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Bloc J - Neuro > Oct3 M1-Cranial Nerves > Flashcards

Oct3 M1-Cranial Nerves Flashcards

1
Q

6 first cranial nerves

A

-I: olfactory
-II: optic
-III: oculomotor
-IV: trochlear
-V: trigeminal
-VI: abducens
Ouh, ouh, ouh, to touch and feel very good velvet, such heaven.

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2
Q

cranial nerve nucleus def

A
  • group of neuronal cell bodies that is within the brainstem

- cranial nerve axons (nerve) = PNS

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3
Q

nerves position approx. (I to VI) in view form the bottom

A
  • I: big on top going frontally
  • II: also big, out of midbrain going under I
  • III: below II, from midbrain and pons junction
  • IV: goes posteriorly (to the top), form pons. so can’t see in this view
  • V: from sides of pons
  • VI: most medial of the 3 CNs (6,7,8) coming off pons-medulla junction
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4
Q

olfactory n. dysfunction on hx

A

smell or taste dysfunction (taste is actually smell)

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5
Q

olfactory n. nucleus is where

A
  • not one discrete nucleus

- complex central connections to olfactory cortex, amygdala and autonomic centres

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6
Q

olfactory n. path taken (and where the problem in it could be) (note: the afferent smell signal follows the opposite path)

A
  • out of midbrain anteriorly
  • exits the skull via the multiple holes of the cribiform plate of the ethmoid bone (sends axons through these holes)
  • goes to the olfactory bulb (most ant part of olfactory system)
  • inn. the olfactory epithelium in the nose
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7
Q

how to examine for olfactory n. fct

A
  • put non-noxious substance under one nostril with patient’s eyes closed and other nostril occluded
  • ask to ID the substance (use ground coffee or spices)
  • not done routinely, only if suspicion*
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8
Q

what is unique about the olfactory n.

A
  • cribiform plate with INDIVIDUAL axons passing through the holes
  • makes them very susceptible to traumatic injury
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9
Q

optic nerve (II) dysfunction: what patients complain of

A

one of these two things

  • decreased acuity (see everything but not very well)
  • visual field defect (part of field they don’t see)
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10
Q

four things to check on physical exam to check optic n. fct

A
  • fundi = place where vasculature of retina is (using an ophthalmoscope)
  • visual acuity (using Snellen chart (of opto), can have on phone)
  • visual fields
  • pupil reflex (reaction to light).
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11
Q

two kinds of visual fields defect with optic n. problem

A
  1. scotoma (pathology of optic nerve): area within visual field where patient does not see anything
  2. loss of quadrant or hemifield of the visual field (pathology of optic chiasm or more post structures)
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12
Q

what n. are responsible for the pupils reflex to light

A

CN II and III but we test it with CN II

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13
Q

path the afferent signal follows in the optic nerve

A
  • retina (cone and rod photoreceptors)
  • bipolar cell (primary)
  • ganglion cell (secondary), sends axons which follow the following path
  • optic nerve (exits orbit and enters skull via optic canal)
  • optic chiasm (there, axons from nasal half of retina cross contralateral and axons form temporal half of retina stay ipsilateral)
  • optic tract
  • thalamus (back of brain)
  • a 2nd neuron travels all the way back to the occipital lobe
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14
Q

thing to note about olfactory and optic nerve

A

both are really just tracts (+ in optic n, the names optic nerve, chiasm and tract are just diff names given to the same ganglion cell axons)

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15
Q

what is unique about the optic n.

