Balance System Disorders

Assessment of a patient with dizziness and/or imbalance complaints considers both the central and peripheral vestibular system as well as sensory and motor balance components. Balance system assessment is an interdisciplinary endeavor, with audiologists serving as experts in hearing and vestibular function testing. Balance system evaluation by an audiologist may be prompted by results of a case history and/or a medical referral.

The process (whether in a screening or a comprehensive assessment) always begins with a thorough case history.

Case History

Case history information may indicate a need for modification of screening or evaluation procedures. Because the term dizziness can describe varying symptoms, and each patient may have a different idea of what dizziness means, a thorough case history is vital (Dye, 2008).

A case history specific to balance may include the following:

  • Collection of results from other health professionals
  • Fall risk data (number of previous falls, gait, mentation, reaction time, vision)
  • Medical history, including the following:
    • General health (including blood pressure and other vitals)
    • History of dizziness, balance problems, or falls
    • Medication use (prescriptions and/or over-the-counter medications)
    • Alternative medicine (e.g., homeopathy, naturopathy)
    • Presence of other co-morbidities
  • Nature of dizziness and/or imbalance symptoms, including the following:
    • Aggravating factors (motion-provoked, positional, spontaneous, diet)
    • Alleviating factors
    • Associated symptoms (e.g., auditory [hearing loss, tinnitus, aural fullness]; neurological [headache, numbness/tingling of the lips/face, diplopia, dysarthria, dysphagia, oscillopsia, photophobia, visual aura])
    • Duration (seconds, minutes, hours, days)
    • Frequency
    • Initial onset
    • Pattern (time of day, activity, symptomatic)
    • Quality and character (spinning, imbalance, disorientation)
  • Patient questionnaire on dizziness

For information regarding gathering a case history, see the Cultural Competence Practice Portal.

Screening

Performing appropriate screening measures may determine the need for further assessment, referrals, and/or a management plan when a patient reports dizziness or balance problems. Screening may assist in triaging patients, ruling out emergencies, and determining probability of central (brain/brainstem) versus peripheral (vestibular labyrinth, eighth cranial nerve) origin. Vestibular and balance screening may be performed by audiologists as well as other trained medical professionals, as appropriate.

Vestibular and Balance Screening

Screening of vestibular function and vestibular ocular reflexes (VORs) may be completed at bedside or in an office setting with little or no equipment. Normal VOR responses allow for clear vision during head and/or eye movement. Basic eye muscle function may impact eye movement tasks or vestibular function screening.

A vestibular and balance screening battery may include the following:

Observation of Nystagmus

Reflexive eye movements in response to head movement and position involve input from peripheral vestibular organs: semicircular canals (horizontal, anterior and posterior) and otolith organs (utricle and saccule). Nystagmus is a reflexive eye movement characterized by two components: the slow phase, in which the eyes drift away from center, and the fast phase, in which the eyes quickly move back toward center. Nystagmus can be observed under various conditions (normal [physiologic] and abnormal [pathophysiologic]), which are named accordingly: spontaneous, positional, evoked, congenital, and gaze.

Presence and direction of nystagmus as well as response to visual fixation may provide important information for differentiation between peripheral and central etiology of vertigo. In general, "nystagmus of peripheral origin is horizontal, and direction fixed . . . and decreases with visual fixation . . . Central signs include direction-changing nystagmus, pure vertical or torsional nystagmus and/or enhancement with fixation" (Slattery, Sinks, & Goebel, 2011, p. 145).

A screening of nystagmus may include noninstrumented tests, such as direct observation using a penlight or otoscope light. The specificity of findings will likely be reduced in comparison to those obtained with instrumented measures, such as VNG/ENG (Guidetti, Monzani, & Rovatti, 2006).

