Surgical Approaches to the Infratemporal Fossa

Introduction

A variety of surgical approaches to the infratemporal fossa (ITF) have been developed to address pathologies in specific areas while attempting to preserve the function of key neurovascular structures. Indeed, intimate knowledge of the anatomy and a multidisciplinary evaluation are of foremost importance when considering a surgical approach to this complex area. The boundaries of the ITF are shown in Table 121.1 . Tumors may arise in the ITF or invade it by direct extension from surrounding structures, such as the parotid gland, the upper aerodigestive tract, the temporal bone, and the parapharyngeal space. A multidisciplinary approach, including review at a tumor conference, is important for proper evaluation and treatment, ensuring both effective treatment of disease and acceptable function and cosmesis.

TABLE 121.1

Boundaries of the Infratemporal Fossa

	Superior	Medial	Lateral	Anterior	Posterior
Bone	Temporal bone, greater wing of sphenoid	Lateral pterygoid plate, pterygopalatine fissure	Mandible, zygoma	—	Articular tubercle of the temporal bone, glenoid fossa, and condyle, styloid process
Muscle	—	Superior constrictor, pharyngobasilar fascia	Masseter, temporalis	Medial and lateral pterygoids, masseter	Prevertebral fascia
Foramina	Carotid canal, jugular foramen, foramen ovale, foramen spinosum, foramen lacerum	—	—	—	—
Nerves	Mandibular division of trigeminal nerve (V3), Pars nervosa of jugular foramen	—	—	—	CN IX, X, XI; sympathetic plexus
Arteries	Internal carotid artery	Internal maxillary artery	—	—	Internal carotid artery
Veins	Internal jugular vein	Pterygoid venous plexus	—	—	Internal jugular vein
Other	—	—	Parotid gland	—	—

Key Operative Learning Points

The surgeon must have detailed knowledge of key structures in the ITF.
There are a variety of approach options (open vs. endoscopic; preauricular vs. postauricular) to the ITF.
Tumor location within ITF, benign versus malignant pathology, and the potential risk to neurovascular structures should all guide multidisciplinary treatment planning, including the choice of surgical approach.

Preoperative Period

History

History of Present Illness

1.
Ask about any neurologic deficits, emphasizing dysfunction of any cranial nerves.
- a.
  Dysfunction of the trigeminal nerve is common for tumors in the ITF. This may present as localized numbness or dysesthesia in V1, V2, or V3 distribution and/or dysfunction of mastication, including malocclusion or deviation of the jaw due to mass effect or weakness/atrophy of the masticator muscle.
- b.
  Weakness of the face suggests tumor involvement either by compression or by direct invasion. However, it is important to counsel patients that intact preoperative function does not assure sparing of the nerve, and some approaches may lead to permanent weakness after manipulation or transposition of the nerve.
- c.
  Tumors approaching the jugular foramen may result in deficits of the lower cranial nerves (IX–XII), and tumors invading the temporal bone or posterior fossa may lead to sensorineural hearing loss and vestibular dysfunction.
- d.
  Patients with preoperative dysphagia and aspiration should be counseled that surgery may worsen these problems, and consideration may be given to placement of a feeding tube and/or tracheostomy.
- e.
  Conductive hearing loss due to unilateral Eustachian tube (ET) dysfunction with middle ear effusion may indicate compression of the ET by a tumor.
2.
Ophthalmologic history is important, including any visual loss or diplopia.

Past Medical History

1.
Any history of prior lesions, cancers, or other tumors in the head and neck or distant locations is important, particularly the details of management including head and neck surgery or radiation.
2.
The medical health and functional status of the patient are important, as surgery of the ITF may be a significant physiologic stress, depending on the pathology and reconstructive needs.
3.
If the patient smokes, counseling and cessation are important for both perioperative healing and long-term survival.

Physical Examination

1.
The infratemporal space is relatively inaccessible to direct visualization and palpation on physical examination. Subtle swelling of the temporal area above the zygomatic arch may be evident. It is essential to perform a thorough examination of the head and neck, with special attention to cranial nerve function, to assess both the tumor extent and the existing dysfunction.
2.
Evaluate for trismus, as this may provide information about possible spread into the pterygoid musculature or the temporomandibular joint (TMJ). Preoperative airway planning is essential as some patients with significant trismus may need fiberoptic intubation or even tracheostomy if a major resection and reconstruction are planned.
3.
Evaluate visual function and document visual acuity; evaluate hearing and document audiometric testing.
4.
If considering an endonasal endoscopic approach, perform nasal endoscopy to assess the anatomy and adequacy of the surgical corridor.

