Lecture 12 Flashcards
vestibular system function
maintain equilibrium/postural control
primary input to the vestibular nuclei
- peripheral vestibular system - inner ear/CN 8 pathways
- visual pathways
- proprioceptive/mechanosensory pathways
central vestibular pathways
located in midbrain at junction of pons and medulla
vestibular nuclei process all vestibular input and coordinate all vestibular responses through connections to other areas of the CNS
peripheral vestibular system
inner ear R/L - semicircular canals - otolithic organs: utricle and sccule
vestibulocochlear nerve (CN8) - transits vestibular information from inner ear to the vestibular nuclei
bony labyrinth
convoluted space located with petrous portion of temporal bone
contains: perilymphatic fluid similar to CSF, auditory structure = cochlea, vestibular structures = semicircular canals: 3 in each ear, otolithic organs (utricule, saccule)
membranous labyrinth
contains membranous portions of the 3 semicircular canals, as well as the utricle and saccule
filled with endolymph-resembles intracellular fluid
vestibular structures
semicircular canals: horizontal, posterior, anterior
otolithic organs: utricle, saccule
semicircular canals
three semicircular canals lay in three different plans and are arranged perpendicular to each other in each ear
1. horizontal
2. posterior
3. anterior (superior)
function of semicircular canals
monitor ROTATIONAL acceleration/deceleration movement - “speed” of rotational movement
receptors of semicircular canals
ampulla - enlarged area that contains recpetors in each semicircular cancal
the receptors are hair cells that emerge from crista ampullaris
the hair cells embedded in a gelatinous mass known as the cupula
hair cells are connected to CN 8
endolymph - fluid in the semicircular canals
rotation of head causes endolymph to shift in the semicircular canal and “bend” (displace) the cupula
the change in cupula position bends (moves) the hair cells which stimulates an action potential in vestibular nerve
movement in all three canals allows the brain to determine the axis and speed of rotation
semicircular canals coplaner pairs
horizontal canals work together
L posterior and R anterior work together
R posterior and L anterior work together
otolithic organs: utricle and saccule function
head movement and linear acceleration/deceleration
changing head position tilts the macula causing the otoliths to shift and displace the gel layer
the change in gel layer bends (moves) the hair cells which stimulates an action potential in vestibular nerve
otolithic organs: utricle and saccule location
located within the vestiule of each membranous labyrinth
located almost perpendicular to each other
saccule: vertical
uticle: horizontal
macula
recepetors in utricle and saccule
structure: hair cells embedded in a layer of gell like substance, otoliths (ear stones) small, granular-like crystaks that lay on top of the gel layer
otolithic organs: utricle
located in the vestibule
contains receptors known as macula
endolymph flows in the bony labyrinth
slightly superior and lateral to saccule
linear movement -> anterior/posterior - like a car in traffic
lies horizontally, hair cells on floor
utricle function
monitor head position and linear acceleration/deceleration
they DO NOT monitor rotation
otolithic organs: saccule
located in the vestibule
slightly inferior to utricle
contain recpetors known as macula
endolymph flows in the bony labyrinth
vertically oriented - hair cells located on medial wall
senses vertical acceleration (still linear) - like an elevator
saccule function
monitor head position and linear acceleration/deceleration
they DO NOT monitor rotation
semicircular canals
monitor rotational acceleration/deceleration of head
otolithic organs - utricle and saccule
monitor head position and linear acceleration/deceleration of head
Benign Paroxysmal Positional Vertigo (BPPV)
peripheral vestibular disorder
most common peripheral vestibular disorder
most common cause of vertigo in adults
symptoms of BPPV
acute/sudden onset of vertigo and nystagmus
paroxysmal - sudden
onset/duration of BPPV
sudden onset that lasts seconds to minutes (1-2)
BPPV incidence and risk factors
affected women outnumber men by a ration of 1.6:1
peak age of onset in the 6th decade of life
low vitamin D levels associated with recurrence
BPPV causes
idiopathic: 50-70%
head trauma: 7-17% - more common to have more than one canal involved
BPPV etiology
otoliths dislodge from the macular of the utricle/sacule & travel to semicircular canal
the otoliths accumulate near the cupula and disrupt the endolymph flow/hair receptor signaling which causes vertigo nystagmus, etc.