Nystagmus can be observed using both static and dynamic measures. Examples of dynamic measures are the head-shake and the head thrust (head impulse) techniques. During the head-shake assessment, the patient tilts their head down slightly and then the patient or examiner shakes the head quickly back and forth for 30 seconds (often with fixation removed), after which the eyes are examined for the presence or absence of nystagmus. Presence of head-shake nystagmus may indicate asymmetric peripheral vestibular function (e.g., semicircular canal function). The head thrust or head impulse test involves observing whether or not the patient can maintain visual fixation on a target after brief and rapid head thrusts in the planes of the semicircular canals or whether the patient requires corrective eye movements to regain eye contact with the target, which may indicate asymmetric semicircular canal function.

Dynamic Visual Acuity Test

The dynamic visual acuity test assesses the VOR by having the patient read a Snellen eye chart first in a static position and then while the head is rotated back and forth. The lowest line on the eye chart where 50% of the characters are correctly identified may be used to compare static versus dynamic visual acuity results. The possibility of VOR deficit depends on how many lines are lost in this comparison. The difference between static and dynamic visual acuity may indicate peripheral vestibular loss as related to gaze stabilization. Computerized systems are also available for the measurement of dynamic visual acuity.

Eye Movement Tests

Voluntary and reflexive eye movements can include saccadic tracking (shift in gaze from one point to another) and smooth pursuit (following a slowly moving target across the visual field). If a patient shows significant abnormalities in these functions, they may require a referral to neurology or neuro-ophthalmology for assessment of central nervous system function.

Dix-Hallpike Maneuver

This specific positioning maneuver is often used to observe nystagmus and/or vertigo associated with BPPV. The patient is moved somewhat briskly from sitting to supine position with their head hanging below their shoulders and turned 30-45º to the left or right (Dix & Hallpike, 1952). After the maneuver, the examiner observes whether nystagmus is present and, if so, notes the duration and direction of nystagmus. They also consider whether nystagmus intensity is reduced with repeated maneuvers. Abnormal results may indicate the need for canalith repositioning procedures.

Screening For Differentiation of Acute Stroke

One screening objective is to differentiate between peripheral causes (e.g., vestibular neuritis) and central causes (e.g., acute cerebellar stroke) when a patient presents with acute vestibular syndrome (AVS)—a term used to describe the presence of "severe vertigo, nausea and vomiting, spontaneous nystagmus, and postural instability" (Hotson & Baloh, 1998, p. 680). One review of the literature (1966-1996) determined that etiologies for dizziness included 35%-55% peripheral vestibulopathies, 10%-25% psychiatric disorders, 5% cerebrovascular disease, and less than 1% brain tumor, while also noting that the symptom of dizziness can be multifactorial (Hoffman, Einstadter, & Kroenke, 1999).

HINTS is a three-step oculomotor/VOR test protocol that includes (a) the Head-Impulse test, (b) interpretation of Nystagmus, and (c) Test-of-Skew (Kattah, Talkad, Wang, Hsieh, & Newman-Toker, 2009). Skew deviation is a vertical misalignment of the eyes that can be tested by covering the patient's eyes, one at a time, while he or she focuses on a fixed target.

Screening Considerations

When screening for dizziness and/or imbalance, the following considerations are important:

  • Screening measures may be accompanied by postural or gait observations.
  • To rule out orthostatic hypotension, you can measure the patient's blood pressure after they have been lying down for several minutes (measurement occurs while they are still supine) and then again after they quickly stand up.
  • Some assessment techniques for vestibular function that require equipment or instrumentation may also be considered bedside-appropriate if the clinician has access to the technology (e.g., Frenzel glasses, VNG, vHIT, VEMP).
  • Sensitivity and specificity of bedside vestibular screening measures will vary (Cohen, Sangi-Haghpeykar, Ricci, Kampangkaew, & Williamson, 2014; Herdman et al., 1998; Jacobson, Newman, & Safadi, 1990; Zamyslowska-Szmytke, Szostek-Rogula, & Sliwinska-Kowalska, 2015; Kattah et al., 2009), whether taken individually or collectively.
  • Screening tests in combination may provide more specific results; however, interpretation of findings by the examiner requires in-depth knowledge and understanding.

