Video Head Impulse Test to Preoperatively Identify the Nerve of Origin of Vestibular Schwannomas

Abstract

AbstractBACKGROUNDIdentification of the nerve of origin in vestibular schwannoma (VS) is an important prognostic factor for hearing preservation surgery. Thus far, vestibular functional tests and magnetic resonance imaging have not yielded reliable results to preoperatively evaluate this information. The development of the video head impulse test (vHIT) has allowed a precise evaluation of each semicircular canal, and its localizing value has been tested for some peripheral vestibular diseases, but not for VS.OBJECTIVETo correlate patterns of semicircular canal alteration on vHIT to intraoperative identification of the nerve of origin of VSs.METHODSA total 31 patients with sporadic VSs were preoperatively evaluated with vHIT (gain of vestibule-ocular reflex, overt and covert saccades on each semicircular canal) and then the nerve of origin was surgically identified during surgical resection via retrosigmoid approach. vHIT results were classified as normal, isolated superior vestibular nerve (SVN) pattern, isolated inferior vestibular nerve (IVN) pattern, predominant SVN pattern, and predominant IVN pattern. Hannover classification, cystic component, and distance between the tumor and the end of the internal auditory canal were also considered for analysis.RESULTSThree patients had a normal vHIT, 12 had an isolated SVN pattern, 5 had an isolated IVN pattern, 7 had a predominant SVN pattern, and 4 had a predominant IVN pattern. vHIT was able to correctly identify the nerve of origin in 89.7% of cases (100% of altered exams).CONCLUSIONThe pattern of semicircular canal dysfunction on vHIT has a localizing value to identify the nerve of origin in VSs.