Honaker, Julie A.

Adequate function of the peripheral vestibular system, specifically the vestibulo-ocular reflex (VOR; a network of neural connections between the peripheral vestibular system and the extraocular muscles) is essential for maintaining stable vision during head movements. Decreased visual acuity resulting from an impaired peripheral vestibular system may impede balance and postural control and place an individual at risk of falling. Therefore, sensitive measures of the vestibular system are warranted to screen for the tendency to fall, alerting clinicians to recommend further risk of falling assessment and referral to a falling risk reduction program. Dynamic Visual Acuity (DVA) testing is a computerized VOR assessment method to evaluate the peripheral vestibular system during head movements; reduced visual acuity as documented with DVA testing may be sensitive to screen for falling risk. This study examined the sensitivity and specificity of the computerized DVA test with yaw plane head movements for identifying community-dwelling adults (58–78 years) who are prone to falling. A total of 16 older adults with a history of two or more unexplained falls in the previous twelve months and 16 age and gender matched controls without a history of falls in the previous twelve months participated. Computerized DVA with horizontal head movements at a fixed velocity of 120 deg/sec was measured and compared with the Dynamic Gait Index (DGI) a gold standard gait assessment measurement for identifying falling risk. Receiver operating characteristics (ROC) curve analysis and area under the ROC curve (AUC) were used to assess the sensitivity and specificity of the computerized DVA as a screening measure for falling risk as determined by the DGI. Results suggested a link between computerized DVA and the propensity to fall; DVA in the yaw plane was found to be a sensitive (92%) and accurate screening measure when using a cutoff logMAR value of > 0.25.

Impairments of the vestibular-ocular reflex (VOR) lead to a decline in visual acuity during head movements. Dynamic visual acuity (DVA) testing is a sensitive assessment tool for detecting VOR impairments. DVA evaluates accuracy of visual acuity during fixed velocity head movements. In contrast, the Gaze Stabilization test (GST) is a new functional evaluation of the VOR that identifies a person's maximum head velocity (in degrees per second) a person can maintain with stable vision of a target (i.e. optotype). The objective of this study was to evaluate the effect of age on the GST in participants without vestibular disease. The study was conducted in a vestibular and balance laboratory at a tertiary medical center. A total of 87 healthy adult volunteers were included in this study. The main outcome measure was the association between age and both GST maximum head velocity in the yaw (right/left) plane and velocity symmetry. A significant negative correlation was found between age and maximum head velocity (r =−0.469, p< 0.001). Our results suggest that age should be considered when interpreting GST results in the yaw plane, however standardization of testing methods should be established as variation in results has been reported in the literature.

Objective: 1) Characterize corrective saccades (CS) in normal controls, and 2) examine the sensitivity of the video head impulse test (vHIT) for identifying vestibular loss using both gain and CS. Study Design: Prospective combined with retrospective review. Setting: Tertiary referral center. Patients: Seventy subjects with normal vestibular function served as controls (mean age, 44.1 yr; range, 10–78) and data from 49 patients with unilateral and bilateral vestibular loss was retrospectively reviewed (mean age, 50; range, 7–81). Intervention: vHIT; individual horizontal head impulses were then analyzed in MATLAB. Main Outcome Measures: Horizontal vHIT gain, CS peak velocity, frequency, and latency. Results: There was not an age effect for CS velocity or latency, and only a weak relationship between CS frequency and age in the control group. Gain and CS latency were the only parameters affected by impulse side, demonstrating higher gain and longer latency on the right. The group with vestibular loss had significantly lower mean vHIT gain, higher mean CS frequency, higher mean CS velocity, earlier CS latency, and smaller mean CS standard deviations of the latency compared with the control group. When all factors were analyzed separately by logistic regression, vHIT gain provided the best classification (83.8%), closely followed by CS frequency (83.1%). Using a two variable approach (both gain and CS frequency) yielded the best diagnostic accuracy (overall classification = 84.6%). Conclusions: Along with gain, incorporating CS frequency in interpreting vHIT improves diagnostic accuracy. A repeatable CS (>81.89%) and/or low gain (<0.78) indicate vestibular loss.

Purpose Audiologists frequently encounter patients who complain of chronic dizziness or imbalance, in the absence of active vestibular or neurological deficits. Knowledge about conditions that cause this clinical presentation will allow audiologists to make important contributions to accurate diagnosis and effective management of these patients. This article reviews 2 such conditions, chronic subjective dizziness (CSD) and conversion disorder. Method A case of CSD and another of conversion disorder are presented, with a literature review of their clinical presentations, key diagnostic features, and treatment strategies. The role of the audiologist in assessing patients with these conditions and facilitating appropriate treatment referrals is discussed. Conclusions The audiologist is in a key position to identify individuals with CSD and conversion disorder, 2 conditions that can be effectively managed if properly recognized. The authors demonstrate an effective team approach program that includes the audiologist’s contribution to differential diagnosis, education of patients and other clinicians about these conditions, and development of recommendations for neurological, psychiatric, otologic, and physical therapy referrals.

PurposeRecent research on head shake posturography has demonstrated a modest increase in sensitivity to identifying peripheral vestibular system asymmetry when horizontal head movements were added to portions of the standard Sensory Organization Test (SOT) battery. However, limitations with respect to the head shake protocol were outlined, and usable data for assessing performance could not be established. The purpose of this study was to test a change in protocol for use of head shake SOT to address the noted limitations.MethodForty participants ranging in age from 20 to 79 years with no history of dizziness completed Conditions 2 and 5 of the SOT portion of computerized dynamic posturography on EquiTest equipment, while maintaining head still as well as 4 horizontal head movement velocity tasks.ResultsSlope of a linear regression fit to 6 performance points was used to characterize each participant. Spearman’s ranked correlation (r) indicated a significant relationship between the slope of the line representing a decline in performance with age (r= −.52,p= .0006).ConclusionsThe head shake modification showed a trend in increasing the separation of normal individuals across age and eliminated the limitations addressed in earlier research. Future research will investigate the head shake modification for identifying vestibular peripheral system asymmetries.