Comprehensive Assessment

Accurate differential diagnosis of balance system disorders relies partly on the audiologist's interpretation of a test battery within the context of the individual's medical history. Comprehensive assessment of dizziness and/or balance complaints will include a case history (as outlined above), results from any number of screening tests (described above), as well as an audiologic assessment, in-depth vestibular assessments (described below), and information from outside referrals or sources (as part of an interdisciplinary team).

Audiometry

Comprehensive assessment of a patient with dizziness, vertigo, or imbalance may include audiometric assessment. There is a close relationship between hearing and balance in relation to inner ear organs. Some patients with dizziness and imbalance symptoms will have co-existing auditory symptoms. For example, the combination of vertigo and audiologic symptoms is a classic presentation in a patient with labyrinthitis and may also be seen in patients after they experience head trauma. Audiologic assessment can provide information about possible retrocochlear or middle ear pathologies that may need to be addressed prior to further vestibular testing and follow-up.

Audiometric assessment in a patient with dizziness, vertigo, or imbalance complaints may include

  • auditory brainstem response (ABR),
  • electrocochleography (ECOG),
  • immitance testing,
  • otoacoustic emissions (OAE),
  • otoscopy,
  • pure-tone testing, and
  • speech audiometry.

See Hearing Loss: Beyond Early Childhood: Assessment and Joint Audiology Committee Clinical Practice Statements and Algorithms for detailed information on audiologic assessment.

Balance System Testing

Balance system testing may include a combination of tests. Results and combinations of results from vestibular tests require complex interpretation and can indicate various deficits. The audiologist strives for differential diagnosis and differentiation of unilateral versus bilateral vestibular disorders.

In interprofessional practice (IPP) settings, vital signs such as blood pressure and oxygen saturation may be measured prior to patients receiving a full balance assessment (Dye, 2008). These measurements are important as symptoms of dizziness stem from a variety of etiologies that may be multifactorial.

VNG (Videonystagmography)/ENG (Electronystagmography)

Videonystagmography (VNG) and electronystagmography (ENG) are techniques used to measure and record a patient's eye movements, including nystagmus, during a variety of tasks and conditions. Both VNG and ENG include computer analysis of eye movements. ENG is a process of recording eye movement indirectly through the electrical potential difference between the front and back of the eye. Electrodes are placed around the eyes during ENG. VNG has become a standard in balance assessment and uses infrared video technology to record eye movement while the patient's eyes are open in darkness. Completing testing in dark minimizes the possibility that nystagmus will be suppressed by visual fixation. VNG/ENG technology may be used when conducting oculomotor tests, positional and positioning tests, and/or caloric tests.

Oculomotor assessments of gaze nystagmus and spontaneous nystagmus are enhanced with the use of VNG/ENG, which allows for measurement of nystagmus intensity and direction. Measurements of intensity and direction may be taken without fixation (i.e., in complete darkness). It is important to consider these measurements because some level of spontaneous nystagmus may be seen in healthy individuals (Levo, Aalto, & Petteri Hirvonen, 2004). VNG/ENG technology allows for evaluation of eye control with oculomotor tests, including saccades, smooth pursuit, and optokinetic nystagmus:

  • Saccades are voluntary and reflexive rapid eye movements of varying amplitude that abruptly change a point of fixation and may be used to bring a target object into the center line of sight.
  • Smooth pursuit refers to tracking eye movements that enable stable gaze to be sustained on a moving object or on a stationary target when the head is moving slowly.
  • Optokinetic nystagmus or optokinetic tracking refers to a normal reflexive response of the eyes when confronted with large-scale movement in the visual field.

Static and dynamic position tests are used to observe the vestibular system response to a change in head/body position as compared with neutral head/body position. The measurements are taken with or without fixation. The examiner considers the presence or absence of nystagmus and/or changes in nystagmus as well as the patient's subjective report of symptom changes.

