6.8 Infratemporal Region

Infratemporal Fossa

Under base of skull b/n wall of pharynx and ramus of mandible (aka parapharyngeal space)

 
Boundaries (plate 2)

Medial: lateral plate of pterygoid process, with tensor palati and superior constrictor behind (62)

-           in front of lateral pterygoid plate (b/n it & maxilla) = pterygomaxillary fissure through which infratemporal fossa communicates with pterygopalatine fossa.

Lateral: ramus of mandible and coronoid process

Anterior: posterior surface of maxilla

-           at upper margin = inferior orbital fissure = gap b/n it and greater wing of sphenoid

Roof: medially by infratemporal greater wing & adjacent squamous part of temporal bone

-           sphenoid here is perforated by foramen ovale and spinosum (Pl 5)

-           sphenoid here bounded laterally by infratemporal crest = bone right-angles up to side of skull

-           roof here  = space deep to zygomatic arch where infra & supratemporal fossae communicate

Posterior: styloid process, with carotid sheath behind.

 
Contents

Deep part of parotid gland (19)

Medial and lateral pterygoids (49)

Insertion of temporalis ® coronoid process (48)

Maxillary artery & branches (35); pterygoid venous plexus (64)

Mandibular nerve and branches; otic ganglion; chorda tympani & post sup branches of V (maxillary) (65)

 
Lateral Pterygoid (49)

Arises: 2 heads: upper = roof of fossa (sphenoid); lower = lateral pterygoid plate; these lie edge to edge

Insert: heads converge ® pterygoid fovea on front of mandibular neck

-           upper fibres ® to capsule and articular disk of TMJ

Nerve: anterior division mandibular nerve

Action: draws condyle / disc forwards from mandibular fossa down slope of articular eminence

-           ie indispensable to chewing action; chews with its medial counterpart.

 

Medial Pterygoid (49)

Arises: 2 heads: deep = larger; medial surface of lateral plate; ie deep lat pt.; cf superficial = superficial

-           superficial head (small) from tuberosity of maxilla and pyramidal process of palatine bone

Inserts: parts fuse below margin of lat pterygoid ® down and back to angle of mandible

-           inserts at rough area on medial surface of angle as far as mylohyoid groove (10)

-           tendinous intersections on surface

Nerve: Branch from main trunk mandibular

Action: Pulls upwards, forwards, medially, closing mouth; pulls jaw to its side; chews with fellows

-           if all 4 pterygoids contract together ® jaw protrusion.

 

Maxillary Artery (35)

Enters fossa deep to neck of mandible; b/n neck and sphenomandibular ligament.

-           auriculotemporal nerve above, maxillary vein below

® forward b/n two heads of lat pterygoid; deep into pterygomaxillary fissure ® pterygopalatine fossa.

Described in 3 parts: before, on and beyond lateral pterygoid; 5 branches from each.

-           from 1st and 3rd parts, all branches ® foramina in bones

-           from 2nd part, all ® muscular.

1st part (35)

  1. Inferior alveolar artery meets companion nerve ® nv trunk passes into mandibular foramen; supplies pulps of mandibular teeth and body of mandible

- mental branch emerges from mental foramen ® lip and skin

  1. Middle meningeal artery ® through foramen spinosum (5); meets auriculotemporal n. roots

- a branch is carried by it from SNS otic ganglion

  1. Accessory meningeal ® through foramen ovale (5) ® dura mater or floor of middle fossa and trigeminal cave; supplies trigeminal ganglion
  2. Deep auricular ® ear (more superficial) ® EAM b/n cartilage and bone
  3. Anterior tympanic ® through petrotympanic fissure (5) ® middle ear ® anastomosis around tympanic membrane

2nd part

Branches to soft tissues: pterygoid muscles and deep temporal branches ® temporalis

-           also branches ® accompanying lingual & buccal nerves. 

3rd part

In pterygopalatine fossa, branches all accompany nerves via foramina

-           then passes forward with maxillary nerve ® inferior orbital fissure as small infraorbital artery, which emerges with infraorbital nerve from infraorbital canal.