A
  • retina and optic n. are a tract and not a nerve bc are part of CNS bc arise from diencephalon
  • increased ICP directly affects optic n. and retina.: can see this as papilledema with the ophthalmoscope (swelling, bump in back of the eye, on retina)
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16
Q

oculomotor n. function

A
  • inn. 4 of the 6 extraocular muscles
  • inn. 1 of the 2 eyelid elevator muscles
  • constricts the pupil (involved in pupil reflex like CN II)
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17
Q

oculomotor n. dysfunction signs

A

in order to check**:

  • ptosis (drooping of upper eyelid)
  • diplopia (alignement of the eyes, normally perfectly aligned)
  • mydriasis (enlargement of the pupil) (would look for pupil asymmetry: one bigger than other)
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18
Q

location of the oculomotor n. nuclei

A

in midbrain,

  • principal (main motor) nucleus (more medial)
  • Edinger-Westphal nucleus (more lateral)
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19
Q

what Edinger-Westphal nucleus of CN III does

A

has the PSS fibers causing the pupils to constrict

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20
Q

cavernous sinus anatomy

A
  • bilateral space contained between bone in middle of base of skull and temporal lobe covered with dura mater
  • the dura mater split in two spaces to give this cavernous sinus
  • contains venous blood so is a venous sinus
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21
Q

structures relating to the venous sinus

A

top to bottom bilaterally

  • internal carotid artery coming back after looping (on top)
  • CN III
  • CN IV
  • CN V branch 1 (VI)
  • CN V branch 2 (V2)
  • CN VI (going medially now)
  • internal carotid artery starting its loop (going even more medially)
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22
Q

path of the oculomotor n.

A
  • midbrain
  • cavernous sinus (first CN on top) = a venous sinus with venous blood contained in layers of dura
  • exits through the skull through the SUPERIOR ORBITAL FISSURE
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23
Q

pathologies of the cavernous sinus that can affect the CNs there (III, IV, V, VI)

A
  • infection

- fistulas between arterial and venous blood causing higher pressure

24
Q

what is unique about the oculomotor n.

A

both motor and PSS fcts with DUAL nuclei

25
Q

trochlear nerve (CN IV) fct

A

inn. the superior oblique muscle of the eye (1 of the 6 extraocular muscles)

26
Q

course that the superior oblique muscle takes

A
  • medial wall of orbit in the back
  • comes off medial wall and goes to the front but still close to medial wall of orbit
  • as it does this, passes under the trochlea, piece of bone acting like a hook (is why n. to this m. is trochlear n.)
  • after trochlea, hooks back laterally posteriorly to attach to top of eye latero posteriorly
27
Q

function of trochlear m.

A

inward rotation (called intorsion) of the eye and depression of the eye

28
Q

how to test for trochlear n. dysfunction, what will patient complain about

A

diplopia when looking down and in (medially): as when go down the stairs or read a book

29
Q

how to examine for trochlear n. (IV)

A

test for ocular movements

30
Q

trochlear n. nucleus location

A

in the midbrain, more caudally and dorsally

31
Q

what is unique about the trochlear n.

A
  • exits the brainstem (midbrain specifically) dorsally
  • crosses over to the other side
  • ALL OTHER CNs stay ipsilateral
32
Q

path the trochlear n. takes

A
  • exits midbrain caudally to CN III and dorsally
  • goes through cavernous sinus
  • exits skull via superior orbital fissure (like CN III)
33
Q

how to verify trigeminal n. function clinically

A

ask about face sensation. to be thorough, have to examine sensation in each division. FROM FRONT OF EAR ONWARD,

  • V1 goes to eye and nose
  • V2 to cheek and upper lip
  • V3 to lower lip, jaw, chin
34
Q

for V1, other thing you can test than face sensation

A

corneal reflex

  • cornea = clear part of the eye sitting over the sclera (the white of the eye that is insensitive to touch).
  • cornea is sensitive to touch
35
Q

what’s the corneal reflex (touch cornea with kleenex)

A
  • afferent arm of reflex = V1 branch connects to both CN VII in brainstem
  • efferent arm: CN VII causes BOTH eyes to blink
36
Q

what is the direct and the consensual response in the corneal reflex

A
  • direct = blinking of eye you touched

- consensual = blinking of contralateral eye

37
Q

what happens if problem with CN VII on one side

A

in the corneal reflex, only one (same) eye blinks, no matter on which side you do the corneal reflex

