Association of the Video Head Impulse Test With Improvement of Dynamic Balance and Fall Risk in Patients With Dizziness

Abstract

Importance: It is important to know whether recovery of the vestibuloocular reflex (VOR) as measured by the video head impulse test (vHIT) is associated with the recovery of dynamic balance. It is also critical to know how much change in VOR gain is clinically relevant for establishing the recovery of dynamic balance.

Objectives: To investigate the association between improved VOR gain as measured by the vHIT and improved dynamic balance (reduced fall risk) as measured by the dynamic gait index (DGI) and to calculate the minimal clinically important difference of VOR gain.

Design, setting, and participants: This retrospective case series study was performed at a tertiary referral center at the Johns Hopkins University School of Medicine. Thirty-eight consecutive patients with subacute or chronic dizziness from January 1, 2014, through May 31, 2017, who visited the vestibular physical therapy clinic were included in the study.

Interventions: Each patient was evaluated with room light and video-infrared oculomotor examination, vHIT, and balance testing before and after vestibular physical therapy.

Main outcomes and measures: Gain of the lesioned VOR and score on the DGI.

Results: Among the 38 patients (25 women [66%]; mean [SD] age, 65 [14] years), the mean (SD) initial lesioned VOR gain was 0.66 (0.23) and initial DGI score was 16 (3). No correlation was found between initial VOR gain and initial DGI score (r = -0.04; 95% CI, -0.35 to 0.28). At follow-up, 15 patients (39%) had an improved VOR gain and 30 (79%) had an improved DGI score, which was correlated (r = 0.49; 95% CI, 0.20-0.69). In those 15 patients with improved VOR gain, 14 (93%) had improvement of DGI score. In the 23 patients without improvement of VOR gain, 16 (70%) still showed improvement in their DGI score. When using VOR gain to estimate improvement of DGI, the minimal clinically important difference of VOR gain was -0.06.

Conclusions and relevance: The change of VOR gain in the vHIT was moderately associated with the change of DGI score. Improved VOR gain was associated with a high probability of improved dynamic balance. However, in most of the patients whose VOR gains did not improve, balance improvement occurred putatively through sensory reweighting strategies.

Figure 1.. Correlation Analysis Between Vestibuloocular Reflex (VOR) Gain and Dynamic Gait Index (DGI)

A, No significant correlation occurred between initial VOR gain and initial DGI score. B, During follow-up, there was a moderate correlation between the improvement of VOR gain and the improvement of DGI score, with improvement measured as the difference between measurements after and before vestibular physical therapy. Circles indicate individual data points; horizontal line, linear regression.

Figure 2.. Intragroup Correlation Analysis

Data are presented as the correlation between the improvement in lesioned vestibuloocular reflex (VOR) gain and the improvement in the dynamic gait index (DGI) score, with improvement measured as the difference between measurements after and before vestibular physical therapy (ΔVOR and ΔDGI). Patients are stratified by diagnosis of unilateral vestibular hypofunction (UVH) (n = 18), bilateral vestibular hypofunction (BVH) (n = 11), and other dizziness (n = 9). A, ∆VOR was moderately correlated with ∆DGI in the UVH group. B, ∆VOR was highly correlated with ∆DGI in the BVH group. C, ∆VOR was not significantly correlated with ∆DGI in the other dizziness group. Circles indicate individual data points; horizontal line, linear regression.

Figure 3.. Receiver Operating Characteristic (ROC) Analysis for Detecting Improvement and Significant Improvement of Dynamic Gait Index (DGI) by Vestibuloocular Reflex (VOR) Gain

Improvement of DGI indicates a difference (ΔDGI) of at least 1; significant improvement, a ΔDGI of at least 4. Solid line indicates ROC curve; broken line, reference line. A, When improvement of DGI indicates a significant difference (ΔDGI) of at least 1, the area under ROC curve (AUC) is 0.83. The optimum cutoff point is −0.06 with sensitivity of 86.7% (95% CI, 70.3%-94.7%) and specificity of 75% (95% CI, 40.9%-92.9%). B, When the ΔDGI indicates a significant difference of at least 4, the AUC is 0.74 and the optimum cutoff point is −0.02 with sensitivity of 100% (95% CI, 64.6%-100%) and specificity of 51.6% (95% CI, 34.8%-68.0%). Solid line indicates ROC curve; broken line denotes reference line.