Surgical Anatomy of Infratemporal Fossa

The Infratemporal Fossa (fossa infratemporalis; zygomatic fossa) – The infratemporal fossa is an irregularly shaped cavity, situated below and medial to the zygomatic arch. It is an anatomic space of great importance to neurological surgeons
specializing in skull base surgery. Multiple neural and vascular structures enter & exit the infratemporal fossa via foramina in the skull base^​1,2​.

The infratemporal fossa is the space located deep to the ramus of the mandible. The fossa is bounded anteriorly by the posterior surface of the maxilla and posteriorly by the styloid apparatus, carotid sheath and deep part of the parotid gland. Medially lies the lateral pterygoid plate and the superior constrictor muscle of the pharynx. Laterally lies the ramus of the mandible. The roof is formed by the infratemporal surface of the greater wing of the sphenoid. The infratemporal fossa has no anatomical floor, being continuous with tissue spaces in the neck.

Boundaries of Infratemporal Fossa

• Superior: base of skull, Inferior surface of greater wing of the sphenoid
• Inferior: Where the medial pterygoid muscle attaches to mandible near its angle.
• Anterior: Posterior aspect of the maxilla
• Posterior: Tympanic plate, mastoid & styloid processes of temporal bone.
• Medial: Lateral pterygoid plate
• Lateral: Ramus of the mandible
• Foramen ovale & spinosum open on its roof.
• Alveolar canals open on its anterior wall.

Contents of Infratemporal Fossa

Muscle:– 1) Inferior part of temporalis muscle. 2) Lateral & medial pterygoid muscles

Ligaments:– Sphenomandibular ligament

Vessels:- 1) Maxillary artery & branches, 2) Pterygoid venous plexus

Nerves:- 1) Mandibular Nerve & branches.
2) Chorda tympani branch of facial nerve
3) Inf. alveolar, lingual, buccal nerve.

The otic parasympathetic ganglion

Temporalis muscle

• Origin:-Temporal fossa & deep surface of temporal fascia.
• Insertion:-Medial surface, apex, ant. & post. border of coronoid process and ant. border of ramus of the mandible.
• Blood supply:-Deep temporal part of maxillary artery.
• Nerve supply:-Deep temporal branches of ant. mandibular nerve.
• Actions:- 1) Elevates & retracts mandible, 2) Side to side grinding movement.

Lateral Pterygiod Muscle

• ORIGIN: Upper head: Infratemporal surface of greater wing of sphenoid, Lower head: Lateral surface of lateral pterygoid plate
• INSERTION: Pterygoid fovea (in front of neck of mandible) and capsule & articular disc of TMJ.
• NERVE SUPPLY: Ant. division of mandibular nerve
• ACTION: 1) Side-to-side movement. 2) Pulls condylar process forward to depress .

Relations of Lateral Pterygiod Muscle

• Superficial: temporalis, masseter, ramus of mandible, maxillary artery, buccal nerve
• Deep: medial pterygoid, mandibular nerve, middle meningeal artery, otic ganglion
• Emerging through its upper border: deep temporal & masseteric nerves
• Emerging through its lower border: lingual & inferior alveolar nerves and maxillary artery
• Emerging between its 2 heads: buccal nerve, maxillary artery

Medial Pterygiod Muscle

• ORIGIN: Superficial head: Tuberosity of maxilla, Deep head: Medial surface of lateral pterygoid plate
• INSERTION: Medial surface of ramus & angle of mandible.
• NERVE SUPPLY: From trunk of mandibular nerve.
• ACTION: 1) Elevation of mandible, 2) Protrusion of mandible (when muscles on both sides act together), 3)Side-to-side movement (when muscles on both sides act alternatively)

Ligaments

Stylomandibular ligament:- Joins styloid process to angle of the mandible & is a thickened part of parotid sheath.
Sphenomandibular ligament:- Suspends mandible & descends from spine of sphenoid bone to lingula of mandible.
Pterygospinous ligament:- Join spine of sphenoid bone to post. border of lat. pterygoid plate.

Neurovasculature of Infratemporal fossa

The maxillary artery is bigger of 2 terminal branches of ECA.
Arises post. to neck of mandible & is divided into 3 parts based on its relation to lat. pterygoid muscle.
• 1st (Mandibular) part: Deep to condyle of mandible.
• 2nd (Pterygoid) part: Neighbourhood of lat. pterygoid muscle.
• 3rd (Pterygopalatine) part: Into pterygopalatine fossa

Venous Plexus

• Lies around & within lateral pterygoid muscle.
• Tributaries correspond to branches of maxillary artery.
• Plexus drained by maxillary vein which begins at post. end of plexus & unites with sup. temporal vein – Form retromandibular vein.
• Maxillary vein accompanies only 1st part of maxillary artery.
• It communicates with a) Inf. ophthalmic vein via inf. orbital fissure b) Cavernous sinus via emissary veins & c) Facial vein through deep facial vein.

