Infratemporal Fossa - Complete ENT Reference

1. Overview

2. Boundaries

3. Communications

4. Contents

A. Muscles

Lateral Pterygoid Muscle

• Two heads:
  • Superior head: arises from the roof of the ITF - inferior surface of the greater wing of sphenoid and infratemporal crest, lateral to foramen ovale and spinosum
  • Inferior head (larger): arises from the lateral surface of the lateral plate of the pterygoid process
• Insertion: Pterygoid fovea of neck of mandible + capsule/articular disc of TMJ
• Action: Fibers oriented almost horizontally - major protruder of the jaw; pulls articular disc and condyle forward onto articular tubercle; bilateral action = protrusion; unilateral = side-to-side grinding
• Nerve supply: Nerve to lateral pterygoid from V3

Medial Pterygoid Muscle

• Two heads:
  • Deep head: medial surface of lateral pterygoid plate + pyramidal process of palatine bone
  • Superficial head: tuberosity of maxilla + pyramidal process of palatine bone
• Insertion: Roughened medial surface of ramus + angle of mandible
• Action: Primarily elevates mandible; assists in protrusion and grinding (passes obliquely)
• Nerve supply: Nerve to medial pterygoid from V3

Other muscles present:

• Temporalis (insertion on coronoid process within ITF)

B. The Sphenomandibular Ligament

5. Vascular Contents

The Maxillary Artery

Three Parts of the Maxillary Artery

• Deep auricular artery - supplies EAC and outer surface of tympanic membrane
• Anterior tympanic artery - supplies inner surface of tympanic membrane
• Middle meningeal artery - ascends between sphenomandibular ligament and lateral pterygoid, passes between two roots of auriculotemporal nerve, enters cranial cavity through foramen spinosum; largest meningeal vessel, supplies dura, bone, and bone marrow of cranial cavity walls (injury = extradural hematoma)
• Inferior alveolar artery - descends to enter mandibular canal with inferior alveolar nerve; supplies all lower teeth, buccal gingivae, chin, lower lip; gives mental artery
• Accessory meningeal artery

• Deep temporal arteries (anterior + posterior) - supply temporalis muscle, travel with deep temporal nerves around the infratemporal crest
• Masseteric artery - to masseter
• Buccal artery - to buccinator
• Pterygoid branches - to pterygoid muscles

Pterygoid Venous Plexus

• Lies around the pterygoid muscles within the ITF
• Drains posteriorly into the maxillary vein
• Drains anteriorly into the facial vein
• Anastomoses with: cavernous sinus (via emissary veins through foramen ovale), ophthalmic veins, and pharyngeal venous plexus
• Clinical significance: Infection in the ITF can spread hematogenously to the cavernous sinus and orbit through these anastomoses

6. Neural Contents

A. Mandibular Nerve (CN V3)

Trunks and Branches:

1. Meningeal branch (nervus spinosus) - re-enters cranial cavity through foramen spinosum with middle meningeal artery; sensory to dura of middle cranial fossa and mastoid cells
2. Nerve to medial pterygoid - motor; also sends branches to tensor tympani and tensor veli palatini

B. Chorda Tympani Nerve

• Originates from the mastoid segment of the facial nerve (CN VII) midway in the descending portion
• Travels through the tympanic cavity (anterior superior quadrant of the mesotympanum)
• Exits via chorda tympani canaliculus in the petrotympanic fissure
• Descends vertically and medially to the lateral pterygoid muscle
• Joins the lingual nerve within the ITF
• Carries: taste from anterior 2/3 of tongue + preganglionic parasympathetic fibers to submandibular ganglion (for submandibular and sublingual salivary glands)

C. Otic Ganglion

• Located just below foramen ovale, medial to V3
• Parasympathetic relay ganglion: receives preganglionic fibers from lesser petrosal nerve (derived from CN IX, via tympanic plexus)
• Postganglionic fibers hitch a ride on auriculotemporal nerve to parotid gland
• Also receives sympathetic fibers from plexus on middle meningeal artery

D. Lesser Petrosal Nerve

• Exits middle cranial fossa through foramen ovale (or a small canal near it) to reach otic ganglion
• Carries preganglionic parasympathetics from glossopharyngeal nerve (CN IX)

7. Ligaments and Other Structures

• Sphenomandibular ligament: spine of sphenoid to lingula of mandible; contains the inferior alveolar nerve, artery, and vein as they pass through the mandibular foramen
• Temporomandibular joint: TMJ disc and capsule within the ITF laterally

8. Clinical Importance of the ITF

1. Tumor pathway: The ITF is a common route of spread for nasopharyngeal carcinoma, parotid malignancies, juvenile nasopharyngeal angiofibromas, trigeminal nerve tumors, and skull base tumors
2. Infection spread: Odontogenic infections, parapharyngeal abscess, and mastoid infections can enter and spread via the ITF; the pterygoid plexus allows hematogenous spread to cavernous sinus
3. Trismus: Pterygoid muscle spasm/fibrosis from infection, tumor, or post-irradiation leads to restricted jaw opening (trismus) - a hallmark sign of ITF involvement
4. Nerve entrapment: Tumors can compress V3 causing jaw pain, numbness, and jaw deviation on opening (motor root involvement)
5. Bleeding: The pterygoid venous plexus is notoriously difficult to control surgically; maxillary artery branches can cause significant hemorrhage
6. Surgical landmark: The ITF is the gateway to the lateral skull base; the Fisch approach uses it as the operative corridor

