vestibular Flashcards
what are the 2 major organs of the vestibular system
vestibule and SCC
what structures are in the vestibule
saccule and utricle
purpose of the vestibule
- respond to linear movements
- respond to displacement to gravity
-respond to linear acceleration
SCC structures
anterior, posterior and horizontal
what do the SCC respond to
- head rotational movements
- acceleration
Vestibulochochlear nerve CN 8
1) vestibular branch: balance (SCC, vestibule)
2) cochlear branch: auditory
major functions of the vestibular system
- maintenance of balance and stable posture
- postural reflexes that respond to unexpected perturbation
- a stabilizer, acting to counteract the effect of body movement, gravity and other external forces
what do the SCC contain
- crista ampullaris or ampulla
- cupula
how are the cupula stimulated
- rotation of the head
if the head is rotated to the right
- cupula moves to the left
- sterocilia are bent
- cilia send excitatory signals
- the firing rate of the right vestibular nerve increases and the left firing rate of the vestibular nerve decreases
the push - pull phenomenon
- if there is a change in firing rate with head movement tells the brain what movement has occured
- increase of firing rate on the same side of the head movement
- SCC work in their functional pairs
The SCC functional pairs
- HSCC: horizontals with eachother
- RALP: right anterior left posterior
- LARP: left anterior right posterior
where are the otoliths contained
in the macula
what accelerations do the saccule respond to
up and down and forward and backwards
what accelerations do the utricle respond to
sideways acceleration and forward and backwards
what do the ototliths provide information for
body position with reference to force of gravity and linear acceleration
what do the stereocilia respond to when the head is forward
changes in gravity and tilt, displacement of the otoliths and sending off sensory signals
where are the vestibular nuclei located
on each side of the brainstem in the junction of the pons, medulla, and near the 4th ventricle
what does the medial longitudinal fasciculus connect
the vestibular nuclei to the cranial nerves (3,4,6)
- helped bring out coordinated movements of the eyes through VOR
Vestibular Ocular Reflex (VOR)
necessary for stabilizing vision; pts whose VOR is impaired find it difficult to read, dizziness, and difficult to drive (turning head)
what tract does the VOR use
the medial longitudinal fasciculus
VOR rotation to the right
excitation: left abducens and right rectus medialis
inhibition: left medial rectus and right abducens
what vestibular nucleus gives rise to the lateral vestibular tract
the lateral vestibular nucleus
what does the lateral vestibular tract receive info form
otoliths, cerebellum, and vestibulocerebellum
where does the lateral vestubulospinal tract terminate
the AHC of the ipsilateral side
what is the action of the lateral vestibulospinal tract
lower limb extensors
lumbar back musculature
what vestibular nucleus does the medial vestibulospinal tract arise from
the medial vestibular nucleus
what does the medial vestibulospinal tract get information from
the inferior vestibular nucleus and SCC
where does the medial vestibulospinal tract terminate
AHC on of ipsilateral side in C spine
what is the action of the medial vestibular nucleus
- role in head motion, posture, and stable eye movement
- cervical and upper T spine musculature
Vestibulocerebellar connection
- vestibular nucleus to the flocculonodular nobe
- coordinate movement to calculate posture and balance control
vestibulo-thalamo-cortical pathways
provides conscious awareness of head position/movement and input to the corticospinal tracts (spatial orientation)
vestibuloocular pathway
controls the magnitude of muscle responses to vestibular information, including the grain of the VOR. key pathway for rehabilitation of a pt.
