Vestibular Evoked Myogenic Potential (VEMP) detects lesion of -

Vestibular Evoked Myogenic Potentials The vestibular evoked myogenic potential (VEMP) are short latency electro myograms that are evoked by acostic stimuli in high intensity and recorded from surface electrodes over the tonically contracted sternocleido mastoid muscle. The origin of VEMP is the saccule. The response pathway consists of: – Saccule; Inferior Vestibular Nerve, Lateral Vestibular Nucleus, Lateral Vestibulospinal Tract and Sternocleidomastoid muscle. The test provides diagnostic information about saccular and/or inferior vestibular nerve function. An intact middle ear is required for the response quality. Waveform of the response The VEMP waveform is characterised by a Wave I – positive peak at 13-15 (p13) Wave II – negative peak at 21-24 ms (p23) Peak to peak amplitude of p13-23 is measured and asymmetries between the right and left side is noted (by calculating asymmetry ratio AR) Abnormal AR is seen a case of: Saccular hydrops (AR > 36%) Vestibular schwannoma orignating from inferior vestibular nerve. Vestibular neuronitis Superior canal dehiscence syndrome.