Diagnostic Value of Vestibular Evoked Myogenic Potential in Acoustic Neuroma

ABSTRACT

BACKGROUND AND OBJECTIVES: Considering vestibular evoked myogenic potential (VEMP) represents functional integration of the inferior vestibular nerve and large proportion of acoustic neuroma (AN) originate from inferior vestibular nerve, VEMP test may provide more valuable information than ABR and the caloric test in terms of evaluating functional integration as well as screening test. Authors hope to clarify such hypothesis and also analyzed if parameters differ between cochlear lesion and retrocochlear lesion. MATERIALS AND METHODS:Authors analyzed the results of VEMP test in 27 patients (10 males and 17 females) of AN and in 24 patients (9 males and 15 females) of unilateral definite Meniere's disease (MD). Right-left difference of interpeak latency (IPL) and interaural amplitude difference (IAD) were used as parameters of VEMP. Longest diameter of the enhanced area was measured as the size of tumor on the axial view of Gadolium enhanced T1 weighted magnetic resonance image. RESULTS: VEMP was abolished in 15 out of 27 AN patients (54.5%). Among the remaining 12 patients, 1 patient showed increased IPL and IAD at same time, while 2 patients exhibited increased IAD. The mean diameter of tumor in the group who showed positive VEMP waves was significantly smaller (0.95 cm) than that of abolished VEMP group (2.22 cm)(p=0.004). Similar tendency was also present in ABR and Caloric test. However, there was not significant difference between MD and AN in the latencies and amplitudes. CONCLUSIONS: VEMP test may not provide diagnostic information in smaller AN, especially less than 1 cm. And parameters of VEMP were not differ between cochlear and retrocochlear lesion. However, VEMP response seems still important for the comprehensive understanding of peripheral cochleovestibular status in addition to ABR and caloric test.