Comparing the Results of Video Head Impulse Test in Patients with Peripheral and Central Vestibular System Tumors

Background and purpose: Vestibular Schwannoma (VS) is a lesion in peripheral vestibular system that leads to reduction of Vestibulo Ocular Reflex (VOR) gain and incidence of corrective saccades. Researches showed that the result of Video Head Impulse Test (VHIT) is positive in peripheral vestibular system disorders and negative in central vestibular system disorders. The aim of this study was to evaluate and compare the results of VHIT in patients with vestibular schwannoma and patients with central vestibular system tumors. A descriptive-analytic study was conducted in 12 patients with unilateral VS tumor and 15 patients with unilateral central vestibular system tumors in Iran Gamma-Knife Center (December 2014-September 2015). The patients were selected based on diagnosis of neurosurgeon and their complaints from vertigo, imbalance, and dizziness. Assessment of VHIT was performed using horizontal and vertical head impulses. Finally, the amount of VOR gain and the corrective saccade ratio were evaluated in two groups of patients with tumors. The gain of VOR ≤0.80 was considered as abnormal criterion. Mean VOR gain in effective side was 0.38 in patients with VS tumor, and 0.96 in patients with central vestibular system tumors (P= 0.001). Also, corrective saccades ratio was 30.34 in patients with VS and 3.44 in patients with central vestibular system tumors (P= 0.007). The results of VHIT improved differential diagnosis of peripheral vestibular system tumors from central vestibular system tumors.