Anatomy - Cranial nerves Flashcards
LOCATION OF CRANIAL NERVE NUCLEI
III - VI
III - Midbrain (superior colliculus)
IV - Midbrain (inferior colliculus)
V -
- Motor- upper pons
- Mesencepalic- entire length of midbrain
- Main sensory- upper pons (lateral to motor)
- Spinal- lower pons, medulla to C3
VI - Lower pons
LOCATION OF CRANIAL NERVE NUCLEI
VII - XII
VII - Pontomedullary junction
VIII - Lateral medulla (encroaching on pons)
IX - Medulla (and lowest part of pons)
X - Upper part of medulla
- Branchial motor- nucleus ambiguus
- Visceral efferent- dorsal motor nucleus of the vagus
- Visceral afferent- nucleus of the tractus solitarius
XI -
- Cranial root- nucleus ambiguus (medulla)
- Spinal root- ‘spinal accessory nucleus’ ant horn of C1-6 (esp 2-4)
XII - Medulla
CRANIAL NERVES
NERVE FIBRE TYPES - Branchiomotor
CRANIAL NERVES
NERVE FIBRE TYPES - Somatic sensory
CRANIAL NERVES
NERVE FIBRE TYPES - Visceral Motor (PNS)
CRANIAL NERVES
NERVE FIBRE TYPES - Somatic Motor
(I.e. muscles Not from branchial arches)
CRANIAL NERVES
NERVE FIBRE TYPES - Sensory
(General and Special visceral)
CRANIAL NERVES
NERVE FIBRE TYPES - Special senses
CRANIAL NERVES
NUCLEI - Location in brain stem
Lingual Nerve
Course (& relations in infratemporal fossa)
Cranial Nerve parasympathetic pathways
Lacrimal gland
Lacrimal gland:
Superior salivary nucleus (pons) —> nervus intermedius with CN VII —> geniculate ganglion —> leaves gg via GSPN (facial hiatus) —> MCF —> becomes Vidian nerve @ pterygoid/vidian canal —> pterygopalatine ganglion —> post-ganglionic fibres —> travels through IOF zygomatic nerve (V2) —> communicating branch —> lacrimal nerve of V1 —> Lacrimal gland
Cranial Nerve parasympathetic pathways
Nasal
Nasal:
Superior salivary nucleus (pons) —> nervus intermedius with CN VII —> geniculate ganglion —> leaves gg via GSPN (facial hiatus) —> MCF —> becomes Vidian nerve @ pterygoid/vidian canal —> pterygopalatine ganglion —> post-ganglionic fibres —> distribute to nasal cavity via: PSAN, PIAN, nasopalatine, greater palatine nerves (check these branches)
Cranial Nerve parasympathetic pathways
Partoid gland
Parotid gland:
Inferior salivary nucleus (pons) —> glossopharyngeal nerve —> tympanic branch /Jacobsen (via inf tympanic canaliculus) —> tympanic plexus —> LSPN (via hiatus for LSPN into MCF)—> infratemporal fossa via FO —> otic ganglion —> post-ganglionic fibres —> auriculotemporal nerve (V3) —> Parotid
Cranial Nerve parasympathetic pathways
SMG & sublingual glands
Superior salivary nucleus (? pons) —> nervus intermedius with CN VII—> chorda tympani —> petrotympanic fissure —> infratemporal fossa —> lingual nerve —> submandibular ganglion —> post-ganglionic fibres —> lingual nerve —> SMG/SLG
Cranial Nerve parasympathetic pathways
Sphincter pupillae and ciliaris muscles
Sphincter pupillae and ciliaris muscles
Edinger-Westphal nucleus (parasympathetic motor nucleus associated with the oculomotor nucleus in the brainstem)
—> occulomotor (CN III) —> lateral wall of the cavernous sinus —> SOF —> divides into branches that innervate the LPS and extraocular muscles, but parasympathetic fibers run in the inferior division CN III —> two short “motor roots” synapse in the ciliary ganglion —> short ciliary nerves (x6-10) —> posterior aspect of the eyeball —> sphincter pupillae and ciliaris muscles
Sphincter pupillae = constricts the iris
Ciliaris muscle = changes the shape of the lens (accommodation)
CN III
Nucleus
Nucleus in midbrain at level of superior colliculus (floor of aqueduct)