onset of nystagmus in peripheral lesion
delayed
onset of nystagmus in central lesion
immediate or delayed
characteristics of nystagmus in peripheral
- horizontal or rotatory. NOT vertical
- Does NOT change directions
- nystagmus ONLY if vertigo is present
characteristics of nystagmus in central
- horizontal, rotatory or vertical
- nystagmus can change directions
- nystagmus in the absence of vertigo
symptoms of central lesion
the 4 Ds
- Diplopia: double vision
- dysphagia: trouble swallowing
- dysarthria: speaking
- dysmetria: incoordination
abnormal eye tracking
hearing loss
change in consciousness
new onset of nystagmus
symptoms of peripheral lesion
- notable onset of vertigo often described as dizziness
Cervicogenic
- associated with cervical trauma or injury
- symptoms with moving the body on the head
- impacts of the VOR and DVA
3 categories of vestibular disorders (peripheral)
- deficiency
- distortion
- fluctuation
diagnosis of deficiency
- neuronitis/labyrinthitis (viral infaction)
- acoustic neuroma (tumor in ear)
symptoms of deficiency
- new onset
- often severe
- complaints of unsteadiness
- instability
- intense spinning
- inability to walk
- difficulty with vision
distortion diagnosis
Benign Paroxysmal Position Vertigo (BPPV)
general symptoms of Distortion
- vertigo
- instability increases in the presence of inappropriate sensory signals (particularly vision (elderly)
fluctuation diagnosis
menieres disease, migraine associated with dizziness and vertigo
BPPV what is it
it is a mechanical disorder, caused by otoconia being displaced from the macula of the utricle into the SCC
- canalithiasis or cupulolithiasis
- it is the most common cause of vertigo due to peripheral vestibular disorder
- brief episodes of vertigo when the head is moved into one of the 5 positions
- common in older adults
5 head movements that elicit BPPV symptoms
1) turning over in bed
2) lying down
3) rising up in supine
4) bending forward
5) reclining head
ways to examine by providing maneuvers
- Dix Hallpike
- Epley Manuever
disequilibrium of aging
- no single causative factor
- multiple small summating factors including
1) declining sensory input or inputs
2) declining sensory processing by the CNS
3) decreased control mechanisms for balance
4) asking musculoskeletal system (decreases ROM and strength)
multisensory disequilibrium
- combined function of vestibular, visual and somatosensory systems
- any combination of disorders that impair all 3 sensory systems
symptoms of mulitsensory disquilibrium
- disequilibrium when walking especially in dim lighting and uneven surfaces
- sensory complaints such as numbness and tingling in feet
- poor proprioception/vibratory sensation or use of SOM
- poor use of vestibular system
- poor vision
menieres disease
- the triad: tinnitus, hearing loss, aural fullness
- episodes of severe vertigo with N/V
- hearing loss at low frequencies
- complaints of pressure or fullness in head
- may be congenital do to an old ear infection effecting the endolympthatic sac
patho-mechanism of menieres disease
increase volume of endolymph eventually leading to disruption of ionic balance between endolymph and perilymph which results in spontaneous activation of vestibular receptors unrelated to had movement
Deficiency: unilateral vestibular loss acute
- imbalance
- assistance with gait
- complaints of blurred vision with head movement
- nystagmus and vertigo
- vertical diplopia
- romburg unable to do sharpened
- cannot walk with head movements
Deficiency: Unilateral Vestibular Loss chronic
- decreases head movement and activity
- decreased endurance
- visual dependance
- blurred vision with head movement
- rhomburg + sharpened
- normal gait
- need vestibular rehab
UVL from Acoustic Neuroma pathology
- cerebello-pontine angle neoplasm
- gradual onset
- surgical resection of tumor usually resulting in damage to cerebellum and vestibular nerve
symptoms of UVL
(mixed peripheral and central)
- unilateral hearing loss
- disequilibrium with head movement
- veering
- tinnitus
Structures supplies by the anterior inferior cerebellar artery
- vestibular nuclei
- trig nuclei
- CN 5
- CN 7
- anterolateral tract
symptoms associated with AICA
(mixed peripheral and central vestibular problems)
- Labyrinth (vertigo, tinnitus and hearing loss)
- Vestibular nuclei and nerve
- cerebellar flocculus and MCP (dysmetria and ataxia)
symptoms associated with PICA
also called wallenburg’s syndrome or lateral medullary infarction (mostly vertebral artery)
- vestibular nuclei (vertigo, lateropulsion, disequilibrium)
- cerebellum (dysmetria and gait ataxia)
- anterolateral tract (contralateral reduced pain and temperature of body)
- CN 5 (decrease pain and temp on face)
- solitary and vagus centers in the medulla (vomiting and nausea)
input to the vestibular system
- Labyrinthine (inner ear) activity
- Proprioception and superficial sensation
- Vision
- cortex , cerebellum, reticular formation, extrapyramidal system
outputs from the vestibular system
- Cortical awareness of head body, and motion
- Control of oculomotor activity
- Control of posture
- Control of motor skills and coordination
deficiency : unilateral vestibular loss (UVL) acute
- less then 3 days
- imbalance
- assistance with gait
- increased imbalance with head movement
- complaints of blurred vision with head movement
- nystagmus and vertigo
- vertical diplopia
- positive Romberg and unable to sharpen
- unable SLS
- can’t walk with head movements
deficiency: unilateral vestibular loss (UVL) chronic
- more then 3 days
- decreases head movement and activity
- decreases endurance
- visual dependence
- blurred vision with head movement
- romberg + sharpened
- normal gait
- SOT might be ok
- NEEDS VEST REHAB
distortion: disequilibrium of aging
- no single causative factor
- Disequilibrium on the bases of multiple small stimulating factors (declining sensory, declining balance, aging MS system)
- gradual worsening of symptoms
- most common symptom is disequilibrium when walking
distortion: multi sensory disequilibrium
- Refers to the combined dysfunction of vest, vision, and somatosensory systems
- ex diabetes can cause neuropathy, retinopathy and peripheral neuropathy
distortion: multi sensory disequilibrium symptoms
- disequilibrium when walking especially in dim lighting and uneven surfaces
- sensory complaints such as numbness and tingling in feet
- poor proprioceptive/vibratory sensation or use of SOM
- poor use of vestibular system
- poor vision