  1. Sphenopalatine artery: through sphenopalatine foramen ® nasal cavity (main artery 36)
  1. Posterior sup alveolar artery: with nerves ® foramina in posterior wall of maxilla (35)
  2. Greater palatine: ® through greater palatine foramen ® hard palate 36; also gives lesser palatine artery ® through the lesser palatine foramen.
  3. Pharyngeal artery: enters palatovaginal canal (35)
  4. Artery of pterygoid canal: through own canal (35)
 
Posterior Superior Alveolar Nerve (40)

From maxillary nerve ® off in pterygopalatine fossa ® 2-3 branches, pierce posterior maxilla wall separates ® molar teeth and mm of maxillary sinus

-           another branch ® along alveolar margin of maxilla to 1st molar tooth ® gingiva

-           can be blocked here by infection through vestibule of mouth (pterygoid plexus may bleed)

 

Pterygoid Plexus (64)

Very small veins in and around lateral pterygoid muscle

-           tributaries correspond to branches of maxillary artery; do not return all arterial blood; has other routes eg facial veins, pharyngeal veins, diploic veins.

Does drain inferior ophthalmic vein via inferior orbital fissure and deep fascial vein

® empties into maxillary veins ® joins superficial temporal ® retromandibular vein

Valved, aids return by pumping of lateral pterygoid.

Emissary veins connect with cavernous sinus via foramen ovale and lacerum.

 

Sphenomandibular Ligament (35)

Flat band of tough fibrous tissue from narrow attachment of spine of sphenoid.

-           broadens downwards ® lingula and inferior margin of mandibular foramen

-           derived from perichondrium of Meckel’s cartilage

-           auriculotemporal nerve and maxillary vessels b/n it and neck of mandible

-           b/n it and ramus of mandible are inferior alveolar vessels and nerve

Rest of space b/n ligament and mandible = parotid gland

Pierced by mylohyoid nerve (branch of inferior alveolar) and accompanying vessels

Mandibular Nerve (41)

From trigeminal ganglion; on dura of middle cranial fossa lateral to cavernous sinus.

-           with motor root of V ® enters foramen ovale; two join ® emerge as mandibular nerve

-           lies deep to upper head of lateral pterygoid (b/n it and tensor palati

-           otic ganglion lies on its deep surface (cf pterygopalatine ganglion on maxillary nerve)

Short course then ® small anterior (mainly motor) and large posterior (mainly sensory) branches

 
Main Trunk Branches

One sensory, one motor.

Meningeal branch (nervus spinosus) ® re-enters middle cranial fossa via foramen spinosum with the meningeal artery (or ovale)

® meninges of middle cranial fossa and mastoid air cells.

N. to medial pterygoid ® runs forward to its muscle ® branch through otic ganglion ® two tensors

 
Anterior Division Branches

Motor, except for one branch (buccal)

Deep temporal: 2. ® temporalis passing by upper border of lateral pterygoid

Masseteric: same course ® emerges through mandibular notch into deep surface of muscle

-           also gives a branch to TMJ

N to lat pterygoid: run s with buccal ® both heads

-           note the motor branch of 5 supplies all the chewing muscles (med pterygoid from main)

Buccal: emerges b/n two heads of lat pterygoid ® down over buccinator ® skin of cheek

-           then pierces buccinator (proprioceptive) ® mm of cheek, gum, lower jaw to mental foramen.

 

Posterior Division Branches

Sensory, except for one branch (mylohyoid nerve).

3 branches.

Auriculotemporal: from two roots; embracing middle meningeal artery

-           passes back b/n neck of mandible and sphenomandibular lig above maxillary vessels

-           ® TMJ jt, and ascends over lateral zygomatic arch behind superficial temporal vessels

-           auricular part ® skin of tragus and upper pinna, EAM and outer tympanic membrane

-           temporal via skin of temple; in contact with anteromedial parotid ® supplies the gland with postganglionic secretomotor fibres from otic ganglion.

-           Note on pl 18 how mandibular nerve is distributed.

