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*RACS ENT Fellowship > Anatomy - Cranial nerves > Flashcards

Anatomy - Cranial nerves Flashcards

1
Q

LOCATION OF CRANIAL NERVE NUCLEI

III - VI

A

III - Midbrain (superior colliculus)

IV - Midbrain (inferior colliculus)

V -

  1. Motor- upper pons
  2. Mesencepalic- entire length of midbrain
  3. Main sensory- upper pons (lateral to motor)
  4. Spinal- lower pons, medulla to C3

VI - Lower pons

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2
Q

LOCATION OF CRANIAL NERVE NUCLEI

VII - XII

A

VII - Pontomedullary junction

VIII - Lateral medulla (encroaching on pons)

IX - Medulla (and lowest part of pons)

X - Upper part of medulla

  1. Branchial motor- nucleus ambiguus
  2. Visceral efferent- dorsal motor nucleus of the vagus
  3. Visceral afferent- nucleus of the tractus solitarius

XI -

  1. Cranial root- nucleus ambiguus (medulla)
  2. Spinal root- ‘spinal accessory nucleus’ ant horn of C1-6 (esp 2-4)

XII - Medulla

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3
Q

CRANIAL NERVES

NERVE FIBRE TYPES - Branchiomotor

A
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4
Q

CRANIAL NERVES

NERVE FIBRE TYPES - Somatic sensory

A
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5
Q

CRANIAL NERVES

NERVE FIBRE TYPES - Visceral Motor (PNS)

A
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6
Q

CRANIAL NERVES

NERVE FIBRE TYPES - Somatic Motor

(I.e. muscles Not from branchial arches)

A
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7
Q

CRANIAL NERVES

NERVE FIBRE TYPES - Sensory

(General and Special visceral)

A
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8
Q

CRANIAL NERVES

NERVE FIBRE TYPES - Special senses

A
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9
Q

CRANIAL NERVES

NUCLEI - Location in brain stem

A
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10
Q

Lingual Nerve

Course (& relations in infratemporal fossa)

A
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11
Q

Cranial Nerve parasympathetic pathways

Lacrimal gland

A

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

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12
Q

Cranial Nerve parasympathetic pathways

Nasal

A

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)

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13
Q

Cranial Nerve parasympathetic pathways

Partoid gland

A

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

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14
Q

Cranial Nerve parasympathetic pathways

SMG & sublingual glands

A

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

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15
Q

Cranial Nerve parasympathetic pathways

Sphincter pupillae and ciliaris muscles

A

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)

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16
Q

CN III

Nucleus

A

Nucleus in midbrain at level of superior colliculus (floor of aqueduct)

  1. Somatic - motor to striated ocular muscles
  2. Visceral - motor to smooth muscle of eye

Edinger-Westphal Nucleus (cranial to somatic nucleus)

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17
Q

CN III

Course

A

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

  1. MR
  2. IR
  3. 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)
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18
Q

CN III

Palsy

A

Down & Out

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19
Q

CN IV

Nucleus

A

Nucleus: Midbrain at level of inferior colliculus

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20
Q

CN IV

Course

A

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)

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21
Q

CN IV

Action & Testing

A

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)

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22
Q

CN V

Nucleus

A

Nuclei:

Motor - upper pons, 1st branchial arch

3 parts of the sensory nucleus, spans length of brainstem

  1. Mesencephalic - length of midbrain, proprioceptive
  2. Main sensory - upper pons lateral to motor nucleus, touch
  3. Spinal - lower pons to medulla and through to C3, pain and temp
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23
Q

CN V

Course

A

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

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24
Q

CN - V1

Course & Branches

A

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

25
Q

Lacrimal Nerve

Course & Action

A

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

26
Q

Frontal Nerve

Course and Action

A

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

27
Q

Nasociliary / Anterior Ethmoid Nerve

Course & action

A

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
28
Q

V2 - Maxillary Nerve

Course & Action

A

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

  1. Middle Meningeal N - ant 1/2 of MCF
  2. Ganglionic branch - V2 —> PPG —> Branches of ganglion (x6, see next facet)
  3. Posterior Superior Alveolar N
  4. 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
29
Q

V2 - infraorbital branch

Course & Action

A

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)
30
Q

Pterygopalatine ganglion Branches

A

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
31
Q

V3 - Mandibular nerve

Course & action

A

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

  1. Meningeal branch - Cartilagenous ET, posterior 1/2 of MCF dura, mastoid antrum/air cells (via FO or spinosum)
  2. 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

