12: Vertigo

Question 1

Vertigo

Answer 1

feeling that you are moving when when you are stationary

Question 2

Types of motion

Answer 2

Types of motion:
• Rotations: Semi-circular canals (rotational acceleration)
• Translations: Otoliths

Canals are most sensitive to rotations orthognal to their plane:
• we have 6 different rotated ones

Question 3

Hair cells

Answer 3

directionally selective:
• can detect motion in one direction much better than in other
• Afferents can be excited by to 400 spikes/second, but can only be inhibited to 0 spikes/second

Question 4

Plains of movement

Answer 4

• RH LH (right / left horizontal)
• RALP (right anterior / left posterior)
• LARP left anterior / right posterior)
-> Excited by rotations towards the ear- side, inhibition on the other side

After rotation, viscosity of endolymph & elasticity of cupula cause
cupula to return to its static position slowly, over several seconds (lange Refraktärzeit)
->Signals on vestibular afferents more closely match velocity than acceleration
-> but sensitive to acceleration!!

Question 5

Alcohol

Answer 5

1. Alcohol is lighter then endolymph fluid
2. It gets more quickly into the cupula than the canal
3. Buoyancy of the cupula deflects hair cells

Question 6

Vestibulo-ocular reflexes (VOR):

Answer 6

• image stabilization system
• reaction time of VOR = less than 10 msec -> fastest reflex bc only 3 neurons involved

When vestibular nerve on one side damaged: (right)
• Imbalance
• eye stops rotating in right direction
• Fast eyemovements (slow, then fast saccade back)
• Eye thinks its active inhibition -> feels like rotating to left
• Takes weeks until brain adapts

Question 7

Otholiths

Answer 7

Sensitive to translation & gravity:
• cannot discriminate btw head acceleration and head tilt
• utricle encodes linear acceleration in horizontal plane (fore-aft, left-right)
• saccule encodes acceleration in vertical plane (up-down, left-right)

Question 8

Vestibular evoked myogenic potentials (VEMP):

Answer 8

1. vestibular system is sensitive to sound
2. otoliths cause torsional eye movements

Question 9

Visual-Vestibular symbiosis:

Answer 9

• detect info about movement
• VOR is good for fast movements, but not for slow
• Visual processing is too slow for fast movements, but can direction eye movements for slow motion

Question 10

Balance

Answer 10

Vestibular pathways originating from vestibular nucleus in brainstem
1. Medial vestibulospinal tract: Control of neck muscles
2. Lateral vestibulospinal tract: Extends the length of spinal cord to innervate muscles of trun

Question 11

Bedside testing

Answer 11

• spontaneous nystagmus?
• head impulse test
• vertical ocular deviation?
• dynamic visual acuity
• Romberg on foam
• provocation maneuvers
• bimalleolar vibration sense

Question 12

Alexanders law (Nystagmus):

Answer 12

Drift velocity (and therefore nystagmus frequency) increases in direction of quick phases

Question 13

Headimpulse test

Answer 13

Positive when catchup saccade

“Negative” head impulse test:
• best predictor of stroke in acute vestibular syndrome (“misses” stroke in 1/10 patients)

Overt vs. Covert saccades

Question 14

Ocular tilt reaction:

Answer 14

• double vision
• Latentes Schielen
• most frequent in Wallenberg’s syndrome (stroke of brainstem/cerebellum)

Question 15

Dynamic visual acuity:

Answer 15

more than 2 lines difference when shaking head than when still

Question 16

Romberg on foam

Answer 16

• close eyes standing on foam
• start to sway and fall

Question 17

benign paroxysmal position vertigo (BPPV):

Answer 17

Posterior canalithiasis
• wenn Kristall in Kanal gelangen, mit best. Bewegungen wieder raus bringen
Provocation maneuvers
1. Hallpike on both sides
2. Supine roll on both sides, 3 times each
3. Hallpike on both sides
-> Wait long enough for positioning nystagmus!

Etiologies
• 50% idiopathic
• 17% traumatic
• 15% after vestibular neuritis