial nerve is reflected inferiorly. Elevate the frontotemporal scalp flap in a subpericranial plane, and reflect it anteriorly to expose the supraorbital rims, as seen in the image below.

Preauricular approach with anterior exposure

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. The image below depicts osteotomies. Alternatively, the maxillary bone graft can be elevated as a vascularized graft attached to the cheek flap, as described by Catalano et al (1993). ^[12]

The temporalis and masseter muscles are dissected from the zygomatic bone with electrocautery. Osteotomies are completed as required for the removal of the maxilla, and the bone graft is removed. A temporal-subtemporal craniotomy is performed, and the temporalis muscle is reflected inferiorly. After completing these steps, the anterior, medial, and lateral boundaries of the ITF are well exposed. The pterygoid plates can be removed to provide further access to the medial ITF or nasopharynx. Their base can be removed to allow their resection en bloc with the maxilla.

A temporal-subtemporal craniotomy provides additional exposure superiorly and allows dissection of intracranial structures. Following 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. 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, which is tied to itself in the nasal cavity. The eye is closed with a temporary tarsorrhaphy for 10-14 days to prevent a lower eyelid ectropion.

Transorbital approach

A transorbital approach may be used to complement the exposures obtained with one of the previous approaches, thus enhancing the exposure of the orbital apex and cavernous sinus. ^[13] Reserve this approach for patients with benign tumors of the orbital apex and cavernous sinus who have lost vision because of tumor growth. A transorbital approach also may 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. 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. The advantages of this approach include improved cosmesis due to preservation of the globe, and excellent anterior and lateral exposure of the cavernous sinus and its associated structures.

Endoscopic transpterygoid approach

An endoscopic approach requires a wide corridor created with the removal of the middle turbinate ipsilateral to the lesion, a posterior septectomy, and bilateral wide sphenoidotomies. This allows a 2-surgeon, 4-hands technique, which involves the introduction of the scope, suction, and dissection instruments through both nares. Kasemsiri et al categorized the various endoscopic transpterygoid approaches and describe the steps necessary to create the appropriate surgical corridor.

The approach to the infratemporal fossa requires a medial maxillectomy with the option of removing the lateral wall of the inferior meatus and the pyriform aperture (endoscopic Denker). A posterior septectomy or a septotomy (located approximately 1.5 cm from the columella) allows for a contralateral transeptal approach. These two maneuvers assist in accessing the entire posterior maxillary sinus wall endoscopically. The sphenopalatine artery is ligated and cut and then the posterior and lateral maxillary sinus walls are removed. According to the needs for exposure, a sphenoidotomy may be extended toward the pterygoid recess of the sphenoid sinus, preserving the vidian artery and nerve, which will be inferior to the opening. A variable amount of the pterygoid plates are removed to access the infratemporal fossa.

If the tumor extends or originates at the nasopharynx or invades the pterygoid plates or eustachian tube, the latter 2 structures are removed below the level of the foramen rotundum (V2), but the vidian artery and nerve are usually sacrificed. The V2 can be transected and followed intracranially into the gasserian ganglion if it is involved by the tumor (perineural extension). A viable and preferable alternative is the use of a Hadad-Bassagaisteguy nasoseptal flap (the contralateral septal flap is harvested as the sphenopalatine artery is ligated on the ipsilateral side).

Endoscopic transoral approach

Chan et al described a novel transoral endoscopic approach to the infratemporal fossa and parapharyngeal space that uses the space between the mandibular ramus and maxillary tuberosity as the surgical corridor. They were able to explore the infratemporal fossa from the angle of the mandible to the greater sphenoid wing and resect pathology in four patients with only transient, minor complications. ^[14]

A cadaveric study by Patwa et al indicated that the critical structures of the infratemporal fossa can be adequately exposed through the far-medial transoral endoscopic assisted approach, with access to different areas of the fossa provided by two secondary surgical corridors, specifically, the superomedial and inferolateral triangles. ^[15]

Reconstructive considerations

Address functional and cosmetic deficits created by the tumor or the intervention in a single-stage surgery if safe for the patient. If temporary facial palsy is anticipated, corneal protection using lubricants, a temporary lateral tarsorrhaphy, or both are usually adequate. Grafting of the facial nerve, however, involves a longer recovery period. Thus, insertion of a gold weight implant into the upper eyelid is advisable. Static fascial slings or muscle transpositions are indicated when an immediate reconstruction of the facial nerve is not possible.