Positional tests are most often used to elicit signs and symptoms of BPPV and to aid in diagnosing this disorder. The Dix-Hallpike maneuver is one positional test that can be used, depending on characteristics of the patient and determination of risk factors. Symptoms of BPPV occur when otoconia moves into one of the semicircular canals. Movement of a patient from one position to another elicits or exacerbates these symptoms.

Caloric tests stimulate the vestibular system in the ear by creating a temperature difference relative to body temperature. Methods used to create a temperature change include heated or cooled air introduced to the ear canal, heated or cooled water introduced directly into the ear canal (open-loop), and heated or cooled water introduced into the ear canal inside of a balloon (closed-loop). Only a few closed-loop systems are still used in clinical practice. Testing typically includes presenting either cool and warm air or water into each ear canal in succession. The examiner looks for the presence, strength, and direction of any nystagmus that exists during and following the introduction of each stimulus. This technique allows the examiner to evaluate each labyrinth independently by comparing the strength of nystagmus that results from stimulating both the left and right sides. Fitzgerald and Hallpike (1942) provided a description of one widely used caloric technique.

Considerations with caloric testing include the following:

  • Responses to cool and warm stimulus introduction will differ: Warm irrigations produce an excitatory response that causes the fast phase of nystagmus to beat toward the stimulated ear; cool irrigations produce an inhibitory response that causes the fast phase of nystagmus to beat away from the stimulated ear.
  • Providing appropriate alerting tasks to distract the patient during caloric testing is important so that the resulting nystagmus is not affected by central suppression. Formby et al. (1992) provided a comparison and ranking of several different alerting tasks used during observation of caloric-induced nystagmus.
  • When standard procedures for caloric testing do not elicit a response in a given individual, ice water caloric testing may be introduced (or the examiner may choose to move on to rotary chair testing).
  • Visual fixation can be assessed following the response to caloric stimulation and should reduce the intensity of nystagmus. Failure of fixation suppression may indicate a central deficit.
  • Some patients will not be able to tolerate caloric testing.
  • Open-loop water irrigation is contraindicated if the patient has a perforated tympanic membrane or has pressure-equalizing tubes in place.
  • Caloric testing should not be performed on any patient with cerumen obstruction of either/both ear canal(s).
  • Caution should be used when performing and/or interpreting caloric responses on patients with history of ear surgery in which anatomy of the temporal bone has been altered (e.g., mastoidectomy).

Other tests that can be included in a VNG/ENG battery are hyperventilation testing, vibration testing, and head-shake testing (previously described).

  • Hyperventilation testing requires the patient to take deep, rapid breaths for 30-60 seconds. The examiner observes any nystagmus during this state of hyperventilation and then observes any changes in the presence or intensity of nystagmus after hyperventilation concludes.
  • Vibration testing involves placing a handheld vibrating instrument on the left and right mastoid bone and on the left and right posterior sternocleidomastoid muscle (SCM) and then observing changes in the presence or intensity of nystagmus. The results may be abnormal in patients with superior semicircular canal dehiscence or unilateral vestibular hypofunction.
  • Head-shake testing as described above.
Rotary Chair Testing

Rotary chair testing can be helpful in detecting bilateral and uncompensated unilateral vestibular disorders. Results may be more accurate when used in conjunction with VNG/ENG. Testing involves whole body rotation with the patient seated and restrained in a motorized rotary chair. Eye movements are recorded in darkness using electrodes, as in ENG, or while the patient is wearing video-oculography goggles, as in VNG. The patient's head is properly secured so that the chair and head movements correspond. It is important to record baseline spontaneous nystagmus and gaze nystagmus prior to rotary chair testing. A rotary chair test battery may include sinusoidal harmonic acceleration tests, visual-vestibular interaction tests (i.e., visual-vestibular ocular reflex and visual-vestibular fixation), and step velocity tests, as follows:

