Comparison of bone-conducted vibration for eliciting ocular vestibular-evoked myogenic potentials: forehead versus mastoid tapping.

OBJECTIVE: This study compared bone-conducted vibration (BCV) stimuli at forehead (Fz) and mastoid sites for eliciting ocular vestibular-evoked myogenic potentials (oVEMPs).

STUDY DESIGN: Prospective study.

SETTING: University hospital.

METHODS: Twenty healthy subjects underwent oVEMP testing via BCV stimuli at Fz and mastoid sites. Another 50 patients with unilateral Meniere's disease also underwent oVEMP testing.

RESULTS: All healthy subjects showed clear oVEMPs via BCV stimulation regardless of the tapping sites. The right oVEMPs stimulated by tapping at the right mastoid had earlier nI and pI latencies and a larger nI-pI amplitude compared with those stimulated by tapping at the Fz and left mastoid. Similar trends were also observed in left oVEMPs. However, the asymmetry ratio did not differ significantly between the ipsilateral mastoid and Fz sites. Clinically, tapping at the Fz revealed absent oVEMPs in 28% of Meniere's ears, which decreased to 16% when tapping at the ipsilesional (hydropic) mastoid site, exhibiting a significant difference.

CONCLUSION: Tapping at the ipsilateral mastoid site elicits earlier oVEMP latencies and larger oVEMP amplitudes when compared with tapping at the Fz site. Thus, tapping at the Fz site is suggested to screen for the otolithic function, whereas tapping at the ipsilesional mastoid site is suitable for evaluating residual otolithic function.