Infratemporal fossa and TMJ

• What is the infratemporal fossa?

  •‘Space’ beneath the base of the skull - between the skull and the ramus of the mandible

  It is the area that the foramen ovale opens into, which allows the mandibular branch of the trigeminal nerve to exit the skull. The middle meningeal artery passes from the infratemporal fossa into the foramen spinosum to gain entry into the skull.

  
• Boundaries

  •Anterior = posterior surface of the maxilla

  •Posterior = styloid process

  •Superior = infratemporal surface of the greater wing of sphenoid

  •Medial = lateral pterygoid plate

  •Lateral = ramus of the mandible

  Terminal branches of the maxillary artery pass through the pterygomaxillary fissure to exit the infratemporal fossa.

  
• Contents of the ITF

  •Lateral and medial pterygoid

  •Mandibular division of trigeminal and branches

  •Maxillary artery and branches

  •Pterygoid venous plexus

  •Chorda tympani

  •Otic ganglion
• Medial and lateral pterygoid re-cap

  •Medial pterygoid = assists in elevating the mandible

  •Lateral pterygoid = pulls the neck of the mandible forward

  •Together chewing movements

  •Mandibular division of CN V

  
• Mandibular division of trigeminal nerve

  •Anterior division = x2 deep temporal, masseteric, n. to lateral pterygoid, buccal (buccal = sensory)

  •Posterior division = lingual (joined by chorda tympani), inferior alveolar, mylohyoid, auriculotemporal

  •Pre-division = meningeal branch, nerve to medial pterygoid and communicating branch (tensor tympani and tensor veli palatini)

  
• Mandibular division of trigeminal nerve

  The mandibular division of the trigeminal nerve passes through the foramen ovale and into the infratemporal fossa. The inferior alveolar branch supplies the lower teeth and then passes out onto the face to supply cutaneous innervation to the skin over the mandible. The auriculotemporal branch supplies cutaneous innervation to the skin anterior to the auricle. Other branches formed in the infratemporal fossa supply small muscles found in the ear and in the soft palate.

  
• The inferior alveolar and lingual nerves are the largest branches formed.

  
• Maxillary artery

  •Deep temporal, masseteric and pterygoid branches to muscles

  •Maxillary artery passes between 2 heads of lateral pterygoid to go into pterygomaxillary fissure/ fossa and give off posterior superior alveolar branch

  
• Maxillary artery

  The maxillary artery is a terminal branch of the external carotid artery. It passes through the infratemporal fossa where it branches to form arteries that supply the muscles of mastication, the dura, the lower teeth and the cheek. It then passes between the heads of lateral pterygoid to send branches to the upper teeth.

  
• the artery

  
• •3 parts = mandibular (green), pterygoid (yellow) and pterygopalatine (blue)

  •Pterygopalatine branches=

  •Posterior superior alveolar (upper molar and premolar)

  •Infraorbital (canal in floor of orbit, foramen)

  •Anterior superior alveolar branches (upper incisor and canine)

  •Palatine, pharyngeal and sphenopalatine branches

  
• Pterygoid venous plexus

  •Surrounds lateral pterygoid

  •Veins from orbit, nasal and oral cavities

  •Communicates with cavernous sinus and facial vein (areas supplied by maxillary artery)

  •Drained by maxillary vein

  •Route for infection

  The pterygoid venous plexus communicates with the cavernous sinus inside the skull and the facial vein that drains the superficial structures of the face.

  
• Chorda tympani

  The parasympathetic secretomotor nerves that supplies the submandibular and sublingual salivary glands are from the facial nerve. The main part of the facial nerve passes through the stylomastoid foramen and through the parotid gland to the muscles of facial expression. This is a superficial pathway and does not reach the oral cavity. The lingual branch of the mandibular division of the trigeminal nerve passes from the infratemporal fossa into the oral cavity.

  
• Chorda tympani

  The facial nerve forms a branch called the chorda tympani as it passes through the temporal bone. This branch crosses the handle of the malleus and then passes through a bony canal to reach the infratemporal fossa. There it joins the lingual nerve and the parasympathetic nerves run with the lingual nerve into the oral cavity.

  
• shows the chorda tympani in the infratemporal fossa

  
• Otic ganglion

  Also through otic ganglion (no synapse) = postganglionic sympathetic fibres, and motor nerves to tensor tympani and tensor veli palatini (CNV3)

  This small structure lies at the mouth of the foramen ovale.

  
• TMJ – temporomandibular joint

  -Synovial joint between head of mandible and mandibular fossa & articular tubercle on the squamous part of the temporal bone

  -Articular surfaces fibrocartilage (membranous ossification)

  -Fibrous capsule

  -Nerve supply auriculotemporal and masseteric

  
• TMJ

  •Capsule reinforced by lateral (temporomandibular) ligament

  •Sphenomandibular and stylomandibular ligaments (medially)

  
• Once the capsule is removed the articular tubercle sitting medially

  
• Simple hinge movements can take place between the head of the mandible and the mandibular fossa/disc. To permit the mouth to open more fully, the head of the mandible is pulled forwards towards the articular tubercle by lateral pterygoid. To close the mouth the opposite action must occur using the posterior fibres of temporalis. The articular disc divides the cavity, and increases the congruency of the articular surfaces allowing a bigger, smoother movement.

  
• •Cavity divided by fibrous articular disc

  •Disc increases congruity of articular surfaces

  •Head of mandible and disc = elevation and depression (hinge)

  •Disc and mandibular fossa & articular process = protrusion and retraction (gliding)

  The purple colour is the articular cartilage, the blue shape is the disc and the yellow area indicates the surrounding synovial capsule.

  
• •To close mouth = elevation and retraction pull condyle backwards

  •To open mouth = both sides depression and protrusion to slide disc and condyle forwards towards tubercle

  •Asynchronous gliding = chewing

  
• Movements of the mandible

  •Elevation  = head of mandible and disc move backward and head rotates on lower surface of disc – temporalis, masseter and medial pterygoid

  •Depression = head of mandible rotates on undersurface of articular disc and mandible is pulled forward - lateral pterygoid, digastric, geniohyoid, mylohyoid, gravity

  •Protrusion = articular disc and head of mandible move forward. Movement in upper part of cavity - lateral pterygoid (medial pterygoid assists)
• Movements of the mandible

  •Retrusion = articular disc and head of mandible pulled backward into mandibular fossa – posterior fibres of temporalis

  •Lateral chewing = protrusion and retrusion combined - pterygoids