Infratemporal Fossa Anatomy

Infratemporal Fossa Overview

• Cavity located inferomedially to the zygomatic arch
• Incomplete encasement in bone
• Anterolateral, inferior wall contains soft tissue mainly comprised of muscle

Borders of the Infratemporal Fossa

• Anterior border consists of infratemporal surface of the maxilla and the anterior ridge of the zygomatic process
• Posterior border, anterior surface of the temporal and sphenoid bones
• Superior border is the greater wing of the sphenoid, located below the infratemporal crest, and the underside of the temporal squama
• Inferior border is the medial pterygoid muscle
• Medial border formed by the lateral pterygoid plate
• Lateral border includes the zygomatic arch and the ramus of the mandible

Muscular Contents of the Infratemporal Fossa

• Temporalis: A muscle of mastication palpable in the temporal region, originates broadly off the temporal squama
• The temporalis passes posterior to the zygomatic arch and inserts on the coronoid process of the mandible
• Contraction of the temporalis elevates and retracts the mandible, closing the jaw
• Innervation of the temporalis is via the temporal branches of the anterior division of V3
• Masseter: A prominent muscle of mastication forming the fleshy mass of the posterior jaw
• The masseter originates off the inferior margin of the zygomatic arch and inserts along the superficial surface of the mandibular ramus
• Contraction of the masseter elevates and protrudes the mandible, closing the jaw
• Innervation of the masseter is via the mandibular branch of the anterior division of V3
• Lateral Pterygoid: A muscle of mastication located deep in the infratemporal fossa, classified as a bicipital muscle
• The superior head of the lateral pterygoid originates off the inferior surface of the greater wing of the sphenoid bone
• The inferior head originates off the lateral pterygoid plate
• Superior and inferior portions of the lateral pterygoid fuse, running laterally to insert on the condyloid process of the mandible
• Contraction of the lateral pterygoid depresses and protrudes the mandible, opening the jaw
• Unilateral contraction results in side-to-side movement during mastication
• Innervation is by the lateral pterygoid branch of the anterior division of V3
• Medial Pterygoid: A thick, quadrangular muscle of mastication deep in the infratemporal fossa, also bicipital
• The deep head of the medial pterygoid originates off the medial surface of the lateral pterygoid plate
• The superficial head originates from the palatine bone
• Deep and superficial portions fuse, running obliquely at an inferolateral angle to insert on the deep surface of the ramus of the mandible, blending with fibers from the masseter inferiorly
• Contraction of the medial pterygoid elevates the mandible, closing the jaw
• Unilateral contraction results in side-to-side movement during mastication
• Innervated by the nerve to the medial pterygoid off the main trunk of V3

Bruxism

• Bruxism is the medical term for teeth grinding, which involves parafunctional activity of the muscles of mastication
• Daytime grinding, or awake bruxism, is attributed to stress and anxiety, while nighttime grinding, or sleep bruxism, is more likely due to sleep disturbances and neurotransmitter abnormalities

Maxillary Artery

• Serves as the primary blood supply to the infratemporal fossa
• It is one of the two terminal branches off the external carotid artery, originating deep in the neck of the mandible, and has three portions

Mandibular (bony) Portion of the Maxillary Artery

• This is the 1st region of the artery
• It courses medially along the inferior border of the lateral pterygoid muscles before branching into the deep auricular and anterior tympanic arteries

Deep Auricular Artery

• Ascends within the parotid gland to supply the temporomandibular joint and the outer surface of the tympanic membrane

Anterior Tympanic Artery

• The anterior tympanic artery passes deep to the temporomandibular joint
• It pierces the petrotympanic fissure, supplying the inner surface of the tympanic membrane

Middle Meningeal Artery

• Ascends superiorly, passing through the foramen spinosum, and courses along the calvarium superficial to the fibrous dura mater
• The middle meningeal artery runs superiorly deep to the pterion to supply meningeal layers
• The pterion is a structural weak point in the temple region, susceptible to fractures, with potential laceration of the middle meningeal artery and resulting epidural bleeds due to the close approximation

Inferior Alveolar Artery

• Descends with the inferior alveolar nerve to enter the mandibular foramen found along the deep surface of the ramus of the mandible
• Gives off the mylohyoid branch to the mylohyoid muscle just before passing into the mandibular foramen
• Supplies blood to the mandibular bone, pulp of inferior teeth, and the mental branch that emerges through the mental foramen to supply the chin

Pterygoid (Muscular) Portion of the Maxillary Artery

• Runs superior and anterior along the surface of the lateral pterygoid muscle, passing between the superior and inferior heads, and includes the masseteric artery

Masseteric Artery

• Vascular supply dedicated to the masseter muscle

Pterygoid Branches

• Vascular supply dedicated to the medial and lateral pterygoid muscles

Deep Temporal Arteries

• Project superiorly, deep to the temporalis muscle, providing the muscle with vascular supply

Buccal Artery

• Supplies the cheek and buccinator muscle

Pterygomaxillary Portion of the Maxillary Artery

• Deep portion found in the pterygopalatine fossa containing the posterior superior alveolar artery

Posterior Superior Alveolar Artery

• Divides into numerous branches that supply the molars, premolars, and the maxillary sinus

Infraorbital Artery

• Passes through the infraorbital foramen under the orbit of the eye
• Provides orbital branches to the ocular muscles, middle and anterior superior alveolar arteries to the upper incisors, and maxillary sinus