- Somatic - motor to striated ocular muscles
- Visceral - motor to smooth muscle of eye
Edinger-Westphal Nucleus (cranial to somatic nucleus)
CN III
Course
Course
Passes forward on medial surface of cerebral peduncle
Between PCA and sup cerebellar arteries, then below/lat to P Comm A
Pierces arachnoid/dura on roof of cavernous sinus
Lateral wall of cavernous sinus, above VI, slants medial to IV and V1
Picks up SNS fibres from ICA (to sympathetic part of LPS)
Anterior end of cavernous sinus (oculomotor foramen) - splits to superior and inferior divisions
Passes through SOF within tendinous ring
Superior division - SR and LPS
Inferior division - 3 branches
- MR
- IR
- Longer nerve to IO
- Contains the PSNS Edinger-Westphal fibres. Leave it to enter ciliary ganglion. Short ciliary nerves then supply sphincter pupillae and ciliary muscle (accommodation)
CN III
Palsy
Down & Out
CN IV
Nucleus
Nucleus: Midbrain at level of inferior colliculus
CN IV
Course
Nerve emerges dorsally (the only nerve to exit on dorsal surface)
Runs between PCA and Sup Cerebellar A (lateral. III is medial)
Directed to roof of cavernous sinus where it pierces dura/arachnoid
Runs forward in cavernous sinus below III (III then crosses IV medially, making IV the uppermost nerve at the anterior end of the sinus)
Enters SOF outside of tendinous ring
Passes over LPS to enter orbital surface of SO (1/3 along the muscle)
CN IV
Action & Testing
Superior Oblique action depends on position of eye
Internal rotation, depression, abduction
If acting in isolation —> turns eye down and out (same finding with CN III palsy)
To test the muscle ask the patient to look down and in (this removes LR and IR and tests SO alone)
CN V
Nucleus
Nuclei:
Motor - upper pons, 1st branchial arch
3 parts of the sensory nucleus, spans length of brainstem
- Mesencephalic - length of midbrain, proprioceptive
- Main sensory - upper pons lateral to motor nucleus, touch
- Spinal - lower pons to medulla and through to C3, pain and temp
CN V
Course
Motor root emerges above/medial to sensory root
Runs forward underneath the tentorium cerebellum
Pass forward to Meckel’s cave- tubular prolongation of arachnoid-lined fibrous dura (passes from PCF to MCF across petrous apex)
Sensory part then expands as the trigeminal ganglion (motor part separate)
NOTE: the proprioceptive fibres destined for mesencephalic nucleus pass through without synapse
Dura fuses with pia 1/2 way along ganglion. Thus ant 1/2 has no CSF - sensory roots are given off here
V1 and V2 pass anteriorly to cavernous sinus
V3 joins the motor root and passes through FO
CN - V1
Course & Branches
Runs on Lateral wall of cavernous sinus
Within the Cavernous Sinus
- Picks up SNS fibres to dilator pupillae
- Gives of Tentorial Nerves (meningeal)
3 branches after that:
Lacrimal
Frontal
Nasociliary
Lacrimal Nerve
Course & Action
Br V1
Exits cavernous sinus
Passes lateral to tendinous ring in SOF
Picks up secretomotor fibres from Zygomatic N to lacrimal gland
- These fibres are from the Geniculate Ganglion via GSPN, Vidian Nerve and relay without synapse through the PPG to the Zygomatic nerve
Sensation to lateral eyelid
Frontal Nerve
Course and Action
Frontal
Through SOF, lateral to tendinous ring, runs above LPS, then divides to:
Supraorbital - frontal sinus, forehead and upper eyelid (lateral)
Supratrochlear - narrow midline strip of forehead, upper lid conjunctiva
Nasociliary / Anterior Ethmoid Nerve
Course & action
