P Lab: Vestibular System

Question 1

Otoliths

Answer 1

linear accelometer (utricles and saccules)

Question 2

Endolymph

Answer 2

fluid inside the labyinth and the cochlea

High K⁺ and Low Na⁺

Question 3

Vertigo

Answer 3

the feeling that the environment is spinning

Question 4

Linear acceleration

Answer 4

translational acceleration

Question 5

Angular acceleration

Answer 5

rotational

Question 6

Frontal Gaze center

Answer 6

Frontal eye fields in the frontal cortex

Question 7

Paramedian pontine horizantal gaze center

Answer 7

paramedian pontine reticular formation (PPRF)

horzantal saccade generation network

Question 8

Inter-nuclear opthalmoplegia

Answer 8

lesion of the abducens internuclear pathway

Affected eye cannot be adducted (medial rectus palsy)

Question 9

Benign Paroxysmal positional vertigo (BPPV)

Answer 9

feeling of falling backward after inadequate posterior canal stimulation by loose otoconia

Question 10

Meniere’s disease

Answer 10

endolymphatic hyrops

leaking of endolymph onto the vestibule-cochlearnerve leading to K⁺ induced nerve block

Question 11

Labyrinithitis

Answer 11

inflammation of the inner ear (usually viral)

Question 12

Posturography

Answer 12

test of postural stability on a tilt platform

(similar to Romberg test, vestibular funciton, cerebellar function)

Question 13

Rotatory Chiar test

Answer 13

spinning a patient on a rotating chair

test for vestibular and optokinetic function

Question 14

Dix-Hallpike test

Answer 14

the head is rapidly brought down in hanging position

test for BPPV, observe direction of elecited nystagmus

Question 15

Caloric test

Answer 15

cold or warm water irrigation of the external auditory meatus. Nystagmus to the opposite side by cold water, same side by warm water

Question 16

Damage to which part of the ear may cause vertigo?

Answer 16

Labyrinth

Question 17

Damage to which cranial nerve will cause vertigo?

Answer 17

Vestibulo-cohlear nerve

Question 18

Vestibular pathway

Answer 18

Vestibular hair cells -> vestibualr nerve -> vestibular nuclei -> ascending vestibule-ocular pathway in the MLF -> occulomotor nuclei -> extraoccular muscles

Question 19

Which specific pathway mediates horizantal conjugate gaze?

Answer 19

abducens internuclear pathway

Question 20

What is the expected result when performing caloric test on a normal person?

Answer 20

Nystagmus

Question 21

What is the expected result of the caloric test on a comatose patient?

Answer 21

Compensatory deviation of the eyes (slow phase) can be elicited only if the neocortex is affected

No eye movement can be elicited if the brainstem is involved

Cold caloric: conjugate deviation towards the simulated ear is done by the brainstem

In coma, eyes should deviate towards the cold water stimulus but no nystagmus.

Brain dead, eyes will not move at all

Question 22

What is nystagmus mediated by?

Answer 22

The cortex