Utricular function in vestibular neuritis: a pilot study of concordance/discordance between ocular vestibular evoked myogenic potentials and ocular cycloposition.

Vestibular neuritis (VN) can affect utricular afferents. Utricular function can be assessed by ocular vestibular evoked myogenic potentials (oVEMPs) whose abnormalities include weak or absent responses, and ocular cycloposition whose abnormalities include ocular torsion (OT). When studied independently in vestibular neuritis, oVEMPs are abnormal in 61-82% of cases, and OT is present in 72-80% of cases. The similar range of abnormalities suggests the hypothesis that these tests should be concordantly abnormal. We tested this hypothesis by identifying consecutive adult cases of VN in whom both oVEMPs and OT were performed. OT and oVEMP overlapped (both were abnormal) in only 47% of cases. In 40% of cases oVEMPs alone were abnormal, and in 13% of cases, OT alone was present. These results suggest that oVEMPs and OT assess different aspects of utricular function believed to arise from discrete zones of the utricular macula; the former are thought to reflect the activity of extra-striolar afferents (which detect constant acceleration), and the latter reflects the activity of striolar afferents (which detect change in acceleration).