Nasociliary
Changes name twice - AE Nerve, Ext Nasal N
Within tendinous ring, between Sup and Inf divisions of III
passes along med orbital wall, below SO, enters ant ethmoid foramen (becomes the (Anterior Ethmoid Nerve)
Then crosses roof of nose lat-med, post-ant and passes on cribriform plate (i.e. within ACF)
Descends through slit alongside crista galli to roof of nose
Now the External Nasal N (exits nose between nasal bones and ULC) - supplies nasal dorsum down to tip
- Involvement of this branch in zoster suggests involvement of ciliary nerves and thus cornea- risk of damage due to loss of corneal sensation
V2 - Maxillary Nerve
Course & Action
Runs in lateral wall of cavernous sinus below V1
Passes through Foramen Rotundum to PPF
Short course (lateral) to IO Fissue then changes its name when enters IO canal to Infraorbital N
Branches
- Middle Meningeal N - ant 1/2 of MCF
- Ganglionic branch - V2 —> PPG —> Branches of ganglion (x6, see next facet)
- Posterior Superior Alveolar N
- Zygomatic N
- arises in PPF,through IO Fissue, along lower/lat wall of orbit
- Post-ganglionic fibres to lacrimal gland (via Lacrimal N)
- Divides in the Zygomatic bone
- Zygomaticotemporal- hairless skin over temple
- Zygomaticofacial- skin over zygomatic bone
V2 - infraorbital branch
Course & Action
Infraorbital N, branches
- Middle Sup Alveolar N - max sinus, 2 premolars, ant/buccal root of 1st molar
- Ant Sup Alveolar N - max sinus, canine, 2 incisors, ant/inf LNW + floor of nose
- exits IO foramen onto ant maxilla (palpebral- to lower lid + conjunctiva, nasal- strip of ext nasal skin, labial- upper lip and gum)
Pterygopalatine ganglion Branches
Branches of the Pterygopalatine Ganglion:
- parasympathetic root from GSPN
- sympathetic root from deep petrosal nerve
together for vidian nerve
- sensory root via V2
1. Nasopalatine N - SP foramen - Septum + incisive gum of hard palate
2. Lat Post Sup Nasal Ns- SP foramen - Postersup quadrant of LNW
3. Greater Palatine N - GP foramen/canal (junction of maxilla and palatine bone) - Mucosa of hard palate
- Nasal branches- posteroinf quadrant LNW + med wall max sinus
4. Lesser Palatine Ns - Lesser palatine foramina (behind GPN) - Soft palate and tonsil mucosa
5. Pharyngeal N - Palatovaginal canal - nasopharynx mucous membrane
6. Orbital branches - IOF - Orbital periosteum, orbitalis muscle
- Sphenoid/ethmoid sinuses
V3 - Mandibular nerve
Course & action
Exits ganglion with small motor root exits cranial cavity via Foramen Ovale to ITF between upper head LP and TVP
Branches from the main trunk
- Meningeal branch - Cartilagenous ET, posterior 1/2 of MCF dura, mastoid antrum/air cells (via FO or spinosum)
- N to Medial Pterygoid - Branches to TVP and tensor tympani- via Otic Ganglion (pass through without synapse)
Then divides as the ‘cat of nine tails’:
Anterior division - 6 branches
Posterior div - 3 branches
V3 - Mandibular nerve
Branches: distal in infratemporal fossa
(i.e. Ant & Posterior divisions)
Anterior division (motor except 1) 6 branches
- 2 x branches to Lat Pterygoid
- 2 x Temporal Nerves (anterior and posterior)
- N to Masseter (incl branch to TMJ, Hilton’s Law)
- Buccal N- between 2 heads of LP
Supplies thumb-sized cheek skin, then pierces buccinator to supply buccal mucous membrane, Secretomotor from Otic (buccal and molar glands) Vestibular gum of mandibular molars
Posterior division (sensory except 1) 3 branches
- Auriculotemporal N - 2 roots pass around middle meningeal a.
