Cranial Nerve Neuroanatomy

Question 1

What is the pathway of the olfactory nerve?

Answer 1

Nasal mucosal neuroepithelium

Through cribriform plate

Into anterior cranial fossa

To the olfactory bulb

Bypasses the thalamus

Into the temporal lobe uncus

Olfactory cortex

Limbic system

Question 2

What is the pathway of the optic nerve?

Answer 2

Bipolar first neurons

Ganglion cell second neurons

Optic nerve in muscle cone

Into the optic canal

Enters middle cranial fossa

Decussate at the optic chiasma above pituitary

Optic tract passes round the cerebral peduncles of the midbrain

Relay in lateral geniculate body to the visual cortex in calcarine sulcus of occipital lobe

Via retrolentiform part of the internal capsule and optic radiation

Superior brachium to the pretectal nucleus for pupillary light reflexes

To the superior colliculus for generalized light reflexes

Question 3

What is the pathway of the oculomotor nerve?

Answer 3

Ocumolotor and EW nuclei in midbrain superior colliculus level

Through the red nucleus

Emerge from medial base of cerebral peduncles

Into the interpeduncular cistern

Between superior cerebellar artery and posterior cerebral artery

Below the posterior communicating artery

Free margin of tentorium cerebelli

Roof of cavernous sinus

Lateral wall of cavernous sinus, picks up sympathetic fibers

Medial and inferior to IV and V1

Divides into superior and inferior divisions

Question 4

What is the pathway of the oculomotor nerve?

Answer 4

Trochlear nuclei at inferior colliculus of midbrain

Cross the midline within the midbrain

Exit posteriorly below the inferior colliculus

Round the peduncles

Between posterior cerebral and superior crenellations arteries

Under the free margin of the tentorium cerebelli

Roof of cavernous sinus

Lateral wall of cavernous sinus

Above the III nerve

Enters superior orbital fissure outside tendinous ring

Question 5

What is the pathway of the trigeminal nerve?

Answer 5

Mesencephalic nucleus - proprioception
Main sensory nucleus - light touch
Nucleus of descending trigeminal tract - pain and temperature
Trigeminal motor nucleus - muscles of mastication

Exit at midpontine level, sensory root and motor root medial to it

Below tentorium cerebelli

Trigeminal cave on apex of Petrous bone

Trigeminal ganglion with motor root below

3 sensory divisions (ophth, max, mand)

V1 to cavernous sinus lateral wall, then orbit

V2 to cavernous sinus lateral wall, then foramen rotundum, into pterygopalatine fossa, ends as infraorbital nerve

V3 exits with motor root through foramen ovale, into infratemporal fossa, divides into anterior and posterior divisions

V1 and V2 are sensory

V3 motor

• anterior division only sensory branch = buccal
• posterior division lingual nerve gives somatic sensation to anterior 2/3 of tongue

Question 6

What is the pathway of the abducens nerve?

Answer 6

Abducens nucleus in lower pons

Beneath facial colliculus

Nerve emerges in lower pons, above medullary pyramid

Into the prepontine cistern

Goes up between pons and anterior inferior cerebellar artery

Beneath dura of clivus

Over apex of petrous temporal bone

Into the cavernous sinus

Forwards, inferolateral to ICA

Into the tendinous ring

Question 7

What is the pathway of the facial nerve?

Answer 7

Facial nucleus in lower pons

Fibers curve round the abducens nucleus to make the facial colliculus

Nerve exits between pons and medullary olive

Into the CPA

Into the internal acoustic meatus with VIII

Laterally in petrous bone above vestibule of inner ear

Bends posteriorly at geniculate ganglion a long the medial wall of middle ear

Bends inferiorly into the facial canal

Emerge from stylomastoid foramen

Into the parotid , upper trunk and lower trunk

5 terminal branches