Vestibular Testing

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Vestibular Testing

Otology/Audiology
Author Credentials 

James Naples, MD
Clinical Instructor 
Division of Otolaryngology
Beth Israel Deaconess Medical Center, Harvard Medical School
Boston, MA

Sherrie Davis, AuD
Department of Audiology
University of Pennsylvania
Philadelphia, PA 

Isaac Erbele, MD
Fellow
Hearing and Balance Center, Our Lady of the Lake Regional Medical Center
Louisiana State University Health Sciences Center
Baton Rouge, LA

Module Summary

This module outlines the tests necessary as part of a comprehensive vestibular assessment. It addresses the role of vestibular testing in evaluating both the central and peripheral vestibular systems. Various tests are described and detail is provided on how each test can be used by the clinician to identify a potential location insult and etiology of symptoms. The module commences with case studies of common vestibular pathologies and how testing is applied in these situations.

Module Learning Objectives 
  1. Choose appropriate vestibular testing for patient diagnosis and management. 
  2. Recognize how each vestibular test evaluates the function of specific anatomy or anatomical pathways within the peripheral and/or central vestibular system. 
  3. Review the history and bedside vestibular tests necessary to thoroughly evaluate patients with dizziness and vertigo.
  4. Describe the role of comprehensive vestibular diagnostic testing in the diagnosis of central and peripheral vestibular disorders.  
  5. Recognize that medications and neuro-otological surgical interventions may influence vestibular testing results and anticipate specific changes on testing based on these intervention.

 

Anatomy

Learning Objectives 
  1. Understand how vestibular testing localizes lesions to specific anatomical sites (peripheral vs central)
  2. Identify innervation of semicircular canals and otolith organs
    • Lateral, Superior canals, utricle → Superior vestibular nerve
    • Posterior canal, saccule → inferior vestibular nerve
  3. Predict eye movement from stimulation of each semicircular canal
    • Nystagmus named by fast phase
    • Nystagmus measured by velocity of slow phase
  4. Discuss acceleration forces encoded by each otolith organ
    • Semicricular canals: angular acceleration (yaw, pitch, roll)
    • Saccule: verticle/gravitational acceleration forces
    • Utricle: Horiztonal/translational acceleration forced
  5. Describe the reflex arc of horizontal vestibulo-ocular reflex (VOR), saccule to sternocleidomastoid, and utricle to inferior oblique  
  6. Name the four major vestibular nuclei
    • Superior
    • Inferior
    • Lateral
    • Medial
  7. Describe principal afferent and efferent innervation of the vestibular nuclei

 

Spontaneous Nystagmus: If present, can suggest peripheral or central anatomical lesion. Fixation/light will suppress nystagmus caused by peripheral lesion. Central nystagmus will not suppress in these settings.

Gaze-evoked Nystagmus: Abnormality suggests ipsilateral lesion at cerebellopontine angle (CPA); Can be drug-induced central lesion.

Positional Nystagmus: The direction and fatigability of nystagmus in Dix-Hallpike position can indicate peripheral vs central lesion. Direction of the nystagmus can suggest which canal is affected in BPPV.  Downbeating nystagmus and nystagmus that does not fatigue localizes a central source.

Caloric Testing: Stimulates endolymph flow of lateral semicircular canal → indirect evaluation of superior vestibular nerve.

cVEMP: Measurement of saccular response → inferior vestibular nerve.

oVEMP: Measurement of utricular response → superior vestibular nerve.

Saccadic Eye Movements, Smooth Pursuits, Optokinetic Nystagmus: These tests represent evaluations of the central nervous system, and abnormalities in these tests suggest central pathology.

Rotational Chair Gain, Asymmetry, Phase: Peripheral lesions usually suggested by decrease in Gain and Phase lead.  More diverse patterns seen in central lesions.