Communications of Infratemporal Fossa

The infratemporal fossa communicates with
1) Temporal fossa Via space below zygomatic arch.
1) The orbit Via inferior orbital fissure.
2) The middle cranial fossa Via foramen spinosum, ovale, lacerum
3) The pterygopalatine fossa Via pterygomaxillary fissure

SURGICAL ANATOMY OF PTERYGOPALATINE FOSSA

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Apporaches for Infratemporal Fossa

These may be anterior, lateral or combinations.

Anterior

1. Transmandibular
2. Transfacial
3. Intraoral

Lateral

1. Transmandibular
2. Transzygomatic

Others

Fisch types A, B, C, and D, Facial translocation, Transcranial, Combined

Combinations^​1,2​

These approaches may be combined with a (fronto)temporal craniotomy as necessary. The ideal surgical approach to the infratemporal fossa should:

1. Provide increased and more direct exposure of the pathology and the adjacent neurovasculature with: a short straight line between the surgeon and the pathology, and a wide arc of exposure in three dimensions.
2. Be extensile, i.e. capable of being extended peroperatively.
3. Minimise brain retraction where exposure of the intracranial contents is required.
4. Have minimal morbidity functionally or cosmetically.
5. Result in minimal increase in overall operating time.
6. Avoid facial skin incisions.

TRANSORAL APPROACH

• Sup. gingivolabial sulcus posteriorly is close to tuberosity of the maxilla & provides access to lower part of the ITF.
• Does not provide enough exposure for removal of tumours,
• View obstructed by fatty tissue & there is no vascular control.
• Access for biopsy purposes if lesion low in ITF.
• Benign tumour may be removed via this.

TRANSANTRAL APPROACH

• Antral cavity entered via sublabial incision, from canine to 1st molar.
• Mucoperiosteal flap elevated till infraorbital foramen, To preserve infraorbital vessels.
• Window on anterolateral wall of antrum for exposure of complete posterior wall of maxillary sinus.
• Roots of canine & premolars are preserved.
• Antral mucosa of post. wall incised at its junction with medial, lateral & superior wall mucoperiosteal flap reflected down

TRANSPALATAL APPROACH

• Kornfehl et al. described transpharyngeal approach via palate.
• Nasopharynx reached via ‘S’-shaped incision vertically on soft palate & on to ant. pharyngeal arch towards side of lesion.
• Mucosa of lat. nasopharynx incised vertically, sup. constrictor muscle of pharynx split to enter medial part of ITF.

TRANSMAXILLARY APPROACH

• By Langenbeek in 1859, Osteoplastic technique for tumours of pterygopalatine fossa.
• An incision placed in buccal sulcus above attached gingivae between maxillary second premolars.
• Incision placed half cm. above apices of tooth to ensure viability of teeth.
• Mucoperiosteal flap raised. Nasal septum separated from anterior nasal spine & maxillary crest. Facial soft tissue retracted cranially.

. Osteotomy incision from one maxillary tuberosity to other.
• The incision passes just under zygomatic buttress & divides anterior nasal aperture.
• Medial maxilla wall osteotomy done via inf. meatus to palatine canal. At this stage the palate & inf. portion of maxilla remain attached by the pterygomaxillary suture, thin post. wall of maxillary sinus & bone forming canal of palatine vessels.
• Using a curved osteotome, maxilla separated & disimpacted downwards.
• The buttress of bone anterolaterally & at piriform nasal aperture are preserved so that they can be approximated at closure.

EXTENDED MAXILLECTOMY APPROACH

• Transantral approach with extended sublabial incision, from midline to maxillary tuberosity & carried down to periosteum.
• Post. wall of maxillary sinus widely excised for access to pterygomaxillary portion of the tumour.

The medial wall of the maxillary sinus and the nasopharynx is removed.
• Lateral extension of tumour exposed by removing the lateral wall of antrum.
• Combined with a transpalatal approach.
• Krause & Baker 1st used for surgical treatment of nasopharyngeal angiofibroma.

TRANSMANDIBULAR APPROACH

• 1st done by Conley & Barbosa. ITF communicates inferiorly with neck.
• If mandible is laterally retracted & medial pterygoid muscle is detached from its mandibular attachment, Then we can reach ITF.
• Good control of vessels & nerves & en bloc resection of nasopharynx, ITF , mandibular ramus & parotid gland.
• Modified by Attia et al, To obtain wide exposure without sacrifice of mandibular function & sensory supply of face & oral cavity.

