Susan J. Herdman

Computerized dynamic visual acuity test in the assessment of vestibular deficits.

OBJECTIVE The study was designed to measure dynamic visual acuity (DVA) during head movement as an assessment of the functional impact of vestibular deficits. STUDY DESIGN The study design was a prospective, clinical study. SETTING The study was performed in a tertiary, ambulatory referral center. PATIENTS Forty-two normal subjects, 29 patients with unilateral vestibular loss, and 26 patients with bilateral vestibular hypofunction who were 19-87 years of age were examined. INTERVENTION Diagnostic intervention was performed. MAIN OUTCOME MEASURE Main outcome measures included the reliability, sensitivity, and specificity of a computerized test that measures visual acuity during head movement in normal subjects and in patients with vestibular deficits. RESULTS The computerized DVA test was reliable in both normal subjects (intraclass correlation coefficient [ICC] r=0.87) and in patients with vestibular deficits (ICC r=0.83). The sensitivity of the DVA test was 94.5% and the specificity was 95.2%. The positive predictive value (individuals who test positive on the DVA test who will have a vestibular deficit) was 96.3%. The negative predictive value (individuals who test negative on the DVA test who will not have a vestibular deficit) was 93%. CONCLUSIONS The computerized DVA test is reliable and is able to distinguish among normal subjects and patients with vestibular deficits.

Preclinical Disability: Hypotheses About the Bottom of the Iceberg

Accomplishing a compression of morbidity will require prevention of disability, a significant component of illness in older adults. To do this, better understanding is needed of the natural history of functional loss prior to disability. The authors hypothesize that there is an identifiable stage of preclinical disability that will predict future disability and identify a focus for prevention. It is proposed, based on observations in the Johns Hopkins Functional Status Laboratory, that preclinical disability is characterized by persons who perceive no difficulty with performance of a task and yet are found to have either (a) general diminution in activities requiring related abilities, or (b) changes in the performance of specific tasks. Both models are due to impairments. The authors suggest that nondisabled persons use compensatory strategies that minimize functional restrictions resulting from impairment; this may keep functional decline at a preclinical level. These hypotheses, if verified in prospective studies, may provide a basis for early detection of those at risk of disability and suggest effective preventive measures.

Vestibular Adaptation Exercises and Recovery: Acute Stage after Acoustic Neuroma Resection

The use of exercises in the treatment of patients with vestibular deficits has become increasingly popular, and evidence exists that these exercises are beneficial in patients with chronic vestibular deficits. The question as to whether patients with acute unilateral vestibular loss would benefit from vestibular adaptation exercises is particularly compelling, however, because animal studies have demonstrated that the acute stage after unilateral vestibular loss is a critical period for recovery. Deprivation of visuomotor experience during that period can delay the onset of recovery as well as prolong the recovery period. Patients often avoid movement during the early stage because, with movement, they experience an increase in dysequilibrium and nausea. We examined the recovery of postural stability in patients during the acute stage after resection of acoustic neuroma to determine whether vestibular adaptation exercises facilitate the onset of recovery and improve the rate of recovery. The results suggest that vestibular adaptation exercises result in improved postural stability and in a diminished perception of dysequilibrium.

Role of vestibular adaptation in vestibular rehabilitation

Recovery of gaze and postural stability in human beings with vestibular deficits is well documented. The mechanisms that contribute to this recovery form the basis for the exercises used in the rehabilitation of these patients. These mechanisms include the central preprogramming of eye movements and of postural responses, the potentiation of the cervico-ocular reflex, modification of saccadic eye movements, and the substitution of visual and somatosensory cues for the lost vestibular cues. The mechanism most successful in contributing to recovery, however, is probably adaptation of the vestibular system itself. Understanding the various compensatory mechanisms and their limitations for improving gaze and postural stability should lead to more effective treatment of these patients. (Otolaryngol Head Neck Surg 1998;119:49–54.)

Virtual reality rehabilitation of balance: assessment of the usability of the Nintendo Wii® Fit Plus

Purpose: The aim of this study was to investigate the usability of the Nintendo Wii Fit Plus® (NWFP) in the treatment of balance impairment in vestibular and other neurological disease. Methods: This was a cross-sectional, quasi-experimental study. Participants (n = 26; mean age 43 ± 14, M13:F13) with quantified balance impairment took part in a 30-minute session on the NWFP using exercises and games that challenge balance. Outcomes included the System Usability Scale (SUS), a numerical rating scale of enjoyment and a post treatment questionnaire. Results: The mean SUS score was high (mean 82 ± 18%) with only two participants rating below 50%. There was a negative correlation of age with SUS scores (r = −0.54; p = 0.004). Mean numerical rating scale score (/10) for enjoyment of the NWFP session was 8.4 ± 3. Of the participants, 88.5% said that they would like to use the NWFP in future treatment. Seventy-three percent reported more enjoyment and motivation than usual physiotherapy. No falls occurred during testing. Conclusions: This study has quantified the usability of the NWFP as a treatment for balance impairment showing high levels of usability and enjoyment with no serious adverse effects. The results of this study may assist physiotherapists in devising novel balance rehabilitation programmes. Implications for Rehabilitation The Nintendo Wii Fit Plus® virtual reality system has the potential to improve balance rehabilitation, but usability of this system requires investigation. In this study, patients with balance impairment as a result of neurological disease reported very high levels of usability and enjoyment when performing selected Nintendo Wii Fit Plus® balance exercises and games. The majority of patients preferred the Nintendo Wii Fit Plus to conventional treatment which may have implications for patient compliance with exercise.