 

 

References 
  1. Baloh RW, Honrubia V, Kerber KA, editors.  Baloh and Honrubia’s Clinical Neurophysiology of the Vestibular System.  New York: Oxford University Press; 2011.
  2. Merchant SN, Nadol JB.  Schuknecht’s Pathology of the Ear, 3e.  Samford, CT: People’s Medical Publishing House; 2010.
  3. Nager G. Pathology of the Ear and Temporal Bone. Baltimore, MD: Williams & Wilkins; 1993.
  4. Schwartz DWF, Tomlinson RD. Chapter 4: Physiology of the Vestibular System. In Neurotology, 2e. Ed. By Jackler RK and Brackmann DE. Philadelphia: Mosby, Inc; 2005

 

Basic Science

Learning Objectives 

Caloric Testing 

  1. Compare endolymphatic fluid movement caused by introducing warm air versus cold air to the external auditory canal
    • Warm: Induces “ampullopetal” (cupular deviation towards utricle) response
    • Cold: Induces “ampullofugal,” (cupular deviation away from utricle) responses 
  2. Define vestibulo-ocular reflex (VOR) and understand “velocity storage” as it relates to the VOR
    • VOR is reflex elicited from vestibular end organ that activates extraocular muscles 
    • VOR coordinates head, eye, and body position in space
    • Velocity storage maintains response to vestibular stimuli after decay of stimuli
  3. Define “gain” as it is related to eye movements resulting from rotational movement of the head
    • Gain = ratio of eye movement to head movement
    • In ideal situation Gain = 1
  4. Predict gain as a result of unilateral vestibular loss
    • In vestibular loss Gain < 1
  5. Define “compensation,” as related to vestibular loss
  6. Analyze the difference in tracking an object using smooth pursuit, the VOR, and the optokinetic system

 

References 
  1. Baloh RW, Honrubia V, Kerber KA, editors.  Baloh and Honrubia’s Clinical Neurophysiology of the Vestibular System.  New York: Oxford University Press; 2011.
  2. Schwartz DWF, Tomlinson RD. Chapter 4: Physiology of the Vestibular System. In Neurotology, 2e. Ed. By Jackler RK and Brackmann DE. Philadelphia: Mosby, Inc; 2005

 

