OBJECTIVE Gait imbalance in patients with bilateral-vestibular-deficiency (BVD) was linked to increased variability in perceived direction of gravity while upright. We hypothesized this to be true also when roll-tilted. Moreover, as utricular input is essential for spatial orientation, we predicted the variability of perceived vertical to correlate inversely with utricular function.
METHODS Subjective visual vertical (SVV) and haptic vertical (SHV) were measured in various roll-orientations (0°/±45°/±90°) and postural adjustments along earth-vertical/earth-horizontal were collected in patients with partial BVD (n = 10) and healthy controls (n = 11). Patients with bilaterally-absent bone-conducted ocular vestibular-evoked myogenic-potentials (oVEMPs) were compared to those with (partially) preserved oVEMPs.
RESULTS For the SVV (p < 0.001) and SHV (p = 0.004) variability was larger in patients than controls. Compared to those with (partially) preserved oVEMPs, patients with bilaterally-absent oVEMPs had higher SVV (p = 0.024) and SHV (p = 0.006) variability. Self-positioning along earth-horizontal was more variable in BVD-patients compared to controls (p < 0.001). Again, variability was higher in those with bilaterally-absent oVEMPs (p = 0.032). SVV/SHV-variability was correlated (R = 0.61, slope = 1.06 [95%-CI = 0.80-1.54]) in BVD-patients.
CONCLUSION With variability correlating amongst the different paradigms and with oVEMP-responses, this emphasizes the role of bilaterally intact utricular input for precise perception of gravity.
SIGNIFICANCE In BVD-patients with bilaterally-absent oVEMPs intensified vestibular rehabilitation should be considered.