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Neuro Dev/Control II > Peripheral Vestibular Hypofunction > Flashcards

Peripheral Vestibular Hypofunction Flashcards

1
Q

Define unilateral and bilateral hypofunction

A
  • Unilateral: has at least 25% reduced vestibular response to bithermal caloric irrigation on one side
  • Bilateral: has abnormal rotational chair gain, phase, & asymmetry
  • Both groups should have normal saccades & smooth pursuit eye movements
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2
Q

Causes of acute unilateral vestibular hypofunction

A
  • Vestibular neuritis (Most common)
  • Trauma
  • Surgical transection
  • Ototoxic medication
  • Meniere’s disease
  • Other lesions of the vestibulocochlear nerve or labyrinth
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3
Q

What is the most common cause of acute spontaneous vertigo

A
  • Acute unilateral vestibular hypofunction
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4
Q

What does acute asymmetry result in

A
  • Imbalance in vestibular tone that manifests with vertigo, nausea, & unsteadiness of gait
  • Spontaneous nystagmus with the fast component beating away from the dysfunctional ear
  • Although nystagmus and vertigo usually subside within hours to 14 days, imbalance and the sensation of dizziness, especially during head movement may persist for many months, or longer, resulting in a more chronic syndrome.
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5
Q

How do you decide whether or not to treat peripheral vestibular hypofunction

A
  • Individuals who have already compensated sufficiently to the vestibular loss and no longer experience symptoms or gait and balance impairments do not need formal vestibular rehabilitation
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6
Q

Exclusions to treating peripheral vestibular hypofunction

A
  • Those at risk for bleeding or cerebrospinal fluid leak
  • Individuals with significantly impaired cognitive function who are likely to have poor carryover of learning.
  • Individuals with very active or frequent vertigo attacks due to Meniere’s disease.
  • Individuals with severe mobility limitations that preclude meaningful application of therapy (they may be less able to participate).
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7
Q

What does COWS stand for

A
  • Cold Opposite Warm Same
  • Used for caloric testing of nystagmus
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8
Q

Factors that modify vestibular rehab outcomes

A
  • Age & gender DON’T affect potential for improvements with VPT
  • Participation results in improved outcomes regardless of time from onset in chronic UVH or BVH
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9
Q

What factors may negatively impact vestibular rehab outcomes

A
  • Anxiety, depression, peripheral neuropathy, migraine, abnormal binocular vision, & abnormal cognition
  • Long term use of vestibular suppressant medication
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10
Q

Medical and surgical management of vestibular dysfunction

A
  • Primary approach for PVH: exercise based
  • Acute stage management after vestibular neuritis or labyrinthitis: vestibular suppressants or antiemetics
  • Surgical or ablative approach limited to patients with recurrent vertigo or fluctuating vestibular function & symptoms not controlled by medications or lifestyle modifications
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11
Q

What conditions are appropriate for ablative/surgical approach

A
  • Meniere’s disease
  • Superior canal dehiscence
  • Perilymphatic fistula
  • Resection of acoustic neuroma (vestibular Schwannoma)
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12
Q

What is the goal of ablative approach

A
  • Convert a fluctuating deficit into a stable deficit to facilitate central vestibular compensation for unilateral vestibular hypofunction (UVH)
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13
Q

What medications may slow the adaptation process in vestibular rehab

A
  • Vestibular suppressants
  • Antihistamines
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14
Q

Diagnosis of unilateral vestibular hypofunction (UVH)

A
  • ENG (elctronystagmography) and VNG (nystagmography): Gold standard
  • Caloric test: best method for determining if UVH is peripheral or central, to identify the side of defect, & measures the velocity of the slow component of nystagmus with cold vs warm irrigation of L/R ear
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15
Q

Lists the other vestibular laboratory tests

A
  • Rotary chair tests: used to Dx BVH
  • Video head impulse test (vHIT)
  • Vestibular evoked myogenic potential test (VEMP): able to assess the integrity of VOR for all semicircular canals
  • Computerized dynamic visual acuity or gaze stabilization tests
  • Computerized dynamic posturography
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16
Q