A temporalis muscle transposition flap suffices to separate the cranial cavity from the upper aerodigestive tract and to obliterate the dead space. Microvascular free flaps, such as the rectus abdominis flap (for soft tissue defects), latissimus dorsi flap (for myocutaneous or massive defects), or iliac composite flap (for defects requiring bone reconstruction), are indicated when the temporalis muscle or its blood supply will be sacrificed as part of the oncologic resection; when the patient requires a complex resection involving composite tissue flaps with skin, 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 (eg, microvascular surgeon) are informed accordingly.

When using an endonasal endoscopic approach, skull base defects that involve exposure of the ICA or a CSF fistula are repaired using collagen matrix (DuraGen) as an inlay graft, followed by the Hadad-Bassagaisteguy nasoseptal flap. This flap is based on the posterior nasal artery and can be designed to cover extensive defects of the skull base, including neurovascular structures. Its use needs to be anticipated and the flap harvested before the posterior septectomy because this destroys its blood supply. The flap is bolstered by expandable sponges, strip packing, or the balloon of a 12F Foley catheter. Alternatively, or if the HBF is not available, a temporoparietal fascia flap can be transposed into the defect via a transpterygoid tunnel.

Postoperatively, transfer the patient to a specialty unit for continuous cardiovascular and neurologic monitoring. Laboratory tests should rule out postoperative anemia and electrolyte imbalance. Screen patients who required multiple blood transfusions for transfusion-induced coagulation disorders. Provide mild narcotic analgesia; avoid sedation that could interfere with the neurologic evaluation.

If the ICA was dissected, ligated, or grafted, close monitoring of the patient's hemodynamic status and fluid balance is essential. Order a CT scan of the brain (without contrast) in the first or second postoperative day to screen for intracranial complications, such as cerebral contusion, edema or hemorrhage, fluid collections, or pneumocephalus. When grafting of the ICA is performed, obtain an angiogram in the early postoperative period to assess the patency of the graft and to detect pseudoaneurysm formation.

Keep the scalp and other wound drains to bulb suction until the drainage is less than 30 mL/day. Then, remove the drain and close the wound using an encircling stitch placed at the time of surgery. If the cranial cavity is entered, wall suction is contraindicated due to the risk of direct negative pressure on the CNS.

Follow-up is dictated by the nature of the tumor; the need for postoperative radiotherapy, chemotherapy, or both; and the adequacy of the resection. In general, examine high-grade malignancies every 6-8 weeks, low-grade malignancies every 2-3 months, and benign tumors every 6-12 months. Obtain an MRI three months after completion of all treatments, and repeat in 6-12 months.

Cranial neuropathies

Deficits of the trigeminal nerve are the most common morbidity of surgery of the ITF. The loss of corneal sensation, especially in someone with facial nerve dysfunction, greatly increases the risk of a corneal abrasion or exposure keratitis. Facial anesthesia may predispose the patient to self-inflicted injuries, including neurotrophic ulcers. The loss of motor function of the mandibular nerve causes asymmetry of jaw opening and decreased force of mastication on the operated side, which may be further impaired by the resection of the TMJ or mandibular ramus. Fisch reported recovery of fifth nerve function after iatrogenic transection in a significant proportion of his cases. ^[16]

Temporary or permanent facial nerve dysfunction is common after transposition for ITF dissection and tumor removal. The facial nerve can suffer an ischemic injury due to devascularization of its infratemporal segment or because of traction to the extratemporal segments. Expect a temporary paresis of the facial nerve with mobilization of the mastoid segment of the facial nerve. Frontal branches of the facial nerve are at risk of injury during elevation of the temporal scalp flap. Injury is usually the result of a dissection in a plane that is superficial to the superficial layer of the deep temporal fascia or the result of compression during retraction of the flap.

