Vestibular Flashcards
role of vestibular system
head orientation in space, postural stability, gaze stabilization
peripheral vestibular system functions
stabilizing visual images on the fovea of the retina during head movement to allow clear vision
maintaining postural stability
providing info used for spatial orientation
central vestibular system
brainstem processes provide primary control of many vestibular reflexes
- vestibulo-ocular reflex stabilizes images on the retina during head movements
- -posture in static and dynamic activities
- -coordination of limb movements
vestibular system includes
labyrinth CN 8 vestibular nuclei (brainstem, pons)
labyrinth
bony: filled w/perilymph
membranous: filled w/endolymph
- –semicircular canals: head rotation movements
- –otolith organs: acceleration/deceleration (utricle and saccule)
semicircular canals SCC
Function: sense angular head velocity
ampulla - widened end of each SCC
cupula - gelatinous surrounds hair inside ampulla
vestibular hair cells - located in cupula
oriented at 90 to each other (2 floors and floor of room)
hor canal plane is tilted up 30 degrees
ant and post canals 45 degrees off of frontal plane
utricle
oriented horizontally
senses linear acceleration and tilt
saccule
oriented vertically
senses linear acceleration and tilt
otolith organ (in saccule and utricle)
macula-hair cells located
otolithic membrane- gel-like over the macula
otoconia- calcium carbonate crystals on top of otolithic membrane
optokinetic reflex
functions during movement of visual images
smooth pursuits
saccades
smooth pursuits
slower velocities of visual movement; visual tracking
saccades
quick eye movement between 2 targets
cervico-ocular reflex (COR)
eye movement triggered by neck movement, neck proprioceptors send info to brain and then to eyes
vestibulospinal reflex (VSR)
generates appropriate tone to maintain upright position; maintain postural control
vestibulo-ocular reflex (VOR)
functions during movement of head relative to gravity
(therapist passively turns head quickly—eyes should stay fixed)
stabilizes vision during head movement
pd eye movement in opp direction of head movement to maintain image on retina
nystagmus
non-voluntary rhythmic oscillation of the eyes
physiologic nystagmus vs. pathologic nystagmus
oscillopsia
illusion of movement of the visual environment
cause: impaired VOR results in retinal slip
patient complaint: everything bounces when I move, vision is blurry
vestibular dysfunction- peripheral
vestibular neuronitis
labyrinthitis
meniere’s disease - loss of function of cochlear nerve
acousitic neuroma
unilateral or bilateral vestibular hypofunction
BPPV- benign paroxysmal positional vertigo
vestibular dysfunction- central
vestibular migraine MS (nerve degeneration; can affect any nerve) TBI, mTBI, post-concussion cerebellar degeneration cerebellar or vertebral artery infarct arnold-chiari malformation
common vestibular dysfunction complaints
dizziness
sensation of whirling or feeling a tendency to fall
common vestibular dysfunction complaints
vertigo
illusion of movement, sense of environment moving
common vestibular dysfunction complaints
lightheadedness
feeling that fainting is about to occur
common vestibular dysfunction complaints
dysequilibrium
sensation of being off balanced
common vestibular dysfunction complaints
oscillopsia
subjective experience of motion of objects in the visual environment that are known to be stationary
common vestibular dysfunction complaints
red flags
persistent, worsening vertigo and disequilibrium
severe headache
new onset of double vision, cranial palsies, dysarthria, ataxia, incoordination