Infratemporal Fossa
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Direct answer
Below the temporal fossa and medial to the ramus of the mandible lies the infratemporal fossa, the deep workspace of the head containing the two pterygoid muscles, the maxillary artery's first and second parts, the mandibular nerve with its otic ganglion, and the chorda tympani joining the lingual nerve. Its roof is the infratemporal surface of the greater wing of the sphenoid, pierced by the foramina ovale and spinosum, which is why the mandibular nerve and middle meningeal artery drop straight into the fossa. Its venous plexus around the pterygoid muscles communicates with the cavernous sinus through emissary veins — the anatomical route by which dental and facial infection reaches the cavernous sinus.
What you must remember
- Boundaries: anteriorly the posterior surface of the maxilla; medially the lateral pterygoid plate of the sphenoid; laterally the ramus and coronoid process of the mandible; roof the infratemporal surface of the greater wing of sphenoid; posteriorly the styloid apparatus; it opens freely downwards into the neck.
- The mandibular nerve enters through the foramen ovale and divides immediately; the otic ganglion lies medial to the nerve, between it and the tensor veli palatini.
- The maxillary artery's second part (pterygoid part) crosses the fossa, superficial or deep to the lateral pterygoid, giving the masticatory muscle branches.
- The middle meningeal artery arises in the fossa and re-enters the cranium through the foramen spinosum in the roof.
- The chorda tympani enters the fossa through the petrotympanic fissure and joins the lingual nerve close below the skull base.
- The pterygoid venous plexus around and between the pterygoids drains to the maxillary vein, and connects through emissary veins with the cavernous sinus.
- The fossa communicates with the pterygopalatine fossa through the pterygomaxillary fissure, and with the temporal fossa deep to the zygomatic arch.
How infection from this fossa reaches the cavernous sinus
A lower molar dental abscess, inadequately drained, spreads into the infratemporal fossa. Follow the route stepwise. The infected material collects around the lateral pterygoid among the venous tributaries of the pterygoid plexus. This valveless network drains backwards to the maxillary vein, but it also sends emissary veins upward through the foramina of the skull base — notably the foramina of Vesalius and ovale — to the cavernous sinus. Retrograde flow carries infection into the sinus, and the patient develops fever, proptosis, chemosis, lid oedema and ophthalmoplegia, with the abducent nerve affected earliest because it lies free within the sinus lumen.
The cavernous sinus anatomy completes the clinical picture: the third, fourth, ophthalmic and maxillary nerves in the lateral wall are involved as the thrombosis advances, and the sight-threatening complications of septic thrombosis demand high-dose intravenous antibiotics per current practice with drainage of the primary dental source. The same fossa also explains mandibular nerve block technique: a needle passed through the sigmoid notch of the mandible, or via the extraoral approach to the foramen ovale, deposits anaesthetic around the mandibular nerve as it enters the fossa; too deep a placement is intracranial, too medial hits the medial pterygoid plate — the fossa's walls guiding the block.
Where students slip
Two structures are misplaced in diagrams. The otic ganglion is drawn "on the parotid gland" because its fibres end there; anatomically it lies in the fossa, medial to the mandibular nerve, and its postganglionic fibres reach the parotid only by hitch-hiking on the auriculotemporal nerve — the position and the route are separate marks. Second, candidates route the chorda tympani "through the foramen ovale"; it enters through the petrotympanic (squamotympanic) fissure, joining the lingual nerve within the fossa. Third, the pterygoid plexus is remembered for epistaxis rather than for its cavernous sinus connection; the examinable statement is that the plexus is the valveless bridge between the face's deep veins and the intracranial sinus, which is also why tumours of the nasopharynx and pterygopalatine region extend intracranially along it.
Frequently asked questions
Which foramina in the roof of the infratemporal fossa transmit its nerves and vessels?
The foramen ovale for the mandibular nerve and the foramen spinosum for the middle meningeal artery, both in the infratemporal surface of the greater wing of the sphenoid.
How does infection from this region reach the cavernous sinus?
Through the valveless pterygoid venous plexus and its emissary veins traversing the skull base foramina.
Where does the chorda tympani join the lingual nerve?
In the infratemporal fossa, near the medial aspect of the lateral pterygoid, after entering through the petrotympanic fissure.
Where is the otic ganglion located?
Medial to the mandibular nerve in the infratemporal fossa, just below the foramen ovale, relay station for the parotid's secretomotor fibres.
With which space does the fossa communicate medially?
The pterygopalatine fossa, through the pterygomaxillary fissure, by which its vessels and nerves continue towards the nose and palate.