Visual gravitational vertical perception in peripheral vestibular hypofunction

Conclusions: Rise time in the estimation of the gravitational vertical in the head tilt response (HTR) test is increased in patients with peripheral vestibular lesions and residual chronic dizziness. Objective: Assessment of the perception of the gravitational vertical in patients with peripheral vestibular lesions through the HTR. Methods: HTR was studied in 12 patients with peripheral vestibular lesion, 8 clinically with chronic dizziness and 4 without it; 23 normal subjects were studied as control group. Two parameters of the HTR were assessed, rise time and steady-state error to characterize a dynamical system step response. The Kolmogorov-Smirnov test (alpha = 5%) was used to verify normal distribution (steady-state error, p = 0.53; rise time, p = 0.88). The three sigma ellipse was calculated for the control group. ROC curves were used to measure the sensitivity and specificity of these parameters. Results: Rise time showed increased values in peripheral vestibular lesion patients with chronic dizziness. Two-dimensional analysis (rise time vs steady-state error) allows a better discrimination between patients with peripheral vestibular hypofunction with chronic dizziness and the rest of the studied population.