Ocular VEMP Using Bone Conduction Stimuli at the Forehead - A Pilot Study Comparing B250, Minishaker and Tendon Hammer with Vibrometry Validation.

Background: Bone-conduction stimuli in oVEMP testing offer lower stimulus levels and independence of conductive hearing loss but lack a clinically suitable transducer for excitation. A new bone-conduction transducer (B250) has been developed which is easy to attach and can be directly connected to test stations. Objective: To compare, in a pilot investigation B250, Minishaker and Tendon hammer excitation, used for oVEMP and mastoid vibration measurements. Methods: oVEMPs in three subjects were measured using transducers driven by a 250 Hz condensation single sinus cycle and with a Tendon hammer, all applied at forehead Fz/AFz. Corresponding mastoid velocity was measured using a laser Doppler vibrometer (LDV). Results: B250 and Minishaker often produced dual oVEMP peaks with an early n1 (mean latency: 8.8 ms) and a late n2 response (B250: 12.4/Minishaker: 13.3 ms), and with the Tendon hammer response in between. This finding was supported by a reinvestigation of a previous study (n=15). LDV velocity shows several positive peaks for B250 and one positive peak for the Minishaker. The acceleration response has two peaks 4 ms apart for both transducers, which seem to relate to the early and late oVEMP latencies. Conclusion: B250 may serve as a potential alternative, pending validation in larger samples, to the Minishaker at the forehead, but with care to polarity choice and latency interpretation.