Secretomotor fibres Otic ganglion to Parotid (from IX via LSPN), curls around neck of mandible (branch to TMJ)
Auricular branch - EAM and pinna above EAM
Temporal branch - hairy skin of scalp
- Inferior Alveolar N - deep to lower head of LP, lies on MP between mandible and sphenomandibular lig
Enters mandibular foramen (gives of motor N to Mylohyoid - mylohyoid and ant belly digastric), supplies the posterior 5 teeth
Incisive branch - canine and both incisors
Mental N - exits mental foramen to supply lower lip and adjacent gum, incl fibres to labial glands
- Lingual N - joined by chorda, 2cm below BOS, deep to LP
Curves down on MP, above IAN, passing under superior constrictor, runs fwd on manidbular periosteum at posterior border of 3rd molar then on upper surface of Mylohyoid
Gingival branch - supplies lingual gum to midline
Runs below SM duct (gives off CT secretomotor fibres to SM ganglion), ascends on hyoglossus to supply ant 2/3 of tongue - common sensation and taste (CT fibres for taste, joins nerve 2cm below skull base)
CN VI
Nucleus
Nucleus - lower pons, near midline of 4th ventricle
CN VI
Course
Emerges , above pyramid of medulla (pontomedullary junction)
Turns upwards between AICA and pons
Pierces dura/arachnoid on clivus
Enters the inf petrosal sinus at the petrous apex
bends forward under petroclinoid lig (Dorello’s canal)
Passes fwd in cavernous sinus
- Longest intracranial course
Enters tendinous ring in SOF below inf division of III
Enters ocular surface of LR 1/3 along from lower border
Eye movements
Muscles & CNs
CN VII
Nuclei, nerve types & actions
Branchial Motor (VII):
- Cell bodies in Facial Nucleus in lower pons (below 4th ventricle). No tonotopic arrangement until more distal TB course
- Nerve of the 2nd arch (facial exp, Stapedius, PBD, Stylohyoid, posterior auricular — occipitalbelly of occipitofrontalis)
Nervus Intermedius (Nerve of Wrisberg):
1. Somatic sensory
- Cell bodies in geniculate ganglion, fibres travel with CN V (via Trigeminal sensory nucleus)
- Posterior EAC + conchal bowl (as per Hitselberger’s sign)
2. Visceral afferent
- Cell bodies in Nucleus of Tractus Solitarius
- Taste fibers: ant 2/3 of tongue (C/T), tonsil and soft palate (GSPN)
3. Visceral efferent
- Cell bodies in superior salivary nucleus (dorsal to VII nucleus)
- Secretomotor to lacrimal gland and glands of nose/palate/sinuses (via GSPN) via Pterygopalatine ganglion
- Secretomotor to submandibular/sublingual salivary glands (via C/T) via submandibular ganglion
CN VII
Sites/rate of dehisence
VII dehiscences:
- 55% of all temporal bones
- 91% in tympanic segment (<1% involve entire tympanic segment)
- MC above OW (83%)
- 13% at geniculate ganglion (cochleariform process)
- 9% in mastoid segment
- 26% have VII protrusion
CN VII
Course of nerve
(inc angles, lengths)
1. Intracranial
- Pontomedullary junction to porus of IAM 10-24mm
- No Perineurium in this segment. Difficult to distinguish from VS (may be splayed across tumour surface)
2. Intracanalicular (Meatal)
- Porus to fundus of IAM 5-12mm
3. Labyrinthine
- Fundus of IAM to Geniculate Ganglion 3-5mm
- 132 degrees to meatal segment
- Narrowest segment- canal = 0.68mm, nerve = 0.61mm (83% cf 73% in other areas). Thickening of periosteum causes this constriction
- Between cochlea and ampullated ends of SCCs
- Branches: GSPN at geniculate (to Facial Hiatus)
4. Tympanic Above and medial to cochleariform process
- Geniculate ganglion to 2nd genu 10-12mm
- 75 degrees to labyrinthine (pos/lat/inf), 10 degrees below plane of Lat SCC, 15 degrees laterally
Branches: Tympanic plexus branch (somatic sensory fibres)
5. Mastoid
- 2nd genu to SM foramen 10-14mm
- 95-125 degrees to Tympanic, tends laterally as it descends
- In its upper 2/3 it is related to the EAC — will be 3mm from the tympanic ring
- Below the level of the EAC it deviates from the canal
- Lateral deviation of the vertical portion is 2-3mm. May deviate medially instead
- Branches: N to Stapedius, CT (5mm above SM foramen), Auricular branch from vagus (Arnold’s Nerve)