 

Inferior alveolar nerve: emerges below lower head of lat pterygoid ® curves down on med pterygoid.

-           ® anterior to its vessels b/n ramus mandible & sphenomandibular lig (ie close to bone) ® mandibular foramen

-           here = site of inferior alveolar nerve block.

-           mylohyoid nerve leaves the inferior alveolar at a foramen high in ramus ® pierces sphenomandibular ligament ® lies on groove on mandible above med pterygoid insertion with vascular branches; then ® on superficial mylohyoid (& ant belly digastric).

-           The inferior alveolar nerve and vessels run in mandibular canal; ® 3 molars + 2 premolars

-           Then divides ® mental nerve and incisive nerve; latter ® canines & both incisors.

 

Lingual nerve: appears below lat pterygoid ® down on medial pterygoid ® adjacent to mandible by third molar.

-           groove here separates pterygomandibular raphe above and mylohyoid below

-           ® enters mouth on superior surface mylohyoid here ® gingival branch ® lingual gum and mucous membrane of floor of mouth.

-           Lingual nerve then crosses submandibular duct ® forwards & medially to tongue.

 

Chorda Tympani: from facial nerve

-           ® through petrotympanic fissure ® grooves medial spine of sphenoid & joins lingual acutely.

-            Distributed with lingual to anterior 2/3 of tongue; also PNS secretomotor to submandibular ganglion, and taste from anterior 2/3 tongue.

 

Otic Ganglion (41)

Small.  B/n tensor palati and mandibular nerve, just below foramen ovale.

2-3cm, flat against medial surface of nerve.

Relay for PNS secretomotor to parotid (lesser petrosal branch of IX brings these fibres)

Postganglionic SNS from plexus around middle meningeal, sensory from auriculotemporal and a branch from nerve to medial pterygoid pass through the ganglion without relay.

 

Carotid Sheath & Cranial Nerves

Carotid Sheath (28-29)

From base of skull ® arch of aorta.  Upper part = attached to margins of carotid canal, jugular fossa.

-           contains here: ICA, IJV, and CNs IX – XII

-           medial = pharynx, laterally = parotid (deepest part); with styloid process and three muscles b/n.

-           anteriorly = infratemporal fossa; behind = cervical sympathetic trunk on prevertebral fascia.

Carotid canal lies immediately in front of jugular foramen (deep to EAM); hypoglossal canal is more medial between.

-           IJV is behind, at skull base, but slopes in descent & is lateral to CCA on scalenus anterior

-           Vagus is deep in groove b/n the two (in sheath) at all levels.

-           IX and XI emerge b/n artery and vein, then curve away superficial to vessels.

-           XII emerges from its canal medial to sheath, passes through it behind inferior vagal ganglion ® passes forward to emerge between artery and vein

 
IX (65)

Emerges from anterior part of jugular foramen on lateral side of inferior petrosal sinus.

-           deeply notches inferior border of petrous bone; inferior ganglion here bulges nerve

-           this ganglion contains cell bodies of sensory fibres in the nerve

Then passes down on internal carotid ® curves forward around lateral stylopharyngeus (see 63 – passes between internal and external carotids)

Passes deep to posterior border of hyoglossus to reach tongue.

Tympanic branch

Leaves nerve at jugular fossa ® through a canaliculus on ridge of petrous bone b/n carotid & jugular foramen ® enters temporal bone ® middle ear, mastoid air cells, bony part of auditory tube.

-           With this branch are also fibres from the inferior salivary nucleus ® through tympanic plexus ® lesser petrosal ® leaves middle ear through its roof ® along floor of middle cranial fossa ® exits via foramen ovale ®  otic ganglion; PNS relay ® secretomotor to parotid, mouth.

Motor branch

To stylopharyngeus; given where nerve meets that muscle: NB IX is NOT wholly sensory.

Carotid sinus nerve

Main supply to carotid sinus and carotid body (chemo, baroreceptors)

Pharyngeal branches

Join pharyngeal plexus on middle constrictor ® pierces it ® mm of oropharynx (sensation and taste)

Tonsillar branch

® mm of tonsil

Lingual

® posterior 1/3 of tongue with sensory fibres (sensation & taste) & secretomotor to glands of post 1/3.

