Content Reviewers:Viviana Popa, MD, Andrew Horne, MSc, BSc (Hons), Leah Labranche, PhD, MSc, BSc(Hons)
The infratemporal fossa, or IT fossa for short, is one of the most important spaces in the head, which acts as a conduit for neurovascular structures entering and exiting the cranial cavity. It contains vital structures such as the maxillary artery and mandibular nerve.
The infratemporal fossa is an irregularly shaped space located deep and inferior to the zygomatic arch, deep to the ramus of the mandible, and posterior to the maxilla.
More specifically, the fossa is bounded laterally by the the ramus of the mandible; medially by the lateral pterygoid plate; anteriorly by the posterior surface of the maxilla; posteriorly by the tympanic plate and the temporal bone’s mastoid and styloid processes; superiorly by the inferior surface of the greater wing of the sphenoid, and inferiorly by the attachment of the medial pterygoid muscle close to the angle of the mandible.
Now, the important structures within the infratemporal fossa include muscles, vessels and nerves.
Within the infratemporal fossa we also see the chorda tympani nerve, which is actually a branch or cranial nerve seven.
Now let’s take a more in depth look at the different structures within the infratemporal fossa, starting with the vessels.
First up, the maxillary artery! This artery branches off from the external carotid artery, posterior to the neck of the mandible.
Then, it courses either deep to or on the superficial surface of the lateral pterygoid muscle, until it reaches the pterygomaxillary fissure. From here onward, the maxillary artery continues as the sphenopalatine artery.
Simple, right? Well, actually, this artery gives off no less than 15 branches along its course of the infratemporal fossa.
Let’s quickly run through six of the most important ones. First, the artery originates within the mass of the lateral pterygoid muscle, moves laterally and passes through the mandibular notch to enter the deep surface of the masseter muscle, which it supplies.
Fourth, there’s the posterior superior alveolar artery, just anterior to the lateral pterygoid.
This artery branches off the maxillary artery as it enters the pterygomaxillary fissure, and enters the infratemporal surface of the maxilla via the alveolar foramen.
Fifth, there’s the middle meningeal artery, deep to the lateral pterygoid muscle. It arises medial to the neck of the mandible, and then moves upwards, passing through a split in the auriculotemporal nerve.
Finally, there’s the inferior alveolar artery which begins its descent through the infratemporal fossa alongside the inferior alveolar nerve to enter the mandibular canal to supply the mandibular teeth, the mandible, mylohyoid muscle and the skin in the chin region.
The last vascular structure within the infratemporal fossa is the pterygoid venous plexus.
This venous plexus is located between the temporalis and pterygoid muscles and it surrounds the maxillary artery.
This way, the tributaries of the venous plexus parallel the branches of the maxillary artery. Something to keep in mind about this plexus is its multiple routes of drainage.
This is important to understand because infections of the infratemporal fossa can spread to the cranial cavity this way.
Time for a quick break! Can you recall six important branches of the maxillary artery?
Great! Now let’s switch gears and take a closer look at the nerves in the infratemporal fossa.
The mandibular nerve arises from the trigeminal ganglion in the middle cranial fossa, and here it receives the motor root of the trigeminal nerve.
Then, it descends through the foramen ovale in the greater wing of the sphenoid and into the infratemporal fossa deep to the lateral pterygoid muscle.