auditory and vestib Flashcards
discuss auditory pathway from sound waves to inner ear
sound waves - tympanic membrane - middle ear ossicles - oval window - inner ear - vibrations
what are the components of middle ear ossicles
malleus, incus and stapes
malleus is dampened by _____
tensor tympani
stapes is dampened by _____
stapedius muscle
components of inner ear
cochlea
vestibule
semicircular canals
bony labyrinth
bony labyrinth contains
perylimph - structures of membranous labyrinth
comppnents of membranous labyrinth
(cochlear duct, utricle, saccule and semicircular canals)
found w/in membranous labyrinth
endolymph
pathway of vibrations
vibration - scala vestibuli - cochlea - scala tympani - pressure waves - round window
vibration - cochlear duct - organ of corti - basilar memb - spiral gang - cochlear nerve
higher frequency sounds activate hair cells near
apex of the cochlea
discuss path from spinal ganglion
spinal gang - dorsal and ventral cochlear nuc - B brainstem - inf coll - MGB p primary auditory cortex
localize sounds horizontally in space
Superior olivary nuclear complex
crossing auditory fibers
trapezoid body
Lesions in CNS proximal to cochlear nuclei
do not cause unilateral deafness because auditory information crosses bilaterally at multiple points in the brainstem
conductive hearing loss
peripheral lesion in external auditory canal and middle ear
Sensorineural Hearing Loss
Due to cochlea or auditory component of CN VIII
webers test of conductive
louder on affected side
webers on sensorineural
softer on affected side
normal rinne test
sound next to ear should be louder - AC > BC
rinne test of conductive
BC > AC - middle ear bones not workin - softer next to ear
rinne of sensorineural
AC > BC but dec in affected ear
receive input from utricle, anterior saccule and anterior and lateral semicircular canals
sup vestibular gang
receive input from post saccule and psot semicircular canal
inf vestibular gang
discuss pathway of head rotation
head rot = movement of endolymph through ampullae - deforms gelatinous cupula = hair cells (crista ampullaris) - activates vestibular ganglia of Scarpa - vestibular nerves
contains maculae
utricle and saccule for linear accleration and head tilt
contains otoliths
macula
discuss gravity, linear acceleration
pulls on otoliths - activates hair cells - vestbular gang - vestibular div of CN VIII - vestib nuc
for angular acceleration
semicircular canals
for linear acceleration
utricle and saccule - otoliths
for vestibulo ocular reflex
medial vestibular nuc
responsible for VOR
Communication between vestibular nuclei and abducens nerve (LR) on contralateral side and ipsilateral MR - MLF to CN III
discuss VOR
Side to which head turns stimulated the ipsilateral vestibular system greater - ocular motor nuc through MLF
supresses VOR
vestibulocerebellum
triggers physiologic nystagmus
spinning, stripes, endpoint gaze
triggers pathologic nystagmus
lesions in retina, optic nerve/chiasm, brainstem, cerebellum
apparent oscillation of objects viewed
Oscillopsia
sensation of movement, generally a feeling of rotation or spinning of self or the environment
vertigo
Central and peripheral lesions
jerk nystagmus
always vestibular in origin
unidirectional jerk nystagmus
almost always central in origin - brainstem lesion
Acquired bidirectional horizontal nystagmus
may have a rotatory component
pendular nystagmus
inhibited by visual fixaton
peripheral nystagmus
caused by brainstem or cerebellar strokes, neoplasms or multiple sclerosis
acquired pendular nystagmus
short lasting
acquired peripheral nystagmus
long lasting
central nystagmus
spinning or tilting sensation of movement associated with neurologic etiology
True vertigo
generally associated with CV origin
Lightheadedness
Presyncope
gait disorder, orthopedic
neurologic
Disequilibrium
Imbalance
lesion in Inner ear and CN VIII
peripheral vertigo
Brainstem and cerebellum with other focal neurologic deficits (diplopia, visual changes, somatosensory changes, weakness, dysarthria, incoordination)
central vertigo
peripheral head impulse
catch up saccade
central head impulse
no saccade
peripheral nystagmus
uni
central nystagmus
bidirectional
skew of peripheral
no skew
skew of central
vertical skew