32
Q

V3 - Mandibular nerve

Branches: distal in infratemporal fossa

(i.e. Ant & Posterior divisions)

A

Anterior division (motor except 1) 6 branches

  1. 2 x branches to Lat Pterygoid
  2. 2 x Temporal Nerves (anterior and posterior)
  3. N to Masseter (incl branch to TMJ, Hilton’s Law)
  4. 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

  1. 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

  1. 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

  1. 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)

33
Q

CN VI

Nucleus

A

Nucleus - lower pons, near midline of 4th ventricle

34
Q

CN VI

Course

A

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

35
Q

Eye movements

Muscles & CNs

A
36
Q

CN VII

Nuclei, nerve types & actions

A

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
37
Q

CN VII

Sites/rate of dehisence

A

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
38
Q

CN VII

Course of nerve

(inc angles, lengths)

A

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

39
Q

CN VII

Lengths of portions

A
  1. Intracranial
    - Pontomedullary junction to porus of IAM 10-24mm
  2. Intracanalicular (Meatal)
    - Porus to fundus of IAM 5-12mm
  3. Labyrinthine
    - Fundus of IAM to Geniculate Ganglion 3-5mm
  4. Tympanic Above and medial to cochleariform process
    - Geniculate ganglion to 2nd genu 10-12mm
  5. Mastoid
    - 2nd genu to SM foramen 10-14mm
40
Q

CN VII

Relationships & Angles

A

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
41
Q

CN VII

Branches

A

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

42
Q

CN VIII

Cochlear nerve: nuclei and neurons

A

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

43
Q

CN VIII

Vestibular nerve: divisions and neurons

A

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
44
Q

CN IX

Glossopharyngeal - Nuclei

A

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)

45
Q

CN IX

Glossopharyngeal - course

A

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

46
Q

CN IX

Glossopharyngeal - supplies what?

A

Supplies:

Palatine tonsil, mucous membrane of facues and base of tongue, mucous glands of the mouth

47
Q

CN IX

Glossopharyngeal - Branches

A

Branches of CN IX:

  1. 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)
  2. N to Stylopharyngeus - the only motor branch
  3. Carotid sinus nerve (aka Hering’s nerve)
  4. Pharyngeal branches - afferent fibres, form the pharyngeal plexus with CN X
  5. Tonsillar branch- afferent to tonsil mucosa
  6. Lingual branch- afferent to posterior 1/3 of tongue

Remember TongueS Poke Through Little Cunts

48
Q

CN X

Vagus - Nuclei

A

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
49
Q

CN X

Vagus - Course

A

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

50
Q

CN X

Vagus - Branches

A

Cervical branches: Most Adults Can Play Some Roulette

  1. Small branches
    - Meningeal
    - Auricular (Arnold’s nerve)
    - Carotid body
  2. Pharyngeal- motor and sensory fibres to pharyngeal plexus. Runs between ICA and ECA
  3. Sup Laryngeal N- deep to ICA. Divides to Int Laryngeal N (pierces thyrohyoid memb) and Ext Laryngeal N (supplies cricothyroid)
  4. Cervical cardiac branches
  5. 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:

  1. Left RLN - hooks around ligamentum arteriosum
  2. Cardiac branches - from Vagi and RLNs
  3. Tracheal and Oesophageal branches - from main nerve (forming the oesophageal plexus)
  4. Vagal trunks - Ant and Post arise from oesophageal plexus, destined for the abdomen
51
Q

CN X

Vagus - non recurrent laryngeal nerve courses

A

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
52
Q

CN XI

Nuclei

A

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
53
Q

CN XI

Course

A

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

54
Q

CN IX

Relationship to IJV

A

Relationship with IJV:

  • Anterior 90%
  • Posterior 5%
  • Pierces IJV 5%
55
Q

CN XII

Nucleus

A

A somatic motor nerve

Nucleus - medulla (midline, floor of 4th ventricle)

56
Q

CN XII

Course

A

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

57
Q

CN XII

Branches

A

The only branches prior to the tongue, are from hitch-hiking C1 fibres

  1. Meningeal branch ( re-enters via hypoglossal canal, supplies PCF posterior to foramen magnum)
  2. Descendens Hypoglossi (upper root of ansa cervicalis)
  3. N to thyrohyoid
  4. N to geniohyoid
58
Q
A

*RACS ENT Fellowship (19 decks)

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