Patient Evaluation

Learning Objectives 
  1. Describe the role vestibular diagnostic studies and bedside vestibular exam in the diagnosis of central and peripheral vestibular disorders
    • Bedside Exam
      • Otoscopic Exam
      • Tuning Fork Exam- Weber and Rinne (512Hz)
      • Cranial Nerve Exam
      • Comprehensive Neurological Exam
      • Head-Impulse Test (HIT)- catch up saccade suggests peripheral insult
      • Romberg/ Finger-to-Nose Test- evaluation of cerebellar function
      • Dix-Hallpike positioning
    • Neurotologic history
      • Description of symptoms – true vertigo, unsteadiness, lightheadedness
      • Duration & frequency of symptoms 
      • Prodrome, triggers, concurrent symptoms 
      • Otologic/audiologic history
      • Migraine history for self and/or family
      • Additional comorbidities and medications
    • Audiologic Assessment 
      • Air conduction and bone conduction pure tone testing and complete speech audiometry needed – vestibular disorders commonly occur concurrently with auditory abnormalities (Meniere’s disease, labyrinthitis, vestibular schwanomma)
      • Tympanometry to ensure an intact tympanic membrane for caloric studies
    • Oculomotor Studies
      • Utilizes eye movement recordings to evaluate central vestibular pathways. Commonly performed as part of Videonystagmography (VNG) 
      • Gaze-evoked nystagmus – evaluates if the patient can maintain gaze without eye drifting or the elicitation of nystagmus
        • Central, Lateral and Vertical gaze conditions
          • Direction and degree of nystagmus documented
          • Avoid elicitation of end-point nystagmus
          • Rule-out pre-existing extra-ocular muscle abnormalities as contributory 
      • Random Saccade Testing
        • Evaluates the patient’s ability to use rapid eye movements to re-fixate on a target that has moved
        • Targets are randomized for time and location
        • Binocular assessment of velocity, accuracy and latency of random saccades
        • Patterns of abnormality correlate with abnormalities in the cerebellum and/or brainstem
          • Clinical correlation with radiographic studies
          • Can seem abnormal because of inattention – may need to be repeated to ensure best performance
      • Smooth Pursuit Test
        • ​Assessment of the patient’s ability to track an object that is moving continuously by using single smooth eye movement
        • Target is moved in a sinusoidal fashion at varying speeds
        • Gain objectively measured at multiple sinusoidal frequencies
        • Morphology of smooth pursuit- subjective assessment whether the patient’s eye movements were fluid and smooth or if they were saccadic, consisting of small jerky movements to track the target
        • Ability to smoothly pursue declines with age – pursuit that is somewhat saccadic may be age appropriate
        • True abnormalities suggest involvement in the brainstem and/or cerebellum
          • Testing should be repeated to perform best possible performance
      • Optokinetic Testing
        • Production and measurement of optokinetic nystagmus (OKN) or nystagmus elicited by visual stimulation
        • Visual stimuli need to fill at least 90% of the visual field and move in a regular & repetitive motion
        • OKN gain is measured- velocity of the nystagmus compared to velocity of the stimuli for each direction of movement
        • OKN after nystagmus- measured the velocity of nystagmus several seconds after the stimulus ceases for both clockwise and counterclockwise stimuli
        • Abnormalities can suggest involvement in the vestibulocerebellum 
      • Additional tests of ocular motility
        • Anti-saccades
        • Remembered saccades
    • VNG - Utilizes videooculography to evaluate the vestibular ocular reflex using a series of subtests to determine the presence or absence of peripheral and central vestibular lesions. Provides insight into physiologic compensation status in cases of unilateral peripheral vestibular loss.
      • Spontaneous nystagmus
        • Eye movement recordings performed with vision removed because spontaneous nystagmus will abolish with visual fixation in most cases
        • Presence of spontaneous nystagmus can be the results of a peripheral or central vestibular abnormality
        • With peripheral lesions the direction of the fast-phase of nystagmus is always toward the more excitatory ear
          • Paretic lesion will beat away from that side
          • Irritative lesion will beat toward that side
      • Post head-shake nystagmus
        • A dynamic test in which the vestibular systems are stimulated by actively moving the head and recording any post head shake nystagmus that results
        • Repetitive headshake should stimulate both horizontal semicircular canals equally with a net effect of absent nystagmus
        • Nystagmus observed post head-shake will have the direction of fast-phase toward the ear that was more stimulated
      • Positional Studies
        • Presence or absence of positional nystagmus is recorded in various positions with vision removed
          • Supine
          • Head right, left, hanging
          • Lateral right, left
          • 30-degree supine (pre-irrigation condition)
        • Presence of clinically significant positional nystagmus can be a result of peripheral or central vestibular abnormality
          • Degree and direction of nystagmus is recorded
          • Positional nystagmus in cases of unilateral peripheral vestibulopathy suggests lack of physiologic compensation
          • Purely vertical positional nystagmus most likely a result of central pathology
          • Direction changing nystagmus within a single body position is always a result of central pathology
      • Positioning Studies for BPPV
        • Can be performed as part of bedside exam with direct observation of the eyes or as part of the VNG with video eye movement recordings
        • Nystagmus cannot be suppressed with visual fixation
        • Dix-Hallpike Maneuvers
          • Evaluate for anterior or posterior canal benign paroxysmal positioning vertigo
          • Observed nystagmus is latent, torsional and fatigues 
        • Roll-test
          • Evaluate for horizontal canal benign paroxysmal positioning vertigo
          • Observed nystagmus is horizontal and can be either geotropic or ageotropic
      • Caloric Studies
        • Air or water Bithermal stimulation used to change endolymph temperature to stimulate the horizontal semicircular canal on each side individually.
        • Cool irrigation will produce nystagmus with a fast phase eye velocity that beats to the opposite side of stimulation - Warm irrigation will produce nystagmus with a fast phase eye velocity that beats to the same side of stimulation (C-O-W-S)
        • The peak slow phase of the elicited nystagmus is compared for each ear and for each direction
          • Unilateral weakness indicated when a clinically significant difference is measured for the right ear compared to the left ear
          • Directional preponderance indicated when a clinically significant difference is measured between induced right beating nystagmus (right warm, left cool irrigations) and left beating nystagmus (left warm, right cool irrigations)
          • Bilateral vestibular weakness suggested when caloric stimulation fails to produce nystagmus with a velocity that is considered normal for both ears and both stimuli temperatures
      • Rotational Chair Testing 
        • Utilizes rotational stimulation to evaluate the integrity of the vestibular ocular reflex (VOR) and provides information about physiologic compensation status in cases of unilateral peripheral vestibular hypofunction. Can provide information about residual function with bilateral peripheral vestibular weakness.
        • Uses infrared video recordings to record nystagmus induced by rotation 
        • Testing performed with vision removed so the VOR response or nystagmus cannot be suppressed with visual fixation
        • Sinusoidal Harmonic Acceleration
          • Oscillations at frequencies from 0.01-0.64 Hz
          • Measurement of gain, asymmetry and phase
        • Velocity Step Testing
          • Rotation at a constant velocity in a single direction
          • Measurement of gain and time constant for the per and post rotatory conditions for clockwise and counterclockwise stimulation
        • VEMP (vestibular evoked myogenic potentials)
          • VEMPs are vestibular assessment of the otolithic organs via air/bone conducted sound.  These stimuli do not activate semicircular canals, and are present in subjects with SNHL
          • Describe physiologic role of otolith organs
          • cVEMP: Cervical VEMP
            • Describe the reflex arc from the saccule to the sternocleidomastoid
            • Explain the technique of how cVEMP is performed
            • Analyze abnormal cVEMP findings and describe findings typically associated with inferior vestibular nerve weakness and superior semicircular canal dehiscence
            • Discuss how conductive loss and perilymphatic fistula may affect results
          • oVEMP: Ocular VEMP
            • Describe the reflex arc from the utricle to the inferior oblique muscle
            • Explain the technique of how oVEMP is performed
            • Analyze abnormal oVEMP findings and describe findings typically associated with superior vestibular nerve weakness
            • Discuss how conductive loss and perilymphatic fistula may affect results
          • vHIT (video head impulse test)
            • Describe reflex arc of horizontal VOR
            • Define ampullopetal and ampullofugal, and compare neuronal responses of these movements on the horizontal canal
            • Define refixation saccades, overt saccades, and covert saccades
            • Explain the technique of how vHIT is performed
            • Compare and contrast vHIT with beside HIT
            • Describe patient factors, such as current medical therapy and underlying medical conditions not related to dizziness, that may limit the ability to perform vHIT
            • Describe the evolution of vHIT findings from unilateral vestibular weakness to compensation
            • List abnormalities in vHIT that are consistent with a peripheral lesion
            • List abnormalities in vHIT that are consistent with a central lesion
            • Discuss applications and limitations of oblique vHIT
               
