Motorized head impulse rotator in patients with vestibular schwannoma

Motorized head impulse rotator is an effective technique to assess peripheral vestibular function. Approximately a quarter of patients with vestibular schwannoma (VS) had preserved preoperative responses. Vestibular disability could not be predicted based on vestibulo-ocular reflex (VOR) performance during motion stimuli, or in the caloric test.

To explore motorized head impulse rotator for evaluation of angular horizontal VOR in patients with VS, and to compare these responses to those of the caloric test and the symptoms.

We prospectively recorded head and eye position during unpredictable motorized head impulses in 38 patients with VS. We calculated gain and asymmetry of VOR (mean +/- 95% CI), and the results were compared to those of the caloric test and a questionnaire regarding dizziness, hearing and quality of life.

The VOR during motorized impulses was abnormal in 71% of patients. Asymmetry in gain correlated significantly (p < 0.001) with unilateral weakness in the caloric test. Preoperative gain was significantly lowered to 0.83 +/- 0.08 on the ipsilateral side compared to 0.98 +/- 0.06 on the contralateral side. Postoperative gain on the operated side of 0.53 +/- 0.05 was significantly different from preoperative gain (p < 0.001). Findings in vestibular tests did not correlate with subjective sensation of dizziness.