Trismus

Postoperative trismus is a common occurrence due to postoperative pain and to scarring of the pterygoid musculature and TMJ. Trismus improves dramatically if patients regularly perform stretching exercises for the jaw using devices such as the Therabite appliance. In severe cases, a dental appliance may be fabricated that gradually opens with a screw.

Infections

Infectious complications are rare. Predisposing factors include communication with the nasopharynx, seroma or hematoma, and CSF leaks. In general, obliterate the dead space to prevent fluid collection, which subsequently can be infected. Separate the cranial cavity from the sinonasal tract. The use of vascularized tissue flaps is preferred, especially when dissection of the ICA or resection of the dura mater has been performed.

Wound necrosis of the scalp flap

This situation is rare. Poorly designed incisions and prolonged use of hemostatic clamps may result in areas of ischemia, particularly around the auricle, that can make the tissue susceptible to secondary infection.

Neurovascular

Postoperative cerebral ischemia may result from surgical occlusion of the ICA, temporary vasospasm, and thromboembolic phenomenon. Surgical dissection of the ICA can injure the vessel walls, resulting in immediate or delayed rupture and hemorrhage. In the event that a repair of the ICA is not possible, permanently occlude it by ligation or by the placement of a detachable balloon or vascular coil. Perform the occlusion as distal as possible (near the origin of the ophthalmic artery). The potential for thrombus formation decreases with a short column of stagnant blood above the level of occlusion.

Cerebrospinal fluid leak

A watertight dural closure may be difficult to achieve around nerves and vessels. Most CSF leaks can be managed nonsurgically by placement of a pressure dressing and a spinal drain to diminish the CSF pressure. Surgical exploration and repair of the dural defect may be necessary if the CSF leak does not resolve within a week. CSF may also accumulate in the posterior nasal spine (PNS) during an endoscopic approach. Clear rhinorrhea develops when the patient starts to change positions in the early postoperative period.

The authors have encountered patients who develop profuse unilateral rhinorrhea in the postoperative period, which was misinterpreted as a CSF leak. These cases were all associated with surgical dissection of the petrous ICA and probably are due to loss of the sympathetic fibers that travel along the ICA en route to the nasal mucosa. This situation produces vasomotor rhinitis that may be treated with the use of anticholinergic nasal sprays or botulinum toxin injections. However, testing of the fluid for beta-2 transferrin is mandatory to rule out a CSF leak.

Prognosis is highly influenced by the completeness of the resection and the histologic diagnosis. The literature regarding the prognosis of patients with tumors of the ITF is sparse. In general, benign tumors arising or extending to the ITF, such as neurilemomas and juvenile angiofibromas, have an excellent prognosis. Their recurrence rate is 6-30%. Endoscopic approaches have yielded results that compare favorably with these numbers, but its use is reserved for highly selected cases.

Reports addressing the surgical treatment of malignant tumors often include a variety of histological diagnosis and a wide range of tumor extent and adjunctive treatments. Thus, it is difficult to ascertain the true oncologic success of an ITF surgery. Reports by Catalano, Cocke, and Terz and our experience with tumors of the paranasal sinuses that extend to the ITF suggest that an ITF approach allows the surgeon to provide a survival rate that is equivalent to that of tumors that do not extend into the ITF, 60-65%. ^{[4, 12, 17, 18]}

In a study by Prasad et al, use of a type A ITF approach achieved the gross-total removal of 166 out of 185 tympanojugular paragangliomas (89.7%), with recurrence developing in 4 cases (2.4%). ^[19]

Recently, endoscopic skull base approaches have been combined with a transoral robotic assisted approach for extensive skull base tumors. The surgical robot was used to dissect the infratemporal fossa, parapharyngeal space, and nasopharynx below the level of the eustachian tube (this area is very difficult if not impossible to access and safely dissect via a transnasal endoscopic approach). ^[20]

Furthermore, recent advances in imaging have allowed for virtual planning of surgical corridors to best access the skull base. These advances have the potential to improve surgery of the infratemporal fossa by expanding access, increasing dexterity via robotic surgical arms and improving preoperative planning. ^[21]