  • Sinusoidal harmonic acceleration testing involves rotating/oscillating the patient in alternating directions, rightward (clockwise) and leftward (counterclockwise), at varying harmonic frequencies. Measurements of gain (eye movement in relation to head movement), phase (timing relationship between eye movement and head movement), and symmetry (nystagmus from rightward versus leftward rotations) are derived from the eye movement recordings.
  • Visual-vestibular interaction tests assess whether the addition of visual cues results in changes of VOR gain.
    • Visual-vestibular ocular reflex testing involves the patient viewing objects on the wall as the chair turns rightward and leftward; this typically results in an increase in VOR gain compared with VOR gain measured in darkness.
    • Visual-vestibular fixation or suppression testing involves the patient fixating on a visual target that moves along with the rotary chair; this typically results in a decrease in VOR gain compared with VOR gain measured in darkness.
  • Step velocity testing involves (a) rapid acceleration of the chair in one direction, (b) rotation at a constant speed for about 1 minute, (c) abrupt deceleration of the chair. The examiner measures the time it takes for the nystagmus to decay in each direction of rotation or the peak nystagmus response.

Rotary chair testing assesses both ears simultaneously, rather than independently. A natural stimulus allows for VOR measurements to be taken during physiologically relevant stimulation (i.e., head rotation) at a variety of frequencies. Rotational testing provides important information about residual vestibular function in individuals with bilateral vestibular weakness on caloric testing. This information is critical in selecting appropriate rehabilitative strategies.

Computerized Dynamic Posturography (CDP)

Computerized dynamic posturography is a method of assessing an individual's functional balance and the contribution of visual, vestibular, and somatosensory inputs. CDP does not provide information regarding possible location of lesion or possible etiology of balance disorders. Equipment required for CDP includes a movable support surface (a force platform) within a movable enclosure.

Subtests include the following:

  • The Sensory Organization Test (SOT) involves measuring an individual's postural stability or sway under varied circumstances, such as stable support surface versus moving support surface and with eyes open versus with eyes closed. Based on postural control performance in each circumstance, a pattern is generated, which can be associated with functional impairments. Reduced performance scores on the SOT have been documented in individuals with a history of multiple falls as compared with individuals with a history of 0 or 1 falls (Whitney, Marchetti, & Schade, 2006).
  • The Motor Control Test (MCT) involves disturbing the individual's postural control with unexpected linear movements of the support surface and then observing and measuring their response to and recovery from these disturbances. This measure of sensory input and motor output is important in interpreting the SOT as well as predicting future falls.
  • The Adaptation Test (ADT) involves unpredictable movement of the support surface in either the toes-up or toes-down position, which is meant to simulate irregular walking surfaces. The individual's ability to reduce sway and overcome instability is assessed.
Vestibular Evoked Myogenic Potentials (VEMP)

Vestibular evoked myogenic potentials (VEMP) offer an electrophysiological method of testing otolith (saccule and utricle) function and potentially both branches of the vestibular nerve. VEMP testing involves measuring a motor response to sound stimulation of the otolith organs.

There are two types of VEMP testing. The cervical VEMP (cVEMP) measures a relaxation response in the SCM coincident with presentation of sound or vibration. Electrodes are placed in a specified configuration on the SCM and on the forehead. Because the cVEMP is a relaxation response, the SCM must be activated (contracted) either unilaterally or bilaterally through intentional head positioning by the patient. The ocular VEMP (oVEMP) uses electrode placement under the eyes and on the forehead and measures an activation response from those muscles. For both types of VEMP testing, clicks and/or tone bursts are introduced via earphones or a bone conduction oscillator. Recordings of waveforms are taken, and asymmetries can be identified between responses generated by stimulating the right and left ears.

Results of VEMP testing may provide insight into pathologies that affect balance and/or cause dizziness, such as superior semicircular canal dehiscence and vestibular neuritis. The use of one of these tests as opposed to the other (oVEMP, cVEMP) may be preferred for certain patients and/or situations. As with any vestibular test, VEMP results must be interpreted by a knowledgeable clinician and in the context of the patient's personal history and characteristics. For example, patient age may impact VEMP results (Janky & Shepard, 2009; Ochi & Ohashi, 2003).