Imaging

1.
Because direct physical examination of the ITF is limited, radiographic imaging plays an essential role in precise tumor location and may suggest the type of pathology. Computed tomography (CT) and magnetic resonance imaging (MRI) are complementary, and often both are needed. The demonstration of bone involvement and widening of foramina is best seen on CT, while the evaluation of soft tissue planes and tumor extension along neural structures is best seen on MRI.
2.
It is critical to evaluate the functional status of the internal carotid artery (ICA) and its precise anatomic relationship to tumors of the ITF as these influence the selection of the approach. If there is any concern for ICA involvement following CT and MRI imaging, a magnetic resonance angiogram (MRA) or angiogram should be considered. If intraoperative manipulation of the ICA is likely, the team should consider preoperative evaluation of collateral cerebral blood flow with a balloon occlusion test. Consultation with a Neurovascular Surgeon may be warranted if intraoperative vascular bypass is a possibility.
3.
Evaluation of regional and distant metastatic disease is dictated by the histology and stage of the tumor.

Indications

1.
A wide variety of conditions can affect the ITF, including benign and malignant tumors, infections that arise from the dentition, paranasal sinuses and salivary glands (which may be fungal, bacterial, or polymicrobial), and other destructive or infiltrative pathologies (e.g., fibromatosis, soft-tissue radionecrosis). Not all lesions of the ITF require surgery, and the “radicality” of surgery will be different depending on the pathology at hand. Surgery for infectious problems of the ITF is reserved for those cases in which appropriate, culture-directed antimicrobials have not resolved the problem.
2.
Common neoplastic indications for ITF surgery include benign lesions, such as schwannomas, pleomorphic adenomas, vascular lesions (arteriovenous malformations, paragangliomas), and meningiomas (which may or may not have intracranial origin) and malignant tumors, such as rhabdomyosarcoma, malignant salivary tumors (from aerodigestive tract, parotid, or microscopic minor salivary rests), and extensions of mucosal cancers from the oral cavity, sinuses, or nasopharynx.
3.
Tissue biopsy with pathologic confirmation of the biologic behavior (benign vs. malignant) is necessary prior to any major extirpative surgery and may guide the degree to which aggressive measures (e.g., nerve sacrifice) are indicated. Open or transnasal endoscopic biopsy is often possible, but if the tumor is limited to a deep location, an image-guided fine-needle aspiration biopsy should be considered. Biopsies are usually not indicated for highly vascular lesions with characteristic imaging findings, such as glomus tumors. Open/invasive biopsy may be necessary to diagnose certain lesions, justified by noting that some pathologic processes (e.g., hematologic proliferative disorders, such as lymphoma, plasmacytoma, and metastasis from distant sites) will not benefit from surgical resection.
4.
If imaging reveals skull base or intracranial invasion, neurosurgical consultation is essential.
5.
When assessing the indications for tumor removal, also assess the medical fitness of the patient to have the surgery and the reconstructive needs and options.

Contraindications

1.
Medical comorbidities with a high risk for general anesthesia
2.
ICA involvement with failed balloon occlusion test
3.
Extensive invasion of brain parenchyma by a malignant lesion
4.
Lesions whose biologic behavior deems them not to be appropriate for surgical therapy (e.g., lymphoma, plasmacytoma)

Preoperative Preparation

1.
Depending on the approach, image-guided navigation based on high-resolution, thin-cut CT images and/or MRI may be used to assist with the confirmation of anatomic landmarks and tumor boundaries and may assist in planning the surgical trajectory.
2.
Blood products should be available, especially for highly vascular lesions, as the internal maxillary artery traverses the ITF, and the ICA is in close proximity. Preoperative embolization of the internal maxillary artery may be considered to minimize blood loss, although this may compromise reconstructive options.
3.
If a large defect is anticipated after extirpation, preoperative consultation with a microvascular reconstructive surgeon is essential. Additional testing (Allen’s test, vascular studies) may be necessary.
4.
A lumbar drain should be inserted if a significant intradural dissection with risk of cerebrospinal fluid (CSF) leak is anticipated.

Operative Period

Anesthesia

1.
General anesthesia is required. Preoperative evaluation of the airway is critically important to the safe induction of anesthesia. Depending on the patient, traditional induction and laryngeal exposure may be possible. In patients with trismus, preoperative aerodigestive abnormalities, or anticipated postoperative airway compromise, fiberoptic intubation or tracheostomy may be necessary.
2.
If neurophysiologic monitoring will be performed, it is important to communicate with the anesthesia team regarding the need for avoidance of paralytic agents.

Positioning

1.
The patient should be positioned supine. The head should be supported on an appropriate head holder or in Mayfield pins if intracranial neurovascular work is anticipated, depending on the needs of resection and the preference of the Otolaryngologist and Neurosurgeon.
2.
Access to the neck for vascular control is important if the ICA/internal jugular vein (IJV) are at risk.

Perioperative Antibiotic Prophylaxis

1.
Antibiotic prophylaxis should provide coverage against flora of the skin and upper aerodigestive tract. If intracranial surgery is anticipated, the use of an antibiotic with good penetration of the blood–brain barrier should be considered. Our patients without drug allergies receive intravenous cefazolin and metronidazole.

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