Prediction of Fall Risk Reduction as Measured by Dynamic Gait Index in Individuals with Unilateral Vestibular Hypofunction

Objective: To determine the effect of vestibular rehabilitation on reduction of fall risk in individuals with unilateral vestibular hypofunction and to identify those factors that predict fall risk reduction. Study Design: Retrospective chart review. Setting: Tertiary referral center. Patients: Forty-seven patients with unilateral vestibular hypofunction, aged 28 to 86 years, who were at risk for falls on initial assessment. Intervention: All patients underwent vestibular rehabilitation including adaptation exercises, designed to improve gaze stability, and gait and balance exercises. Main Outcome Measures: Fall risk (Dynamic Gait Index), visual acuity during head movements (Dynamic Visual Acuity), and subjective complaints were measured initially, at 2-week intervals, and at completion of physical therapy. Results: As a group, the patients had significantly reduced risk for falls (p < 0.001) after rehabilitation. Time from onset of symptoms did not affect the efficacy of vestibular rehabilitation. Both older (≥ 65 yr) and younger (< 65 yr) adults showed significant reductions in fall risk with vestibular rehabilitation (p < 0.001). However, a significantly greater proportion (χ2 = 0.016) of older adults remained at risk for falls at discharge compared with young adults (45% versus 11%). Initial Dynamic Gait Index and Dynamic Visual Acuity scores predicted fall risk reduction in patients with unilateral vestibular hypofunction. A model was developed using initial Dynamic Gait Index and Dynamic Visual Acuity scores to predict fall risk reduction. Conclusions: Vestibular rehabilitation is effective in significantly reducing fall risk in individuals with unilateral vestibular deficit. The model predicts fall risk reduction with good sensitivity (77%) and specificity (90%).

Vertical dynamic visual acuity in normal subjects and patients with vestibular hypofunction.

Objective This study was designed to measure visual acuity during active vertical head movement and to examine its relationship to subjective reports of oscillopsia. Study Design This was a prospective, clinical study. Setting The study was performed in a tertiary, ambulatory referral center. Patients Thirty normal subjects, 13 patients with unilateral vestibular hypofunction, 11 patients with bilateral vestibular loss, and 10 patients with nonvestibular dizziness were examined. Vestibular loss was confirmed with caloric or rotary chair testing. Intervention Diagnostic. Main Outcome Measure Reliability, sensitivity, and specificity of a computerized test that measures visual acuity during active vertical head movement. Subjective complaint of oscillopsia was measured by use of a visual analog scale. Results The active vertical head movement test was reliable both for normal subjects (intraclass correlation coefficient, r = 0.89) and for patients with dizziness (intraclass correlation coefficient, r = 0.94). Age contributed significantly to active vertical head movement in normal subjects and in patients with dizziness over the age of 46 years but not in younger subjects. Older subjects had a decrement in active vertical head movement compared with younger subjects. Subjective reports of oscillopsia did not correlate positively with active vertical head movement. Conclusion The active vertical head movement test is a reliable measure of visual acuity during active vertical head motion. The effect of age on active vertical head movement may reflect the physiologic impact of neuronal loss with aging. The poor correlation between active vertical head movement and reports of oscillopsia may be caused by the predictability of head movements during the active vertical head movement test compared with the unpredictability of head movements during walking.

Postural stability in patients with Huntington's disease

We characterized postural stability in patients with Huntingtons disease (HD) by examining their ability to use different sensory cues to maintain balance and by recording their automatic postural responses to externally applied perturbations. Our HD patients, like normal subjects, depended more on proprioceptive than on visual cues to maintain balance. HD patients, however, developed more sway than normal subjects when proprioceptive cues, or when proprioceptive cues and vision, were altered. Thus, HD patients showed a defect in using vestibular information alone to maintain normal postural stability. The onset of compensatory motor responses in the lower extremities following sudden translations of the support surface was delayed by 30 to 60 msec in HD patients as compared with normal subjects. HD patients also had more sway and falls during unexpected rotations of the support surface, although they could appropriately reduce their motor responses on the next trial.

Strategies for balance rehabilitation: fall risk and treatment.

Abstract: Identification of fall risk for patients with known vestibular hypofunction is important because it affects the management and the level of independence of these patients. Patients with bilateral vestibular loss, overall, have a greater incidence of falls than the general community‐dwelling population over the age of 65 years. In younger patients, the incidence of falls may be related to severity of vestibular loss and to overconfidence or a lack of caution in activities. Preliminary reports suggest that vestibular rehabilitation can reduce the fall risk in patients with vestibular loss.

Reliability of clinical measures used to assess patients with peripheral vestibular disorders.

Purpose The purposes of this research were to (1) determine test-retest reliability of clinical measures of self reported disability and subjective complaints, gait, and fall risk; and (2) establish normal variability for each of these measures based on test-retest variability in people with peripheral vestibular disorders. Methods Sixteen patients with confirmed peripheral vestibular disorders performed 2 trials of each of the measures within a single physical therapy session. The measures included rating of disability, percent of day affected by dizziness, head movement induced dizziness, preferred gait speed, gait deviations, and Dynamic Gait Index. In order to assess test-retest reliability of the measures intraclass correlation coefficients (ICC) were calculated. Results All measurement tools demonstrated excellent reliability (ICC 3,1 = 0.86–1.00) except for head movement induced dizziness (ICC 3,1 = 0.48). For each measure we report normal variability as tested within a single session. Discussion Clinical measures commonly used in the assessment of vestibular patients were found to have excellent test-retest reliability, except for the subjective measure of head movement-induced dizziness. Conclusion Incorporation of valid and reliable assessments in clinical practice is critical in order to demonstrate the effectiveness of therapeutic intervention.