6. Extratemporal
- Branches: Posterior auricular, N to PBD, N to Stylohyoid
- Division in parotid (pes anserinus): Temporozygomatic and cervicofacial
Total intratympanic portion is 28-30mm
CN VII
Lengths of portions
- Intracranial
- Pontomedullary junction to porus of IAM 10-24mm - Intracanalicular (Meatal)
- Porus to fundus of IAM 5-12mm - Labyrinthine
- Fundus of IAM to Geniculate Ganglion 3-5mm - Tympanic Above and medial to cochleariform process
- Geniculate ganglion to 2nd genu 10-12mm - Mastoid
- 2nd genu to SM foramen 10-14mm
CN VII
Relationships & Angles
Labyrinthine portion
- 132 degrees to meatal/intracanalicular segment
- Narrowest segment- canal = 0.68mm, nerve = 0.61mm (83% cf 73% in other areas). Thickening of periosteum causes this constriction
- Between cochlea and ampullated ends of SCCs
Tympanic
Above and medial to cochleariform process
- 75 degrees to labyrinthine (pos/lat/inf), 10 degrees below plane of Lat SCC, 15 degrees laterally
Mastoid
- 95-125 degrees to Tympanic, tends laterally as it descends
- In its upper 2/3 it is related to the EAC — will be 3mm from the tympanic ring
- Below the level of the EAC it deviates from the canal
- Lateral deviation of the vertical portion is 2-3mm. May deviate medially instead
CN VII
Branches
Labrythine Branch:
GSPN at geniculate (to Facial Hiatus)
Tympanic Branch:
Tympanic plexus branch (somatic sensory fibres)
Mastoid branches:
N to Stapedius
CT (5mm above SM foramen)
Auricular branch from vagus (Arnold’s Nerve)
Extratemporal branches:
Posterior auricular
N to PBD
N to Stylohyoid
Division in parotid (pes anserinus): Temporozygomatic and cervicofacial
CN VIII
Cochlear nerve: nuclei and neurons
Cochlear Nerve has 3 groups of neurons:
1st order - cell body in spiral ganglia (base of spiral lamina): bipolar
- Peripheral projection to IHC (Type I), OHC (Type II)
- Central processes run along modiolus and join into many small nerves (pierce dura/arachnoid at base of modiolus)
- Join to form cochlear nerve in IAC (antero-inf)
- Enter pontine cistern with vestibular nerve, then inf cerebellar peduncle at lower pons
2nd order - cell bodies in Cochlear Nuclei (dorsal and ventral) in inf cerebellar peduncle, floor of lateral recess of 4th ventricle
- Cross the medial lemniscus and ascend in the lateral lemniscus
3rd order - cell bodies in Medial Geniculate body - midbrain
- Central processes sent to internal capsule
May be more pathways depending on the intermediate relays
- trapezoid body (midbrain), lateral meniscus
? better to remeber as ECOLI
CN VIII
Vestibular nerve: divisions and neurons
Neuroepithelium - hair cells in maculae (utricle/saccule) and ampullae (SCCs)
Sup Vestibular N - sup/lat SCCs and utricle
Inf Vestibular N - post SCC (Singular N) and saccule
- Nerves pierces the superior and inferior cribrosa macula
1st order - Vestibular Ganglia in IAM. Central processes combine into the Vestibular N (joins Cochlear N)
2nd order - Vestibular Nuclei - lat/med/sup/inf, in lateral angle of 4th ventricle
- From here connections to cerebllum, spine (vestibulospinal tract) and cortical (bilateral thalamic relay in med geniculate body) to the auditory cortex
CN IX
Glossopharyngeal - Nuclei
Nerve of the 3rd branchial arch
Nuclei:
Inferior salivary nucleus (parasympathetic)
Nucleus ambiguus (motor)
Nucleus of the tractus solitarius (taste/sensory)
Main sensory nuclei of the trigeminal nerve (sensory)
CN IX
Glossopharyngeal - course
Emerges from medulla —> runs laterally behind the jugular tubercle of the occipital bone —> deeply notches the inferior border of the PTB (below IAM) —> inferior ganglion here —> sends branch to auricular branch of vagus —> anterior compartment of jugular foramen, lateral to inf petrosal sinus —> exits skull —> passes forward b/w IJV and ICA, beneath styloid apparatus —> curves medially between forks of ICA/ECA—> curves forward at lower border of stylopharygeus —> passes between superior and middle constrictor, deep to hyoglossus
CN IX
Glossopharyngeal - supplies what?
