Abnormal Deviation of Subjective Visual Horizontal in Patients with Vestibular Schwannoma

Abstract

This study was aimed to examine the correlation between the results of subjective visual horizontal (SVH) and other vestibular function tests in patients with untreated unilateral vestibular schwannoma (VS). The subjects comprised 40 consecutive patients (17 men, 23 women) with VS who underwent vestibular function tests before surgery and had surgically and histopathologically confirmed unilateral VS. The vestibular function tests included SVH, caloric, and vestibular evoked myogenic potential (VEMP) tests. Of the 40 patients, 31 (77.5%) showed deviation of the SVH toward the affected side down. Especially in 8 patients (20.0%), abnormal deviation (more than 2.2 degrees) toward the affected side down was seen. None of the patients showed abnormal deviation toward the unaffected side down. On the caloric test, the proportion of absent caloric responses and the percent canal paresis in patients with an abnormal SVH was significantly higher than those in patients with a normal SVH. The proportion of abnormal VEMP responses was higher and the percent VEMP asymmetry was smaller in patients with an abnormal SVH than in patients with a normal SVH; however, the differences were not significant. Abnormal results on the caloric test and/or VEMP test were more frequently seen in VS patients with abnormal deviation of the SVH.