Background: Currently in clinical practice and research involving the human vestibular system, an electrodynamic exciter called the B&K 4810 Minishaker is used to elicit the ocular Vestibular Evoked Myogenic Potential (oVEMP). This is due to its high vibratory force output and flat frequency response. However, globally, this device is neither intended for use on humans nor is it an approved medical device. A bone vibrator called the B81 by RadioEar has been recently developed with a higher MPO and lower distortion than the clinic standard RadioEar B71. The aim of the present study is to compare oVEMPs from the Minishaker to the B81 and report the extent of statistical agreement and equivalence, in order to recommend whether the B81 could be used (or not) in clinical practice.

Methods: Participants (healthy adult, n=16,) were tested with the B81 and the Minishaker at four calibrated vibratory force levels on the mastoid in a counter-balanced manner. Six participants were re-tested in order to define within-transducer variability. Grand average oVEMP traces in response to a 500 Hz tone (1-cycle) were generated. Bland-Altman plots were used to assess agreement between oVEMP parameters elicited from each transducer, and statistical equivalence testing was performed, focusing primarily on N10 and N10-P15 amplitudes. Secondary aspects of interest included the electrical artefact, the residual noise and signal-to-noise ratios, and the amplitudes of downstream VEMP response components in different time frames (17-25ms and 25 -60ms).

Results: A priori calibration of force outputs showed that the B81 and the Minishaker were matched to within 1 dB at two out of four stimulus settings (122 dB FL and 127 dB FL). oVEMP grand average traces overlaid matched closely with a mean N10 amplitude of 1.98 µV (± 3.49) and 4.05 µV (± 5.60) for the B81 at 122 and 127 dB FL. The responses elicited from the Minishaker at these levels were 2.68 µV (± 3.54) and 4.23 µV (± 4.37) respectively. Agreement plot results show that the oVEMPs elicited from each transducer differed by 2% on average, with a range of +6% to -4%. Equivalence data showed oVEMPs were statistically significantly equivalent at both 122 dB FL and 127 dB FL (p value = 0.083, p =0.86).

Conclusions: The B81 can be considered to elicit comparable oVEMPs to the Minishaker when calibrated for force output from the mastoid, when amplitude alone is considered. Further research could examine latencies, different frequencies, and different stimuli.