Neuro 26: Vestibular Disorders

Front 1

what is the difference between vertigo and dysequilibrium

Back 1

vertigo=room spinning, nystagmus dysequilibrium= internal spinning

Front 2

what affect will activation of a unilateral horizontal canal have on the eyes

Back 2

eyes will deviate contralaterally. Activation of the canal occ when the head turns that way (so if you turn your head to the left, you activate the left canal and your eyes deviate right)

Front 3

Expalin what is happening in the horizontal canal when you turn your head to the left

Back 3

WHen you turn your head to the left, the fluid in your ducts moves to the right. In the left duct, this right-ward motion of the fluid defelects the cupula to the right, towards the utricle which depolarizes the hair cells. In the right duct, the right-ward motion of the fluid deflects the cupula away from the utricle thus hyperpolarizing the cells (see notle pg 372 fig 14-32)

Front 4

what affect does activation of the anterior SCC have on the eyes

Back 4

the eyes deviate up

Front 5

what affect does activation of the posterior canal have

Back 5

eyes deviate down

Front 6

which direction does the slow phase of nystagmus go towards

Back 6

slow phase goes toward the hypoactive side, with the VOR, the slow phase is opposite the direction you are turning your head (if you are turning your head left, the left canal is hyperactive, the right canal is hypoactive, the eyes deviate right)

Front 7

the fast phase of nystagmus is mediate by...

Back 7

the cortex (comatose pt may have slow but not fast)

Front 8

Ischemic stroke to the labyrinthine artery can cause a vestibular disorder. Describe what you would expect to find

Back 8

This is an acute, deactivating lesion. The canal on the affected side would be hypoactive so you would expect slow phase towrads thside

Front 9

What is the cause and presentation of BPPV

Back 9

cause=otoconia detach from the wall of the utricle, fall into semicircular canal (usually posterior) and create an activating lesion. Pt presents with vertigo, triggers when turning over, pefers to sleep with that ear up

Front 10

In right sided BPPV, otoconia moving through the right vestibular system create an activating lesion. Which side would you expect the slow phase to occur towards? Fast phase? What muscles are invovled?

Back 10

The activating lesion in the right SCC mimics a head turn to the right. The the slow phase will be to the left and the fast phase will be to the right as the brain cortex detects the deviation and triggers a reflex jerk. In order to hold the eyes to the left in the slow phase the ipsilateral SO and contralateral IO will be engaged.

Front 11

WHich manuever is used to Dx BPPV

Back 11

Dix-Hallpike. Turn the head toward the side suspected of having the lesion and then thrust the head downwards. The slow phase will be up towards the celing away from the lesion and the fast phase will be towrads the floor (geocentric nystagmus)

Front 12

What maneuver is used to treat BPPV

Back 12

Epley. Slow rotate pt's head to flush out otoconia, begin by turning head towards affected side then sequentially rotate away stay upright for 24-48 hrs, do not sleep on affected side for 5 nights

Front 13

Describe a peri-lympahtic fistula

Back 13

allows leakage of endolymph which creates an activating lesion in the affected side

Front 14

Describe Meniere's disease

Back 14

abnormal accumulation of endolymphatic fluid tha tmies with perilymph from cochlear systme, activating lesion, can have tumarkin's otolihthic crisis due to interruption of vestibulospinal tract activity and hearing loss (pike's peak) over time

Front 15

What type of lesion woudl vestibular neuritis create

Back 15

hypofunctioning, slow phase towards abnormal side

Front 16

Ototoxic drugs can damage the VOR without creating vertigo, how is this possible

Back 16

vertigo only occurs if there is an imbalance between the two systems. Ototoxic drugs would affect both sides equally so you will have sxs of vestibular dysfunction but no vertigo

Front 17

Describe "tornado epilepsy"

Back 17

severe vertigo without vestibular dysfunciton. Disruptions in Heschel's gyrus (primary auditory cortex) prevent preception of equilibrium even though the vestibular system is functioning properly