Mandibular osteotomies To spare inf. alveolar nerve & vessels & positioned under intercondylar notch, above the opening of
mandibular canal & medial to mental foramen.
• Detachment of med. & lat. pterygoid muscles & sphenomandibular ligament allows mandibular segment to reflect sup.
• Provides direct access to ITF, Intermaxillary fixation performed.
• Preserves function, exposure is good & cosmetically acceptable.

MAXILLARY SWING

The maxillary swing approach is a varia-tion of the transmaxillary approach and provides wide access to the nasopharynx as well as to the pterygopalatine fossa and pterygomaxillary fissure; it also preserves soft palate function which is so vital for speaking and swallowing.
Indications for maxillary swing include:
• Surgical excision of residual or recur-rent nasopharyngeal malignancy, usual-ly carcinoma
• Resection of recurrent juvenile naso-pharyngeal angiofibroma
• Covering exposed internal carotid arte-ry following radionecrosis of the naso-pharynx after radiotherapy for naso- pharyngeal malignancy with pedicled or free flaps

Steps

• Incision – Weber Ferguson incision without gingivolabial component
• B/L tarsorraphy should be performed
• Inverted “U” shaped incision marked on hard palate
• After deepening facial incision, lacrimal sac skeletonized & sectioned at its lower end.
• Infra orbital nerve sectioned as it comes out of infraorbital foramen.
• Periosteum of inf. orbital wall elevated.

1. Osteotomy on frontal process of maxilla & maxillo zygomatic suture.
2. Maxillo-ethmoidal junction separated.
3. Hard palate mucoperiosteum elevated based on C/L greater palatine vessels & I/L greater palatine vessels cauterized & sectioned.
4. Straight osteotome placed bwt arms of v shaped notch on ant. nasal spine & hammered to separate maxilla down middle.
5. Whole maxilla with its attached cheek tissue swung like a door laterally exposing whole of nasopharynx.
6. Mass in nasopharynx can now be removed under direct vision.
7. Maxilla can be repositioned after surgery and secured in position by using miniplate & screws.

Transzygomatic approach

1) Preauricular incision & ant. displacement of the flap.
2) Section of the zygomatic arch.
3) Masseter & zygomatic arch displaced inferiorly.
4) Coronoid process sectioned, displaced upward with temporal muscle.

Fisch(1984) infratemporal fossa approach

1. Type A= Access to temporal bone right up to petrous apex, Glomus jugulare tumours
2. Type B= Cross petrous apex to basiocciput & clivus, Chordoma, petrous apex cholesteatoma.
3. Type C= Upto nasopharynx, parasellar , retromaxillary & paratubal regions.
4. Type D= Upto lat. orbital wall, infratemporal & PPF.

Le Fort I osteotomy approach

A) Proposed osteotomy site just above the level of nasal floor.
B&C) Incisions & bone cuts along anterolateral maxillary surface.
D) Separation of the nasal septum with an osteotome.
E) Separation of maxilla from the pterygoid plate with curved osteotome
F) Down-fracture of maxilla to allow access to maxillary sinuses, nasopharynx, and adjacent skull base.

COMBINATION OF APPROACHES

• Radical excision of tumours & relatively limited access obtained by any single approach have made combined
approaches necessary.
• It offers the patients the maximum benefit of the technical ‘know-how’ of the surgical team & the best opportunity for
surgical excision.

Combined infratemporal & PCF approach

• Subtemporal preauricular infratemporal fossa approach
• Mid facial degloving approach.
• In 1969, Terez et al -Craniofacial approach for tumors invading pterygoid fossa.
• In 1976, House & Hitselberger – Transcochlear approach for tumors medial to the IAC or from the clivus.

SURGICAL ANATOMY OF PTERYGOPALATINE FOSSA

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References –

Pics – https://www.bartleby.com/107/pages/page184.html

http://www.ent.cuhk.edu.hk/images/publication/head-and-neck-dissection-and-reconstruction-manual/10_MAXILLARY-SWING-APPROACH-TO-THE-NASOPHARYNX.pdf

http://www.entdev.uct.ac.za/guides/open-access-atlas-of-otolaryngology-head-neck-operative-surgery

https://books-library.online/files/download-pdf-ebooks.org-1519303073Em1A7.pdf

https://www.slideshare.net/adityatiwari9235/

1. 1.

   Watkinson JC, Clarke RW. Scott-Brown’s Otorhinolaryngology and Head and Neck Surgery: Volume 1: Basic Sciences, Endocrine Surgery, Rhinology. CRC Press; 2018. https://books.google.co.in/books?id=3NFfDwAAQBAJ.
2. 2.

   Kalra G, Midya M, Bedi M. Access to the Skull Base – Maxillary Swing Procedure – Long Term Analysis. Ann Maxillofac Surg. 2018;8(1):86-90. doi:10.4103/ams.ams_5_18