9. Fisch Infratemporal Fossa Approach

FISCH TYPE A APPROACH

• Glomus jugulare/tympanicum tumors (most common indication)
• Salivary gland cancers of temporal bone
• Squamous cell carcinoma of EAC
• Cholesteatoma of temporal bone
• Neurinoma, meningioma
• Rhabdomyosarcoma, teratoma, myxoma

Step-by-Step Surgical Technique:

• Cartilaginous EAC is transected
• Lateral canal skin released circumferentially from EAC soft tissue, tragal and conchal cartilage, then everted through the meatus and closed primarily
• A periosteal flap (anteriorly pedicled, from the mastoid) reinforces the closure medially - sewn to its undersurface

• Skin of osseous EAC elevated to the tympanic annulus
• Middle ear entered; incudostapedial joint separated; incus removed
• Tensor tympani tendon released; EAC skin and TM removed with attached malleus

• Bleeding controlled with packing (particularly from inferior petrosal sinus entering jugular bulb medially)
• Glomus tumors: dissect visible tumor, polish involved bone with diamond burr
• If intracranial extension < 2 cm: posterior fossa dura opened, tumor excised at same sitting; > 2 cm may require staged removal

• Dural reconstruction with fascia/lyophilized substitute/fat
• Abdominal fat obliterates temporal bone dead space
• Temporalis muscle rotated inferiorly to reinforce EAC closure

FISCH TYPE B APPROACH

• Chordoma, chondroma, chondrosarcoma
• Squamous cell carcinoma of petrous apex
• Dermoid/epidermoid cysts of petrous apex
• Meningioma, craniopharyngioma
• Plasmacytoma, arachnoid cyst

Additional Steps Beyond Type A Base:

1. Steps of Type A approach performed up to facial nerve stage (nerve NOT transposed)
2. Zygomatic osteotomy: Zygoma transected, temporalis muscle reflected (still attached to coronoid process and zygoma) - allows retractor to expose superior ITF
3. Mandibular dislocation: Self-retaining retractor dislocates mandibular condyle inferiorly, providing wide exposure
4. Middle meningeal artery transected - limits of operative exposure defined by middle cranial fossa floor, mandibular condyle, and reflected temporalis
5. CN V3 (mandibular nerve) transected - exposes superior 4 cm of ITF
6. Eustachian tube separation: Carotid artery uncovered from vertical segment to anterior limit at foramen lacerum after separation from eustachian tube soft tissues
7. ICA elevation: Artery can be elevated from foramen lacerum to canalis caroticus to permit temporary transposition; permits access to petrous apex and clivus
8. For extensive petrous apex lesions (especially with nonserviceable hearing): may add transotic or transcochlear approach

FISCH TYPE C APPROACH

• Salvage surgery for nasopharyngeal squamous cell carcinoma
• Adenoid cystic carcinoma around eustachian tube
• Advanced juvenile nasopharyngeal angiofibroma (JNA)
• Extensive clival and parasellar tumors

1. All type B steps performed
2. Greater superficial petrosal nerve (GSPN) may be cut
3. Facial nerve may require posterior transposition (cutting GSPN + mobilizing from porus acusticus to stylomastoid foramen) - significant permanent facial weakness risk
4. Additional middle fossa and clival exposure via combined temporal craniotomy
5. Anterior access to: sphenoid sinus, nasopharynx, pterygopalatine fossa, cavernous sinus

Summary: Fisch Approach Comparison

10. Reconstruction After ITF Surgery

• Dead space obliterated with abdominal fat graft (primary method)
• Temporalis muscle flap rotated inferiorly/posteriorly
• Microvascular free flap (for extensive defects)
• Allogenic tissue matrix recontouring
• Dural repair: autogenous fascia, lyophilized dural substitute, fat strips
• External auditory meatus is sewn shut (a permanent result of Type A)
• Layered wound closure + pressure dressing for 24 hours

11. Complications of ITF Approaches

• Facial nerve palsy (most significant morbidity; permanent in transposition approaches)
• Conductive hearing loss (EAC closed, ossicles removed)
• Sensorineural hearing loss (if otic capsule violated)
• Lower cranial nerve deficits (IX, X, XI, XII) - dysphagia, hoarseness, aspiration
• Numbness of face and jaw (V3 division sacrifice)

• ICA injury - catastrophic; requires preoperative balloon occlusion test
• Sigmoid sinus/jugular bulb bleeding
• Pterygoid venous plexus hemorrhage

• CSF leak
• Meningitis
• Wound infection
• TMJ dysfunction
• Trismus (late)

12. Preoperative Considerations for ITF Surgery

1. CT and MRI of temporal bone and skull base - define extent of disease
2. Angiography + balloon occlusion test - mandatory when ICA is at risk; assess cerebral collateral flow
3. Audiometry - baseline hearing and vestibular function
4. Lower cranial nerve assessment - preoperative function status
5. MRI brain - detect intracranial extension

Sources

• Cummings Otolaryngology Head and Neck Surgery, 7th ed., Chapter 175 (Anatomy of ITF) and Chapter 178 (ITF Approaches)
• KJ Lee's Essential Otolaryngology, 11th ed., Chapter 37 (Head and Neck Spaces) and Chapter on Surgery of the ITF
• Gray's Anatomy for Students, 4th ed., Chapter 8 (Head and Neck)