Descending Palatine Artery

• Branches into greater and lesser palatine branches to supply the hard and soft palate, respectively

Artery of the Pterygoid Canal (Vidian Artery)

• Passes backward along the pterygoid canal and supplies the upper pharynx, auditory tube, and tympanic membrane

Sphenopalatine Artery

• Terminal branch of the maxillary artery that passes through the sphenopalatine foramen to enter the nasal cavity
• It gives off posterior lateral and septal branches
• Sphenopalatine artery epistaxis (nosebleeds) can be serious and may require surgical ligation

Mandibular Nerve

• Branch of the trigeminal nerve (V3) that exits the cranial vault through the foramen ovale, comprised of both sensory and motor roots from the brainstem
• The main branch passes between the tensor veli palatine and lateral pterygoid muscles

Meningeal Branch of the Mandibular Nerve

• Reenters the skull with the middle meningeal artery through the foramen spinosum
• Provides sensory innervation to the dura mater

Muscular Branches of the Mandibular Nerve

• Supplies the tensor tympani and tensor veli palatini muscles

Anterior Division of the Mandibular Nerve

• The anterior division is one of two major branches of the mandibular nerve, courses within the submandibular mucosa, and includes the masseteric nerve

Masseteric Nerve

• Crosses over the mandibular notch with the masseteric artery and supplies the masseter muscle

Deep Temporal Nerves

• The anterior and posterior branched temporal nerves that run anteriorly into the temporal fossa and supply the temporalis muscle

Buccal Nerve

• Courses under the temporalis tendon to fuse with the buccal branch of the facial nerve
• It provides sensory information from the skin and cheek mucosa

Lateral Pterygoid Nerve

• Supplies the lateral pterygoid muscle

Posterior Division of the Mandibular Nerve

• The posterior division is the second major branch that passes into the mandibular foramen and includes the auriculotemporal nerve

Auriculotemporal Nerve

• Arises as 2 roots that encircle the middle meningeal artery
• Passes posterior to the neck of the mandible, running superiorly, and gives sensory branches to the superficial temporal region and tympanic membrane

Parasympathetic branches

• Parasympathetic branches from CNIX supply the parotid gland
• Frey's syndrome results from this nerve severed during parotidectomy, with severed parasympathetic branches spontaneously coupled with sweat glands in the region, resulting in hyperhidrosis (excessive sweating) while eating

Lingual Nerve

• Courses inferior to the lateral pterygoid muscle, where it accepts the chorda tympani nerve from CNVII
• Passes medially to the ramus of the mandible and becomes embedded in the mucosa along the floor of the mouth
• Receives general somatic sensory innervation from the anterior 2/3rds of the tongue
• Carries special sensation and parasympathetics from the facial nerve for taste & salivation

Inferior Alveolar Nerve

• Passes inferior to the lateral pterygoid muscle to enter the mandibular foramen
• Supplies sensation to the lower teeth, continues through the mental foramen to supply sensation to the chin
• Gives off a nerve to the mylohyoid prior to entering the mandibular foramen and innervates the mylohyoid and anterior belly of the digastric muscle

Pterygopalatine Fossa

• The pterygopalatine Fossa is a cone-shaped depression deep to the infratemporal fossa with boundaries and communications
• Anterior border, the infratemporal surface of the maxilla communicates with the orbit through the inferior orbital tissue
• Posterior border, the pterygoid process and greater wing of the sphenoid bone
• Medial border, the perpendicular plate of the palatine bone communicates with the nasal cavity through the sphenopalatine foramen
• Lateral border, the pterygomaxillary fissure communicates with the lateral portion of the infratemporal fossa, which is an open structure
• Inferior border, the pyramidal process of the palatine bone communicates with the oral cavity through greater and lesser palatine canals

Maxillary Artery

• The terminal portion of the maxillary artery enters the pterygopalatine fossa
• The sphenopalatine artery passes through the sphenopalatine foramen and branches extensively as the nasopalatine artery

Maxillary Nerve

• Passes between the foramen rotundum and infraorbital canal through the superior margin of the pterygopalatine fossa
• Gives off posterior superior alveolar nerve branches, and communicates with the pterygopalatine ganglion

Pterygopalatine Ganglion

• The parasympathetic ganglion is embedded in the pterygopalatine fossa
• A "crossroad" with numerous branches has masses passing through to various destinations

Sensory Root

• Pterygopalatine (sphenopalatine) nerves project inferiorly through the pterygopalatine ganglion from the maxillary nerve (V2) to join greater and lesser palatine nerves
• It terminates in the roof of the mouth and the nasal cavity to receive sensory information

Parasympathetic Root

• The source of post-synaptic cell bodies is a portion of post-synaptic parasympathetic cells from the facial nerve
• Receives pre-synaptic fibers from the greater petrosal branch of the facial nerve through the nervus intermedius
• Post-synaptic fibers project to: Lacrimal gland (fibers through V2,V1 reaches gland)

Sympathetic Root

• Post-ganglionic fibers from the carotid plexus form the deep petrosal nerve
• The deep petrosal nerve fuses with the greater petrosal nerve to form the nervus intermedius, which enters the pterygopalatine ganglion

Symathetic Nerves

• Sympathetic nerves continue through the pterygopalatine ganglion without synapsing, following parasympathetic fibers to the lacrimal, nasal, and oral glands to limit secretions