Supplies:
Palatine tonsil, mucous membrane of facues and base of tongue, mucous glands of the mouth
CN IX
Glossopharyngeal - Branches
Branches of CN IX:
- Tympanic (Jacobsen’s nerve) - passes into ME via inferior tympanic canaliculus (forms tympanic plexus) LSPN emerges from this via foramen ovale or petrosal foramen to the otic ganglion (parasympathetic)
- N to Stylopharyngeus - the only motor branch
- Carotid sinus nerve (aka Hering’s nerve)
- Pharyngeal branches - afferent fibres, form the pharyngeal plexus with CN X
- Tonsillar branch- afferent to tonsil mucosa
- Lingual branch- afferent to posterior 1/3 of tongue
Remember TongueS Poke Through Little Cunts
CN X
Vagus - Nuclei
Nuclei in upper part of medulla
Motor
- Branchial - Nucleus ambiguus (pharynx, larynx, palate, upper oesophagus)
- Visceral - Dorsal motor nucleus of Vagus (cardiac, bronchial, gut smooth muscle)
Sensory
- Somatic - Sensory nuclei of CN V
- Visceral - Nucleus of tractus solitarius
CN X
Vagus - Course
Leaves surface of medulla, below CN IX
Enters middle compartment of jugular foramen
1st order
- Small sup ganglion at jugular foramen (meningeal/auricular branches)
- Larger inf ganglion (nodose) just below jug foramen (all other sensory fibres)
- At the inf ganglion, CN XI gives all its nucleus ambiguus fibres to CN X
- SLN and pharyngeal plexus leave CN X at the inferior ganglion
Path:
Medulla —> middle compartment jugular foramen —> carotid sheath deep in the gutter b/w carotid and the IJV
CN X
Vagus - Branches
Cervical branches: Most Adults Can Play Some Roulette
- Small branches
- Meningeal
- Auricular (Arnold’s nerve)
- Carotid body - Pharyngeal- motor and sensory fibres to pharyngeal plexus. Runs between ICA and ECA
- Sup Laryngeal N- deep to ICA. Divides to Int Laryngeal N (pierces thyrohyoid memb) and Ext Laryngeal N (supplies cricothyroid)
- Cervical cardiac branches
- Right RLN- hooks under subclavian artery, runs in TO groove, under inf constrictor, behind cricothyroid joint to enter larynx
- Non-recurrent nerve assoc with anomalous retro-oesophageal location of right subclavian artery
Thoracic branches:
- Left RLN - hooks around ligamentum arteriosum
- Cardiac branches - from Vagi and RLNs
- Tracheal and Oesophageal branches - from main nerve (forming the oesophageal plexus)
- Vagal trunks - Ant and Post arise from oesophageal plexus, destined for the abdomen
CN X
Vagus - non recurrent laryngeal nerve courses
Non recurrent RLN
- Due to anomalies of branchial arteries
- Come off ~ level with cricoid, behind CCA to CTJ
- Right - 1% associated with retro-oesophageal subclavian artery (arises from left aortic arch)
- Left - very rare - assoc with situs inversus & anomalous left SCA
CN XI
Nuclei
Cranial fibres:
- Fibres arise in nucleus ambiguus
- Analogous to motor root of CN V
Spinal fibres:
- arise from C1-5 (mainly C2-4)- the spinal accessory nucleus
CN XI
Course
Formed in PCF by union of cranial and spinal roots
Occupies middle compartment of jugular foramen with X
The components are functionally distinct - merely ‘hold hands’ through the jugular foramen
Cranial fibres
- leave nerve in a branch that joins CN X in the jugular foramen (skeletal muscles of pharynx and palate)
Spinal Fibres
- arise from C1-5 (mainly C2-4)
- Emerge as a series of rootlets from lateral surface of cord, behind denticular lig
- Enter skull through foramen magnum
Course in the neck: Wholly motor, wholly spinal
Slopes down on IJV, deep to styloid process and PBD
Transverse proces C1
Gives off SCM branch then enters substance of SCM
Emerges at posterior border of SCM, 1cm above Erb’s point
Crosses posterior triangle and enters Trapezius 5cm above midpoint of clavicle
CN IX
Relationship to IJV
Relationship with IJV:
- Anterior 90%
- Posterior 5%
- Pierces IJV 5%
CN XII
Nucleus
A somatic motor nerve
Nucleus - medulla (midline, floor of 4th ventricle)
CN XII
Course
medulla (midline, floor of 4th ventricle)
Exit skull via hypoglossal canal (occipital bone)
Exit is deep (med/post) to jugular foramen
Course in the neck:
Spirals around inf ganglion of CN X, ICA, ECA (deep to IJV)
- Arteries deep veins superficial
Deep to styloid process, PBD
As it crosses ECA, held down by SCM branches and vena comitantes (may bleed indicating proximity to XII during ND)
Runs just above greater horn of hyoid
Passes forward on hyoglossus (deep to mylohyoid)
Supplies all intrinsic and extrinsic muscles of tongue except palatoglossus
CN XII
Branches
The only branches prior to the tongue, are from hitch-hiking C1 fibres
- Meningeal branch ( re-enters via hypoglossal canal, supplies PCF posterior to foramen magnum)
- Descendens Hypoglossi (upper root of ansa cervicalis)
- N to thyrohyoid
- N to geniohyoid