References 
  1. Jacobson, GP, Shepard, NT. Balance Function Assessment and Management. San Diego: Plural Publishing, 2008.
  2. Goebel, JA. Practical Management of the Dizzy Patient. Philadelphia: William Wilkins; 2000.
  3. Ruckenstein, MJ, Davis, S. Rapid Interpretation of Balance Function Tests. San Diego: Plural Publishing, 2015
  4. Baloh RW, Honrubia V, Kerber KA, editors.  Baloh and Honrubia’s Clinical Neurophysiology of the Vestibular System.  New York: Oxford University Press; 2011.
  5. Yang CJ, Cha EH, Park JW, et al. Diagnostic Value of Gains and Corrective Saccades in Video Head Impulse Test in Vestibular Neuritis. Otolaryngology–Head and Neck Surgery. 2018;159(2):347-353.
  6. Curthoys IS, Grant JW, Burgess AM, Pastras CJ, Brown DJ, Manzari L. Otolithic Receptor Mechanisms for Vestibular-Evoked Myogenic Potentials: A Review. Frontiers in neurology. 2018;9:366.
  7. Ostrowski VB, Bojrab DI. Chapter 14: Otolith Dysfunction and Semicircular canal Dysfunction. In Neurotology, 2e. Ed. By Jackler RK and Brackmann DE. Philadelphia: Mosby, Inc; 2005
  8. Rauch SD. Chapter 16: Vestibular Ekoved Myogenic Potentials. In Neurotology, 2e. Ed. By Jackler RK and Brackmann DE. Philadelphia: Mosby, Inc; 2005

