Visual dependency and dizziness after vestibular neuritis

Abstract

Symptomatic recovery after acute vestibular neuritis (VN) is variable, with around 50% of patients reporting long term vestibular symptoms; hence, it is essential to identify factors related to poor clinical outcome. Here we investigated whether excessive reliance on visual input for spatial orientation (visual dependence) was associated with long term vestibular symptoms following acute VN. Twenty-eight patients with VN and 25 normal control subjects were included. Patients were enrolled at least 6 months after acute illness. Recovery status was not a criterion for study entry, allowing recruitment of patients with a full range of persistent symptoms. We measured visual dependence with a laptop-based Rod-and-Disk Test and severity of symptoms with the Dizziness Handicap Inventory (DHI). The third of patients showing the worst clinical outcomes (mean DHI score 36-80) had significantly greater visual dependence than normal subjects (6.35° error vs. 3.39° respectively, p = 0.03). Asymptomatic patients and those with minor residual symptoms did not differ from controls. Visual dependence was associated with high levels of persistent vestibular symptoms after acute VN. Over-reliance on visual information for spatial orientation is one characteristic of poorly recovered vestibular neuritis patients. The finding may be clinically useful given that visual dependence may be modified through rehabilitation desensitization techniques.

Figure 1. Experimental set up and rod tilt in normals and high DHI patient group. A.

Rod and Disk test experimental set up. Laptop-based Rod-and-Disk test to measure visual dependency, showing a subject viewing the screen through a field-restricting cone. Subjects carried out the test in a darkened room. B. Rod tilt in normals and high DHI patient group. Figure showing similar mean rod tilt (deg; ± SE) in the static condition for the normal control and high DHI patient groups. Also shown is visually induced rod tilt for both normal and High DHI groups, which is higher in the unrecovered patient group, despite similar values in the static condition.

Figure 2. Visually induced rod tilt for all patient groups and normals.

Figure showing visually induced rod tilt (mean, ±SE) for all patient groups (High DHI; Low DHI; Asymptomatic). Shaded grey area represents 95% confidence interval of the mean for normal controls. Note, rod tilt values for Low DHI and Asymptomatic patient groups are within normal range, where as High DHI patients show significantly higher than normal rod tilts in the moving disk condition.