Ocular vestibular-evoked myogenic potentials to bone-conducted vibration in superior vestibular neuritis show utricular function

Abstract

Objective To determine whether the first negative component (n10) of the ocular vestibular-evoked myogenic potential (oVEMP) to bone-conducted vibration (BCV) is due primarily to activation of the utricular macula. Study Design The n10 was recorded in response to brief BCV at the midline of the forehead at the hairline (Fz). If the n10 is due primarily to utricular activation, then diseases that affect only the superior division of the vestibular nerve in which all utricular afferents course (i.e., superior vestibular neuritis [SVN]) should reduce or eliminate n10 beneath the contralesional eye, whereas the n10 beneath the ipsilesional eye and the sacculo-collic cervical vestibular-evoked myogenic potential (cVEMP) on the ipsilesional side should be preserved. Setting A prospective study at a tertiary neurotological referral center. Subjects and Methods The n10 component of the oVEMP was measured in 133 patients with unilateral SVN but with inferior vestibular nerve function preserved, as shown by ipsilesional cVEMPs. Results The n10 to Fz BCV of 133 SVN patients was reduced beneath the contralesional eye relative to the ipsilesional eye so that there was an n10 asymmetry that was significantly greater than the n10 asymmetry in the 50 healthy subjects. In terms of predicting the affected side (shown by canal paresis), using an n10 asymmetry ratio (asymmetry ratio for the relative size of the n10 of the oVEMPs for the two eyes [AR]) of 46.5 percent, the n10 AR has a diagnostic accuracy of 94 percent. Conclusion The n10 component of the oVEMP to BCV is probably mediated by the superior vestibular nerve and so mainly by the utricular receptors. The n10 AR is almost as good as canal paresis in identifying the affected side in patients.