L3 Vestibular Dysfunction Flashcards
What are the functions of the vestibular system?
postural control
eye-head coordination
perception of orientation in space
What might vestibular dysfunction present like?
-unsteadiness
-dizziness
-misperceptions about where the body or head are in space
-difficulty in visually busy environments, dimly lit environments, walking on uneven surfaces
Semicircular canals purpose is
rotational movement
receptor organ is the ampulla, which is filled with endolymph fluid, that will move the hair cell dependent on the movementV
Vestibule purpose is
linear movement
receptor organ is the macula, which has otoliths that can become dislodged. has a gelatinous layer, which provides reliable info with movements
Pairings of Semicircular Canals
Left Posterior & Right Anterior
Left Anterior & Right Posterior
Portions of the vestibule
saccule and utricule
Action Potential of Vestibular System
baseline firing rate is present; always firing
turning head will increase the action potentials in the CN VIII on the same side, while decreasing the firing rate on the opposite nerve
medial and superior vestibular nuclei
MLF fibers from these nuclei synapse on oculomotor, trochlear, and abducens nuclei
assist in coordination, maintaining posture and modulating vestibular reflexes
Lateral vestibular nucleus
gives rise to the lateral vestibulospinal tract
helps with maintaining balance and extensor tone
Medial and inferior vestibular nuclei
give rise to the medial vestibulospinal tract
controls head and neck positioning
VOR –Vestibulo-ocular reflex
- Peripheral reflex that maintains gaze stability
- Generates a compensatory eye movement in response to head movement to keep visual environment stable when head is in motion
- The peripheral vestibular system provides info that allows the eyes to respond with equal and opposite movements when the head moves
Intact system and VOR
the vestibulocerebellum can enable visual fixation to overcome the VOR
allows eyes to move with the head
Gain = 1:1 meaning
every degree of head movement, there is an equal and opposite movement at the eyes
Dizziness
vague term used by patients to describe many different abnormal sensations
can include light-headedness, faintness, nausea, unsteadiness, orthostatic hypotension
Vertigo
spinning sensation of movement
1. typically more indicative of vestibular disease
2. can be caused by lesions anywhere in vestibular pathway
3. most cases are peripheral disorders, involving inner ear
Patient education with vestibular disorders
patient ed is INTEGRAL
1. take time to explain differences in dizziness, lightheadeness, true room spinning
2. explain that provoking is a part of the exam
3. ensure someone can drive them
4. ensure patient hasn’t taken meds that would impact exam
Dizziness Handicap Inventory
measures the patient’s perception of their handicap
Y/N Questions, deciding on perception of their disability
Activities-specific Balance Confidence Scale
measures confidence in performing 16 functional daily acitivites without LOB or fear of falling
score <67% indicates increased risk of falling
Medications that can lead to temporary dizziness
antihistamines, benzos, alpha/beta agonists, antidepressants, aspirin, calcium channel blockers, diruretics, alcohol
Peripheral vestibular pathology
affecting the vestibular organs or vestibular nerves
can be unilateral or bilateral
Benign Paroxysmal Positional Vertigo (BPPV)
subset of peripheral, involving displacement of otoconia from the utricle and travel into semicircular canals
Central Vestibular Disorders
affecting the brainstem, areas of teh cortex that process vestibular information, or cerebellum
Peripheral Vestibular Pathologies Names
meniere’s
vestibular neuritis
vestibular labyrinthitis
acoustic neuroma
ototoxicity
perilymphatic fistula
superior canal dehiscence
BPPV S/S
onset = sudden and correlates with movement
Intensity of vertigo = severe
Duration of vertigo = 30s - 2min
CNS findings = none
Hearing loss = none
Oculomotor = normal
Nystagmus = torsional with direction
Peripheral Bilateral Vestibular Hypofunction
onset = sudden and following an illness, but can be gradual
Intensity of vertigo = absent
Duration of vertigo = absent
infrequent nausea
Hearing loss = tinnitus
Nystagmus = none
Peripheral Unilateral Vestibular Hypofunction
onset = sudden, following illness, can be gradual
Intensity of vertigo = severe
Duration of vertigo = episodic
frequent nausea
Hearing loss = tinnitus
Nystagmus = horizontal with fast beat away from involved side
Meniere’s DIsease
progressive problem with high pressure of inner ear fluid that most often leads to vertigo spells and hearing loss
-low frequency hearing loss
-fluctuating hearing loss, pressure in ear, innitus
-spells of vertigo that are minutes to hours, with nausea and imbalance
Vestibular Neuritis
inner ear infection that is typically caused by a virus
sudden onset
duration of vertigo is hours to days
nausea
no hearing loss
usually single event
Acoustic Neuroma
nerve sheath tumor found in internal auditory canal
asymmetrical hearing loss
tinnitus
vertigo
Ototoxicity
bilateral peripheral pathology due to damage of hair cells, usually after antibiotics
unsteadiness, vertigo is absent, may include hearing loss, objects appear to jump
Central Vestibular Pathologies
stroke
TBI
MS
Tumor
Degenerative cerebellar disorders
Central Vestibular Dysfunction
can be caused by damage to any of CNS cestibular structures
onset: depends on etiology
Intensity of dizziness: longer duration or constant
Nystagmus = vertical resting, will not fatigue with testing, changes direction
Non-vestibular causes for dizziness
anxiety
cardiac arrhythmias
diplopia
headache
medication
orthostatic hypotension
alcohol
Medical Exam for Vestibular Dysfunction includes
rotary chair
bithermal caloric testing
MRI or CT scan
Video oculography
Rotary Chair
patient is positioned in specialized chair with video goggles to monitor eye movement as chair is positioned differently
performed by audiologist
Bithermal caloric testing
uses differences in temperature to diagnose damge to CNVIII
the test SHOULD produce nystagmus
Objective Exam for Vestibular
- Screen the cervical ROM
- Screen vertebrobasilar insufficiency
- Begin objective tests
VBI Testing
-artery supplies cirulation to the brain and compression of these vessels can be life threatening
-includes cervical rotation to L/R for 10 s, head and body psition that provokes S/s
what to look for when testing VBI
diploplia, dizzines, dysarthria, drop attacks, dysphagia
nausea, numbness, nystagmus
Nystagmus
involuntary and rhythmic rapid eye movements
includes fast phase of movement in one direction and slow phase in other
Peripheral nystagmus
the fast beat is away from the side of the lesion and does not change direction
will begin to decrease over time due to central compensation and might be suppressed with gaze fixation
IF there are central nervous system signs or suspected CNS dysfunction with no underlying diagnosis
this warrants and IMMEDIATE REFERRAL back to physician
Potential findings on non-vestibular dysfunction
elevated HR/RR
abnormal BP to position changes
Possible findings with Central Vestibular dysfunction
+ VOR cancellation
abnormal saccades (overshoot)
abnormal smooth pursuit (saccadic intrusions)
UVH Possible findings
+head impulse test
+head shaking nystagmus
+DVA
BVH Possible Findings
+head impulse test, bilaterally
+head shaking nystagmus
+DVA
will not see nystagmus if there is symmetric loss