Relay in small ganglia in mucous membrane

 
X (120)

Emerges through middle compartment of jugular foramen; small enlargement here = superior ganglion.

Below skull base, inferior ganglion dilates the trunk.

-           ganglia = cell bodies of afferent fibres; superior = meningeal & auricular; inferior = all else

-           inferior met by large branch from XI = nucleus ambiguus fibres of head / neck skeletal muscles

Runs straight down neck in carotid sheath; b/n & behind carotid artery and jugular vein

-           in root of neck passes in front of subclavian artery (220), enters mediastinum ® viscera

Meningeal branches: up from superior ganglia ® dura mater of posterior fossa below tentorium.

Auricular: runs laterally through a canaliculus in lateral wall jugular fossa ® tympanic membrane (posteroinferior), EAM and some of cranial auricular surface

Carotid body branch: plexus with carotid sinus branch of IX for supply of those structures.

Pharyngeal branch: b/n internal & ext carotids ® pharyngeal plexus on middle constrictor.

 ® muscles of pharynx (except stylopharyngeus = IX) and muscles of soft palate (except tensor palati)

Superior laryngeal nerve (69): from side wall of pharynx ® large internal laryngeal (to piriform recess carrying sensation for larynx & pharynx; and small external laryngeal (runs close to superior thyroid vessels, outside larynx ® cricothyroid and inferior constrictor.

Cervical cardiac branches: two per side ® cardiac plexus (except for left lower ® superficial plexus)

Recurrent laryngeals: right ® around subclavian; left ® anterior to ligamentum arteriosum

-           both have cardiac branches; also supply trachea, oesophagus, cricopharyngeus, before ® pharynx and larynx to laryngeal muscles (except cricothyroid) and laryngeal mucosa from folds down.

 

XI (121)

Formed in posterior canal from union of cranial and spinal roots.

-           lives in middle compartment in jugular foramen; lateral to vagus, shares a meningeal sleeve

-           - note IX,X,XI all exit via jugular foramen, with inferior petrosal sinus, sigmoid sinus and posterior meningeal artery.

All cranial root fibres ® join vagus; to supply all the all muscles of larynx via laryngeals apart from cricothyroid); cervical fibres run down and back on IJV

-           passes deep to styloid and posterior digastric, crossed by occipital artery.

With upper SCM branch of occipital, reaches SCM, supplies it; enters deep surface

-           emerges from posterior border, then crosses posterior triangle ® trapezius.

 

XII (122)

Emerges from hypoglossal canal.  Picks up anterior ramus C1, spirals behind inferior ganglion of vagus ® emerges b/n internal carotid and IJV, then descends on the carotid sheath.

Crossed by occipital artery and its lower SCM branch, then turns forward superficial to lingual artery.

-           just above tip of greater horn of hyoid

-           continues forward on hyoglossus with veins draining tip of tongue; ® tongue muscles.

C1 fibres joining hypoglossal leave it progressively in the superior root of ansa cervicalis and in branches to thyrohyoid and geniohyoid.  Small meningeal branch also comprises C1 fibres.

Styloid Apparatus

Styloid Process = part of temporal bone; from its tip stylohyoid ligament passes to lesser horn of hyoid.

-           both process and ligament = remnants of 2nd pharyngeal arch cartilage; variable in length

Three muscles diverge from it: Stylopharyngeus (IX) highest from medial side of base ® larynx

-           Stylohyoid (VII) arises posteriorly near base

-           Styloglossus (XII) from low down in front and upper ligament

-           These two diverge as they pass down and forward to hyoid bone & side of tongue.

-           Each has a different nerve supply, all act significantly during swallowing.

Styloid apparatus lies lateral to carotid sheath

External carotid passes b/n muscles of stylohyoid apparatus

-           runs deep to digastric and stylohyoid, but superficial to stylopharyngeus

Retromandibular vein, meanwhile, runs down from parotid superficial to stylohyoid and digastric.