38
Q

what happens if problem with CN V (in corneal reflex)

A

no eye blinking at all (if damaged on the side where you test the reflex)

39
Q

nuclei of CN V are where

A
  • has many

- most are in the PONS

40
Q

path taken by CN V

A
  • exits brainstem at the mid-pons
  • ganglion where the cell bodies are located (CN V, like I and II, has sensory function. note CN V also has a motor fct)
  • cavernous sinus (V1 and V2), the trigeminal n. passes near anteriorly and close to several arteries
  • V1 (ophthalmic n.) goes through superior orbital fissure
  • V2 (maxillary nerve) goes through foramen rotundum)
  • V3 (mandibular nerve) goes through foramen ovale (right after ganglion. doesn’t go through cavernous sinus)
41
Q

diff nuclei of trigeminal nerve (CN V)

A

all in the pons

  • motor nucleus (V3) for muscles of mastication and others
  • mesencephalic nucleus (for proprioception = position) (this one comes from midbrain, hence the mesencephalic name)
  • sensory nucleus (THE MAIN NUCLEUS) (for touch, pain, temperature)
42
Q

mesencephalic nucleus: imp thing about cell bodies

A
  • are located in the nucleus
  • are not in the ganglion (whereas cell bodies of sensory nucleus + all other neurons for sensation in the face are in ganglion)
  • the nucleus extends rostrally in the midbrain (mesencephalon)
43
Q

2 parts of the sensory nucleus of CN V

A
  • principal (pontine) (touch)

- nucleus of the spinal tract (pain and temp)

44
Q

special thing about sensory neurons of CN V sensory nucleus

A

pseudounipolar

  • one cell body in ganglion
  • two axons (one to sense, other to synapse on spinal tract nucleus)
45
Q

trigeminal n (CN V) testing key thing

A

is there sensation in the face for the 3 divisions

  • don’t worry about testing what sensory info (touch, pain, etc.)
  • CN V lesions DOESN’T cause motor prob (other than mastication weakness)
46
Q

unique things about trigeminal n.

A
  • facial numbness (loss of sensation) and pain

- corneal reflex to test V1 ONLY**

47
Q

what is trigeminal neuralgia

A
  • brief, severe, lancinating or electric pain to the face
  • provoked by touch, chewing, wind or cold
  • only div1 affected
48
Q

causes of trigeminal neuralgia

A

either

  • vascular compression of the CN V when passes near artery (bc of pulsation)
  • idiopathic
49
Q

function of the abducens n.

A

-inn. lateral rectus muscle (which ABDucts the eye = turns it out)

50
Q

what patient complains of in abducens n. dysfct

A

horizontal diplopia

51
Q

how we examine, test for abducens n. dysfct

A

examine the extra-ocular mvmts

52
Q

abducens n. trajectory

A
  • exits pons caudally most medially (more medial than VII)
  • passes through cavernous sinus (more medially than III, IV, V)
  • exits skull via superior orbital fissure, to go to the orbit
53
Q

imp thing about VI and VII (facial n.) relation

A
  • VII loops around VI
  • this forms a bump in the floor of the 4th ventricle
  • bump called the facial colliculus
  • therefore VII exits more lat
54
Q

unique feature of VI

A

false localizing sign

55
Q

def of false localizing sign

A
  • abducens n. = smallest in the body in terms of axons so is fragile
  • disease (like tumor) elsewhere in the brain causes increased ICP
  • VI is indirectly affected (whereas other CNs = think of direct pathologies = on course that the CN takes)
  • so CN VI = horizontal diplopia, anomaly in extra-ocular mvmts, lesion can be in pons nucleus, cavernous sinus OR anywhere in brain

Bloc J - Neuro (60 decks)

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