Describe habituation

A
  • Exercises designed to perform several reps of body movements or watch visual motions that cause mild to moderate symptoms
  • Can use optokinetic stimuli or virtual reality scenarios for visual motion sensitivity
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17
Q

Describe the dynamic visual acuity test

A
  • Perform after a positive HIT
  • Have patient read the smallest line they can on an eye chart with their head stable and straight
  • Perform the test again but now with the patient turning their head while trying to read the letters
  • Positive = off from original line by 3 or more lines & reproduction of symptoms (perform gaze stabilization & habituation exercises)
  • Neg. with symptoms = habituation exercises
  • Neg. and asymptomatic = consider positional testing for BPPV
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18
Q

What does habituation involve

A
  • Repeated exposure to the specific stimulus that provokes dizziness & this systematic repetition of provocative movements leads to a reduction in symptoms over time
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19
Q

What is the general volume of habituation exercises from the Motion Sensitivity Quotient

A
  • Select up to 4 movements from the test & perform 2-3x, 2X/day
  • Perform quickly enough to produce mild/moderate Sx
  • Rest after each movement until Sx resolve (should be <60 sec after each exercise or <15-30 min after all exercises)
  • May take 4 weeks for symptoms to decrease, generally performed for 2 months and then gradually decreased to 1x/day
  • PRECAUTION: NOT FOR PATIENTS WITH ORTHOSTATIC HYPOTENSION
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20
Q

Habituation exercises

A
  • Optokinetic stimuli
  • Virtual reality environments
21
Q

Describe optokinetic stimuli

A
  • Use of repetitive moving patterns & virtual reality immerses patients in realistic, visually challenging environments
22
Q

You can grade the intensity of habituation stimuli through manipulation of

A
  • Velocity
  • Direction of stimulus motion
  • Size/color of stimulus
  • Instructions to the participant
23
Q

Overstimulation prevention guidelines

A
  • Dizziness should return to baseline in no more than 15-30 min
  • If exercise overstimulates, reduce amount, speed, and/or frequency
24
Q

Describe gaze stability

A
  • Adaptation exercises to maximize remaining vestibular function
  • Substitution exercises to promote use of alternative strategies to substitute for missing vestibular function
25
Q

How much is the VOR gain reduced following acute unilateral lesion

A
  • Decreased 75% immediately for head movement toward the affected side
  • Decreased 50% for head movement towards the unaffected side
26
Q

What is the standard test for gaze stability

A
  • Dynamic visual acuity test
27
Q

What does centrally programmed eye movements include

A
  • Compensatory saccades that occur during head movements
28
Q

Describe how dynamic and central programming are used during predictable or unpredictable head movement

A
  • Dynamic visual acuity is improved when patients actively perform the head movement than during unpredictable head movements.
  • Central programming of eye movements may contribute to gaze stability during predictable head movements toward the affected side.
29
Q

Define adaptation

A
  • long-term changes in the neuronal response to head movements with the goal of reducing symptoms and normalizing gaze and postural stability.
30
Q

Define substitution

A
  • goal of promoting alternative strategies (eg, smooth-pursuit eye movements or central pre-programming of eye movements) to substitute for missing vestibular function.
31
Q

Describe VOR x1

A
  • Hold thumb straight out in front of you and shake your head “No” while looking at your thumb
32
Q

Describe VOR x2

A
  • Hold thumb straight out in front of you and turn your head in an “x” diagonal pattern while looking at your thumb
33
Q

Describe VOR x1 with convergence

A
  • Hold thumb straight out in front of you and shake your head “No” while looking at your thumb and begin moving your thumb closer and farther away from your face
34
Q

What systems and strategies contribute to maintaining gaze stability with head movement

A
  • Pursuit and Optokinetic System
  • Cervical-Ocular Reflex
  • Efference Copy: enables the brain to predict the effects of an action (head movement)
  • Anticipatory Intent
  • Central Pre-Programming of Eye Movements
35
Q

Eye movements generated during rapid head impulses in patients with vestibular hypofunction can be categorized as