In addition to VEMP testing, other tests are available to measure otolith function. The subjective visual vertical (SVV) test is one in which a patient is asked to adjust an illuminated straight line against a featureless background until it appears to be completely vertical to them. Abnormalities in the SVV may reflect the presence of vestibular (otolith) dysfunction.

Video Head Impulse Test (vHIT)

The video head impulse test (vHIT) is an instrumented version of the Head Impulse Test (HIT) using infrared video recording of eye movements in response to short, brisk head turns or impulses in the plane of the semicircular canal. This allows for objective measurement of eye movements rather than subjective clinician observations. The patient is instructed to maintain visual contact on a stationary target during head impulses. Eye movements are analyzed to determine whether the eyes (a) moved in the same direction as the head during impulses and then made a corrective refixation back to the target (abnormal) or (b) moved in the opposite direction of the head during impulses and maintained fixation on the target (normal). Results may demonstrate a problem with semicircular canal function on the same side to which the head was turned prior to the corrective refixation response. This procedure is noninvasive, relatively short, and utilizes stimuli in the physiological range of everyday head movement.

Outside Referrals/Interprofessional Practice (IPP)

Interprofessional practice (IPP) occurs when two or more professions collaborate with each other to improve health outcomes for a patient. This approach is vital in assessment and management of balance and vestibular disorders. In addition to tests and services offered by a trained audiologist, the patient may require input from other medical professionals both to complete a comprehensive evaluation and to conduct management planning. For example, the patient may require medical imaging studies (CT/MRI), a gait assessment by a vestibular physical therapist, or a review of medications by their primary care physician. See Interprofessional Education/Interprofessional Practice (IPE/IPP) and Interprofessional Education/Interprofessional Practice (IPE/IPP) Resources for more information on this topic.

Assessment Considerations

Pediatrics

Depending on the age, compliance, and understanding of the pediatric patient, it may not be possible to obtain a complete balance function examination. However, as with pediatric hearing assessment, experts in assessment of pediatric dizziness have the skills necessary to adjust testing methods to collect useful information regarding the status of a child's vestibular function and overall balance.

Equipment and Test Environment

It is essential that all audiometric equipment be calibrated, be functioning properly, and be used in an acceptable test environment free of electrical interference to ensure accurate test results as specified in American National Standards Institute (ANSI) Standard s3.6-2010 (ANSI, 2010).

Infection Control

Adherence to universal precautions should be followed, and appropriate infection control procedures should be in place. Instrumentation coming into physical contact with the patient must be cleaned and disinfected after each use. Disposable acoustically transparent earphone covers or disposable insert earphone tips are recommended, and hand washing between patients should be routine (Siegel, Rhinehart, Jackson, Chiarello, & the Healthcare Infection Control Practices Advisory Committee, 2007). See the Occupational Safety and Health Administration (OSHA) standards relating to occupational exposure to bloodborne pathogens, and the Center for Disease Control and Prevention's universal precautions for preventing transmission of bloodborne infections.

Outcomes/Recommendations

Interpretation and integration of comprehensive balance assessment results may indicate normal versus abnormal balance system function. Abnormal results may indicate reason or origin, such as unilateral or bilateral peripheral vestibular hypofunction or central vestibular origin (e.g., incomplete central compensation or abnormal visual-vestibular interaction). Finally, an idea of how dizziness and/or disequilibrium functionally impacts the patient may be obtained with dizziness scales or questionnaires.

Recommendations from the audiologist may include referral to other professionals, referral to a vestibular/balance rehabilitation program, routine follow-up, and/or discharge from audiologic services.

Content Disclaimer: The Practice Portal, ASHA policy documents, and guidelines contain information for use in all settings; however, members must consider all applicable local, state and federal requirements when applying the information in their specific work setting.