 

Measurement of Functional Status

Learning Objectives 
  1. Describe the role of postural control studies in the comprehensive assessment of patients with vestibular and balance complaints
  • Postural Control Testing – Evaluation of functional balance ability and postural stability
    • Sensory Organization Test
      • Measurement of visual, vestibular and somatosensory inputs for maintenance of stance
      • Provides information about functional compensation status in cases of unilateral peripheral vestibular loss
    • Motor Control Test
      • Measurement of patient’s reaction time to unexpected disruptions of equilibrium
    • Adaptation Test
      • Assessment of whether patient is able to adapt to disruptions of equilibrium with repeat trials

 

References 
  1. Jacobson, GP, Shepard, NT. Balance Function Assessment and Management. San Diego: Plural Publishing, 2008.
  2. Ruckenstein, MJ, Davis, S. Rapid Interpretation of Balance Function Tests. San Diego: Plural Publishing, 2015.

 

Pathology

Learning Objectives 
  • See OTOSource modules on:
    • Sensorineural Hearing Loss
    • Ménière’s Disease
    • Benign Paroxysmal Positional Vertigo (BPPV)
    • Vestibular Migraine
    • Other Vestibular Disorders / Dizziness  

Treatment

Learning Objectives 
  • See OTOSource Vestibular Rehabilitation module

Medical Therapies

Learning Objectives 
  1. Describe effects of transtympanic gentamycin injections on vestibular testing
    • Causes unilateral vestibular loss, with predictable findings on VNG, vHIT, and rotational chair

 

References 

Nicolas S, Kmeid M, Mansour C, et al. Long-term Vertigo Control and Vestibular Function After Low-dose On-demand Transtympanic Gentamicin for Refractory Meniere's Disease. Otology & neurotology. 2019;40(2):218-225.

Pharmacology

Learning Objectives 
  • Various medications can influence vestibular testing
  • Medications with sedative effects have substantial effect of dampening response 
    • Antihistamines
    • Antiemetics
    • Anxiolytics
    • Ethanol
    • Barbituates
  • Medications with stimulant properties rarely may produce increased vestibular response
    • Nicotine
    • Amphetamines
References 
  1. Hain, TC. ( 2014, April 5). Drug Effects on Vestibular Testing. Retrieved April 9, 2019 from https://www.dizziness-and-balance.com/testing/ENG/drugs.html. 

Surgical Therapies

Learning Objectives 
  1. Otologic or neuro-otologic surgeries may alter vestibular testing results.  Often history of these procedures creates a peripheral vestibular lesion that will be identified as unilateral vestibular hypofunction.

Rehabilitation

Learning Objectives 
  1. See OTOSource Vestibular Rehabilitation module

Case Studies

Vestibular hypofunction: 38 y.o.male presents to ENT with report of a vestibular crisis described as a spontaneous attack of true spinning vertigo, nausea and emesis. The true spinning persisted for more than 3 hours regardless of position or activity. After cessation of the vertiginous symptoms he was left with daily imbalance with ambulation and non-vertiginous vague sense of dizziness and disequilibrium. This is gradually improving since the onset 2 weeks ago, but it has not resolved. MRI was negative. Complete audiologic assessment was normal. Bedside exam was normal with the exception of a positive head-
thrust to the left. Patient was referred for comprehensive vestibular work-up. VNG revealed RB nystagmus, which was observed spontaneously and in 4/6 body positions. Caloric responses yielded a 68 percent reduced vestibular response with left ear stimulation. Rotational chair testing revealed asymmetric VOR gains when rotated leftward compared to rightward with increased phase leads for low frequencies rotation. Computerized Dynamic Posturography was normal. Diagnosis = left vestibular neuritis

Questions:

  1. Is the left peripheral vestibular loss physiologically compensated for?

No – because the patient continues to have spontaneous and positional nystagmus and asymmetries on rotational chair, suggesting that physiologic compensation has not completely occurred.

