P Lab: Vestibular System Flashcards
Otoliths
linear accelometer (utricles and saccules)
Endolymph
fluid inside the labyinth and the cochlea
High K+ and Low Na+
Vertigo
the feeling that the environment is spinning
Linear acceleration
translational acceleration
Angular acceleration
rotational
Frontal Gaze center
Frontal eye fields in the frontal cortex
Paramedian pontine horizantal gaze center
paramedian pontine reticular formation (PPRF)
horzantal saccade generation network
Inter-nuclear opthalmoplegia
lesion of the abducens internuclear pathway
Affected eye cannot be adducted (medial rectus palsy)
Benign Paroxysmal positional vertigo (BPPV)
feeling of falling backward after inadequate posterior canal stimulation by loose otoconia
Meniere’s disease
endolymphatic hyrops
leaking of endolymph onto the vestibule-cochlearnerve leading to K+ induced nerve block
Labyrinithitis
inflammation of the inner ear (usually viral)
Posturography
test of postural stability on a tilt platform
(similar to Romberg test, vestibular funciton, cerebellar function)
Rotatory Chiar test
spinning a patient on a rotating chair
test for vestibular and optokinetic function
Dix-Hallpike test
the head is rapidly brought down in hanging position
test for BPPV, observe direction of elecited nystagmus
Caloric test
cold or warm water irrigation of the external auditory meatus. Nystagmus to the opposite side by cold water, same side by warm water
Damage to which part of the ear may cause vertigo?
Labyrinth
Damage to which cranial nerve will cause vertigo?
Vestibulo-cohlear nerve
Vestibular pathway
Vestibular hair cells -> vestibualr nerve -> vestibular nuclei -> ascending vestibule-ocular pathway in the MLF -> occulomotor nuclei -> extraoccular muscles
Which specific pathway mediates horizantal conjugate gaze?
abducens internuclear pathway
What is the expected result when performing caloric test on a normal person?
Nystagmus
What is the expected result of the caloric test on a comatose patient?
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
What is nystagmus mediated by?
The cortex