*most common cause of BPPV is accumulation of otoliths in posterior semicircular canal
*may occur spontaneously or after head trauma or infection (upper respiratory illness)
posterior>horizontal>anterior
canalithiasis
otoliths accumulate in endolympth near in semicircular canal, generally near cupula
free flowing otoconia in semicircular canal - delay of onset of symptoms - symptoms less than 60 seconds
cupulolithiasis
otoliths accumulate (get stuck) in cupula
otoconia adhered to cupula - no delay in symptoms with testing - symptoms more than 60 seconds
nystagmus
rapid, uncontrollable eye movements, generally bilaterally
occuring in multiple directions
side to side: horizontal
up and down: vertical
in a circle: torsional or rotary
dix-hallpike/test
procedure to assess for posterior canal BPPV
- pt seated, rotate head 45 degrees
- safely, passively and quickly bring pt into supine with head extended 30 degrees
- observe for nystagmus or complaint of vertigo
- testing ear that is down
- position creates an abnormal or mismatch of semicircular canal signaling between coplaner pair between non-involved side and the involved side with the displaced otoliths
- the abnormal/mismatch of vestibular signaling stimulates nystagmus and vertigo symptoms
dix-hallpike test results
- “positive test” if maneuver provokes nystagmus that is upbeating and torsional to the side involved and pt complains of vertigo or “dizziness”
slight delay in symptom onset = latency
symptoms typically last 5-30 seconds = duration - negative test if no symptoms reported, no nystagmus observed
BPPV treatment
particle repositioning maneuvers (PRM)
- repositioning of patient in an attmept to redirect fluid flow in the posterior semicircular canal in such a way that the otoliths are “released” and flow back to macula
- several variants of PRM, including the Epley maneuver, Semont maneuver, and many others
Meniere’s Disease
peripheral vestibular disorder
symptoms: sensation of fullness/hearing loss, tinnitus, vertigo, +/- nausea, and vomiting
onset/duration: slow chronic onset, lasts for 2-3 days with gradual improvement over 2 weeks
meniere’s disease etiology
not completely understood
associated with abnormal endolymph fluid pressures within inner ear
low sodium diets are often used to manage
*PT does not treat
40 to 60 yr old age group, nearly 1:1 male:female
familial occurrence - autosomal-dominant
vestibular hypofunction
can occur unilateral (more common) or bilaterally
due to infection, trauma, vascular events
Unilateral Vestibular Hypofunction (UVH)
- due to mismatch in firing between coplainer pairs
- vestibular neuritis
- labyrinthitis
vestibular neuritis
acute unilateral vestibulopathy is the second most common cause of vertigo
viral infection is common and usully affects the vestibular nerve unilaterally
absense of cochlear involvement - normal hearing
presence of vestibular symptoms: dizziness/vertigo, nausea, vomiting
onset of vestibular symptoms are often about 2 weeks post infection
vestibular neuritis treatment
medications: antihistamines, anticholinergic agents, antidopaminergic agents, steroids, antivirals
glucocorticoids administered within 3 days after onset of vestibular neuronitis improves long-time recovery of vestibular function and reduces length of hospital stay
symptom resolution over 6 weeks to 3 months
labyrinthitis
inflammation of the membranous labyrinth
due to infection bacterial or viral
causes inflammation to BOTH branches of CN 8
- changes in hearing, vertiginous symptoms: dizziness, imbalance, vertigo
labyrinthitis treatment
medications: steroids, antiemetics-symptom management
glucocorticoids administered within 3 days after onset of vestibular neuronitis improves long-time recovery of vestibular function and reduces length of hospital stay
prognosis: symptoms should resolve within days to weeks
perilymphatic fistula
an abnormal communication of the inner and middle ear spaces - causing vertigo
vestibular symptoms or hearing loss may be major presenting complaint
more common with conenital malformations or prior ear surgery
damage can also result from an increase in the pressure of the CSF
easing of symptoms at rest and increase with activity
sensorineural hearing loss