  1. Is the left peripheral vestibular loss functionally compensated for?

Yes – because the patient had normal postural control when he was provided with vestibular information alone to maintain stability (normal function on conditions 5 and 6).

 

  1. Is the patient a good candidate for vestibular rehabilitation?

Yes- because he continues to have sx of imbalance with ambulation and dizziness with head/body movements he would benefit from vestibular rehab to help facilitate the compensation process.

 

BPPV: 83 y.o.female presents to her PCP with a hx of frequent falls due to unsteadiness with ambulation. She denies symptoms of dizziness with the exception of lightheadedness with orthostatic position changes. When asked to lie on the examination table she requests a pillow and reports that she is unable to lie flat and has not done so for many years. With further questioning, she reveals that she gets brief sense of motion when looking upward into high cabinets and is unable to hyperextend her neck in the beauty parlor sink because it gives her the same sense of motion. She reports that her recent falls have not resulted in injury and all of them occurred when getting out of bed in the morning. She is referred to an ENT who does a Dix-Hallpike maneuver, which results in brief nystagmus with concurrent symptoms of rapid movement. Diagnosis = right posterior canal BPPV

Questions:

  1. What features would you expect with the nystagmus elicited by the Dix-Hallpike maneuver?

The nystagmus would be torsional, slightly latent and fatigue with time or with repeat of the maneuver.

 

  1. Would this patient be a good candidate for vestibular rehabilitation? 

Yes. Not only for particle repositioning maneuvers to treat her BPPV but to do balance retraining and/or recommend assistive devices to preclude future falls.

  1. Would this patient require a comprehensive vestibular diagnostic battery?

Not necessarily. If the patient’s symptoms improve with vestibular rehab then they were likely related to BPPV and further work-up is not needed.

 

 

Complications

Learning Objectives 
  1. Describe complications of caloric testing in the presence of a perforated ear, a canal wall down mastoidectomy, or exposed encephalocele
References 
  1. Feghali JG, McElveen JT, Thedinger B, Barrs D. Chapter 56 - Complications of Ear Surgery. In: Eisele DW, Smith RV, eds. Complications in Head and Neck Surgery (Second Edition). Philadelphia: Mosby; 2009:729-738.
  2. Ahren C, Thulin CA. Lethal intracranial complications following inflation in the external auditory canal in treatment of serous otitis media due to defects in the petrous bone. Acta Otolaryngologica. 1965;60:407-421.

 

Review

Review Questions 
  1. Name 3 subtests performed during VNG:
  • Ocular motor studies
    • Gaze nystagmus
    • Random Saccade testing
    • Smooth Pursuit
    • Optokinetic Testing
  • Spontaneous nystagmus testing
  • Positional testing
  • Head-shake testing
  • Bithermal caloric testing
  1. Which test evaluates the function of the inferior vestibular nerve?
  • Cold Caloric Testing
  • Warm Caloric Testing
  • cVEMP
  • oVEMP
  1. Predict timing and course of recovery from a unilateral vestibular loss, using translabyrinthine vestibular schwannoma excision in an otherwise healthy patient as a model.  What findings do you anticipate in the first day after surgery? One week after surgery?  Six months after surgery with effective vestibular rehabilitation?

 

  1. What vestibular tests would you order first if you suspect the following pathologies or conditions?:
  • Meniere’s disease
  • Vestibular migraine
  • Confirming physiologic response to gentamycin injection
  • Malingering 
Resources 

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