Cranial Nerves

Question 1

CN1 (Name, foramen, nuclei, components, function)

What is it close to?

Answer 1

Olfactory n. Pierces cribriform plate on eithmoid bone. No CN nuclei. SVA (smell). In close proximity to hippocampus.

Question 2

CN II (Name, foramen, nuclei, components, function)

Answer 2

Optic n. Passes through optic foramen. Lateral geniculate body. SSA (vision)

Question 3

CN III (Name, foramen, nuclei, components, function)

Answer 3

Occulomotor n. Superior orbital fissure. Edinger-Westphal = GVE nucleus. Occulomotor nucleus = GSE nucleus. GVE=parasympathetics, ciliary ganglion makes lens fat and pupil constrict (accomodation). GSE=eye muscles LR6(SO4)3.

Question 4

CN IV (Name, foramen, nuclei, components, function)

What two things are unique to this CN?

Answer 4

Trochlear nerve. Superior orbital fissure. Trochlear nucleus. GSE (superior oblique muscle). Only nerve to come from dorsal side of brainstem and decussates. Susceptible to injury because of long course.

Question 5

Where in the brainstem are the Cranial Nerve nuclei located?

Answer 5

CNI and II not really attached to brainstem.
CN III and IV in midbrain.
CN V, VI, VII, VIII in pons.
CN IX, X, XI, XII in medulla.

Question 6

CN V (Name, foramen, nuclei, components, function)

Where does it synapse in the thalamus

Answer 6

Trigeminal, GSA and SVE
V1: Opthalmic, sup. orb. fissure, upper face GSA
V2: Maxillary, foramen rotundum, middle face GSA
V3: Mandibular, foramen ovale, lower face and ant 2/3 tongue GSA

Nuclei:

1. Motor neuron of V: motor fibers (SVE) of V
2. Spinal nucleus: pain and temp
3. Main sensory nucleus: conscious proprioception (touch and jaw position)
4. Mesenphalic nucleus: unconscious proprioception from jaw V3 (jaw reflex!)

Trigeminal thalamic fibers synapse in VPM of thalamus.

Question 7

CN V analogs

1) Trigeminal ganglion
2) Mesencephalic nucleus
3) Main sensory nucleus
4) Spinal nucleus
5) Trigeminal motor nucleus

Answer 7

1) semilunar or Gassarian (pseudounipolar cells conveying sensory info from the head)
2) more pseudounipolar cells (like DRG) sucked into the brainstem
3) nucleus gracilis and cuneatus (DCP), relays position and touch
4) nucleus proprius and STT, pain and temp
5) SVE to muscles of mastication (first arch muscles)

Question 8

CN VI (Name, foramen, nuclei, components, function)

Jabbing pin

Answer 8

Abducens n. Superior orbital fissure. Abducens nucleus. GSE (lateral rectus muscle). Jabbing pin into facial colliculus will jack up the abducens nerve.

Question 9

CN VII (Name, foramen, nuclei, components, function)

Answer 9

Facial n. Internal auditory meatus
GVA: Nuc. solitarius (upper), soft palate
SVA: Nuc. solitarius (lower), taste ant 2/3 tongue
GVE: sup. salivatory nuc., parasympathetics (lacrimal, nasal, submandibular, sublingual glands)
GSA: sensory nucleus of CN5, ear pinna
SVE: motor nucleus of 7, motor to muscles of facial expression

Question 10

Upper motor neuron injury to CN VII motor nucleus

Lower motor neuron injury to CN VII motor nucleus

Answer 10

Neurons innervating upper face receive bilateral cortical input. Neurons innervating lower face receive contralateral cortical input ONLY.

Upper injury: (e.g. cortical stroke) loss of lower face on contralateral side, upper face spared.

Lower injury: (e.g. Bell’s palsy) loss of both upper and lower face on ipsilateral side.

Question 11

CN VIII (Name, foramen, nuclei, components, function)

Answer 11

Abducens n. Internal auditory meatus. Cochlear nuclei and vestibular nuclei. SSA (sound).

Question 12

SLO

AIM

Answer 12

Superior colliculus, lateral geniculate, optic stuff

Auditory stuff, inferior colliculus, medical geniculate

Question 13

CN IX (Name, foramen, nuclei, components, function)

Answer 13

Glossopharyngeal n. Jugular foramen.
GVA: nuc. solitarius, deep sensory to pharynx
SVA: nuc. solitarius, taste to post. 1/3 tongue
GVE: inferior salivatory nuc., GLOAP (parotid gland)
GSA: sensory nucleus of 5, ear pinna
SVE: ambiguus nuc., stylopharyngeaus m.

Question 14

CN X (Name, foramen, nuclei, components, function)

Answer 14

Vagus n. Jugular foramen
GVA: nuc. solitarius, deep sens below pharynx
SVA: nuc. solitarius, taste buds in epiglottis and glottis
GVE: dorsal motor nuc of 10, thoracic and abdominal viscera
GSA: sensory nucleus of 5, ear pinna
SVE: nuc ambiguus, muscles of pharynx and larynx

Question 15

CN XI (Name, foramen, nuclei, components, function)

Answer 15

Spinal accessory n. Jugular foramen. Accessory nucleus (C1-C5). SVE (trapezius and sternocleidomastoid)

Question 16

CN XII (Name, foramen, nuclei, components, function)

Answer 16

Hypoglossal n. Hypoglossal canal. Hypoglossal nucleus. GSE (intrinsic and extrinsic muscles of the tongue)