M01.02.006 The Infra-temporal Fossa

The infratemporal fossa is a complex area located at the base of the skull, deep to the masseter muscle. It is closely associated with both the temporal and pterygopalatine fossae and acts as a conduit for neurovascular structures entering and leaving the cranial cavity. This article explores the anatomy of the infratemporal fossa, detailing its borders, contents, and clinical correlations.

Borders

The infratemporal fossa is wedge-shaped and located deep to the masseter muscle and zygomatic arch. It is closely associated with the pterygopalatine fossa via the pterygomaxillary fissure and communicates with the temporal fossa, which lies superiorly.

Boundaries

• Lateral: Condylar process and ramus of the mandible bone.
• Medial: Lateral pterygoid plate; tensor veli palatine, levator veli palatine, and superior constrictor muscles.
• Anterior: Posterior border of the maxillary sinus.
• Posterior: Carotid sheath.
• Roof: Greater wing of the sphenoid bone.
• Floor: Medial pterygoid muscle.

The roof of the infratemporal fossa, formed by the greater wing of the sphenoid bone, provides an important passage for neurovascular structures transmitted through the foramen ovale and spinosum. Among these are the mandibular branch of the trigeminal nerve and the middle meningeal artery.

Contents

The infratemporal fossa acts as a pathway for neurovascular structures passing to and from the cranial cavity, pterygopalatine fossa, and temporal fossa. It also contains some of the muscles of mastication. The lateral pterygoid splits the fossa contents in half: the branches of the mandibular nerve lay deep into the muscle, while the maxillary artery is superficial to it.

Muscles

The infratemporal fossa is associated with the muscles of mastication. The medial and lateral pterygoids are located within the fossa itself, while the masseter and temporalis muscles insert and originate into the borders of the fossa.

Nerves

The infratemporal fossa forms an important passage for several nerves originating in the cranial cavity:

• Mandibular Nerve: A branch of the trigeminal nerve (CN V). It enters the fossa via the foramen ovale, giving rise to motor and sensory branches. The sensory branches continue inferiorly to provide innervation to some cutaneous structures of the face.
• Auriculotemporal, Buccal, Lingual, and Inferior Alveolar Nerves: Sensory branches of the trigeminal nerve.
• Chorda Tympani: A branch of the facial nerve (CN VII). It follows the anatomical course of the lingual nerve and provides taste innervation to the anterior two-thirds of the tongue.
• Otic Ganglion: A parasympathetic collection of neuron cell bodies. Nerve fibers leave this ganglion ‘hitchhike’ along the auriculotemporal nerve to reach the parotid gland.

Vasculature

The infratemporal fossa contains several vascular structures:

• Maxillary Artery: The terminal branch of the external carotid artery. It travels through the infratemporal fossa.
• Middle Meningeal Artery: Arises within the fossa and passes through the superior border via the foramen spinosum.
• Pterygoid Venous Plexus: Drains the eye and is directly connected to the cavernous sinus, providing a potential route for facial infections to spread intracranially.
• Maxillary Vein
• Middle Meningeal Vein

Clinical Relevance

Fractures of the Pterion

The pterion is the point where the temporal, parietal, frontal, and sphenoid bones meet and the skull is at its weakest. Trauma in this region can lead to an extradural hematoma as the middle meningeal artery (MMA) lies deep into it. An extradural hematoma causes a dangerous increase in intracranial pressure, potentially leading to herniation of brain tissue and ischemia.

Symptoms and Treatment

The increase in intracranial pressure causes a variety of symptoms such as nausea, vomiting, seizures, bradycardia, and limb weakness. It is treated with diuretics in minor cases and drilling burr holes into the skull in more extreme hemorrhages.

Points to Remember

• Location: Base of the skull, deep to the masseter muscle.
• Associated Regions: Temporal and pterygopalatine fossae.
• Borders:
  • Lateral: Condylar process and ramus of the mandible bone.
  • Medial: Lateral pterygoid plate; tensor veli palatine, levator veli palatine, and superior constrictor muscles.
  • Anterior: Posterior border of the maxillary sinus.
  • Posterior: Carotid sheath.
  • Roof: Greater wing of the sphenoid bone.
  • Floor: Medial pterygoid muscle.
• Contents:
  • Muscles: Medial and lateral pterygoids, masseter, and temporalis.
  • Nerves: Mandibular nerve, auriculotemporal, buccal, lingual, and inferior alveolar nerves, chorda tympani, and otic ganglion.
  • Vasculature: Maxillary artery, middle meningeal artery, pterygoid venous plexus, maxillary vein, and middle meningeal vein.
• Clinical Relevance: Fractures of the pterion and potential extradural hematoma.

Bibliography

1. Gray, H. (1918). Anatomy of the Human Body. Philadelphia: Lea & Febiger.
2. TeachMeSeries Ltd (2024). “The Infratemporal Fossa.” TeachMeAnatomy. Available at: TeachMeAnatomy.
3. Wikimedia Commons (2024). “Images and illustrations related to the Infratemporal Fossa.” Wikimedia Commons. Available at: Wikimedia Commons.