Properties of cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs) evoked by 500Hz and 100Hz bone vibration at the mastoid.

Objective: To define and compare the input–output properties of 500 Hz and 100 Hz bone-conducted (BC) transmastoid stimulation when evoking cVEMPs and oVEMPs. The findings for 500 Hz were compared with those previously reported for air-conducted (AC) 500 Hz stimulation.Methods: Twelve healthy subjects (18–57 years old) participated in this study, with simultaneous recordings of cVEMPs and oVEMPs bilaterally. Initial intensities of 138 dB (FL) were used and then reduced in 3 or 6 dB increments to 105 dB.Results: For BC 500 Hz, like AC 500 Hz, the relationship between the stimulus and reflex output fitted a power law for most peaks, but not the initial peak of the oVEMP. Some of the subjects did not have early crossed oVEMP responses for BC 500 Hz but all did for 100 Hz. For BC 100 Hz, while the initial waveforms were similar, many of the peaks showed a tendency to saturate at the higher intensities. For both BC 500 Hz and 100 Hz, the initial (contralateral) oVEMP peaks had a higher threshold than for the (ipsilateral) cVEMP responses although this difference was more marked for 500 Hz.Conclusions: BC 500 Hz shows similar properties to AC 500 Hz, consistent with an overlapping spectrum of afferents being excited by both, with bilateral effects for the BC stimulus. BC 100 Hz evokes more non-vestibular peaks, presumably from muscle afferents, for the SCM recordings but is a more reliable method of evoking the early crossed potentials of the oVEMP.Significance: BC 500 Hz is a useful adjunct to the AC 500 Hz stimulus and has similar properties. The BC 100 Hz stimulus may be a more reliable method of evoking the early crossed oVEMP responses