A
  • Compensatory (i.e., occur during the head impulse)
  • Corrective (i.e., occur after the head impulse): corrective saccades are not really automatic as they depend on intent or vision or both.
  • Non-compensatory (i.e., increase gaze position error).
36
Q

What should vestibular rehab incorporate

A
  • attempts to identify the patients’ preferred gaze-stabilizing strategies and then develop exercises that lead to their recruitment, in particular, compensatory saccades.
37
Q

Describe Overt saccades

A
  • defined as corrective eye movements made after the head comes (substantially) to rest.
  • This is sometimes a little hard to pin down, and to be precise, we will say when head velocity goes through 0 deg/sec.
  • Overt saccades are mainly made after the head is fairly still and visual feedback is available.
38
Q

Describe Covert saccades

A
  • made earlier than head velocity returning to 0, usually during the high velocity part of the head movement.
  • As covert saccades are made prior to the head coming to rest there must be some predictive aspect to them.
  • Covert saccades are difficult to see by an examiner, but can be easily measured with the more rapid response camera technology used in the VHIT test.
  • Covert saccades are desirable because one can see quicker after a head movement
39
Q

Describe substitution

A
  • Central pre-programming of saccades prior to head movement
  • Anticipatory slow phase eye movements prior to head movement
  • Recovery of postural stability by increased reliance of visual and somatosensory cues
  • Pursuit eye movements limited to <1 Hz and a velocity of 60 deg/sec
40
Q

Frequency & duration of treatment recommendations for vestibular hypofunction

A
  • Persons without significant comorbidities that affect mobility and with acute or subacute UVH: x1/wk supervised sessions for 2-3 sessions
  • Chronic UVH: x1/wk supervised sessions for 4-6 wks
  • BVH: x1/wk supervised sessions for 8-12 wks
41
Q

Describe balance and gait exercises

A
  • May involve changes in base of support to increase balance challenge & weight shifting to improve center of gravity control
  • Gait exercises may include varying activities to promote improvement of dynamic control
42
Q

What is the order for the components of balance and gait

A
  • Biomechanics constraints
  • Stability limits/verticality
  • Anticipatory postural adjustments
  • Postural responses
  • Sensory orientation
  • Stability in gait
43
Q

Movement system and vestibular hypofunction

A
  • UVH has a global impact resulting in dysfunctional body strategies: Head-trunk locking or minimization of trunk movements during walking or a rigid trunk
  • The strategies become automatic over time
  • The strategies are counterproductive because symptom-provoking movements are central for recovery from UVHand a flexible body is necessary for optimal balance.
  • Restricted movement can perpetuate dizziness
  • Anxiety and fear can further reinforce problems including those with respiration, which is closely associated with fear and emotions
44
Q

Optimal balance exercise dose for vestibular hypofunction

A
  • Acute/subacute UVH: no specific dose recommendations
  • Chronic UVH: minimum of 20 min daily for at least 4-6 wks
  • BVH: 6-9 wks
45
Q

How do we dose balance training interventions?

A
  • The RPD scores correlated with the magnitude of postural sway, suggesting that they can be used as a proxy measure of perceived intensity of balance exercises.
46
Q

How to facilitate postural stability

A
  • Facilitate using visual and/or somatosensory cues to substitute for impaired vestibular function
47
Q

Considerations for balance and gait training

A
  • Reduce/eliminate visual cues and/or make somatosensory cues inaccurate
  • Static postures vs dynamic movements
  • Changes in base of support
  • Weight shifts
  • Head turns
  • Complex visual environments
  • Secondary (dual) tasks
48
Q

General conditioning for peripheral vestibular hypofunction

A
  • General conditioning, such as walking for endurance or aerobic exercise, is frequently an element of rehabilitation because people with peripheral vestibular dysfunction often limit physical activity to avoid symptom provocation.
  • General conditioning exercise (eg, stationary bicycle) by itself has not been found to be beneficial in patients with vestibular hypofunction
49
Q

Reasons for stopping therapy for peripheral vestibular hypofuction discharge planning

A
  • Achievement of primary goals
  • Resolution of symptoms
  • Normalized balance & vestibular function
  • Plateau in progress

Neuro Dev/Control II (19 decks)

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