Ipsi vs Contra Stimulation of the VEMP

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Answer

Good question. There are some good studies addressing whether the VEMP is exclusively an ipsilateral response, or if there may be some contribution from the contralateral sternocleidomastoid muscle when you record from the ipsilateral side. This is difficult to answer definitively because much of the literature is in conflict. Akin and Murnane (2001) have shown some convincing data to say that the VEMP is mediated by an ipsilateral pathway, making it an ipsilateral-only response.

I think data that says it may be a bilateral response may have a contamination effect from the ground electrode. There truly is no neutral site when you place an electrode on the head. I think perhaps when a smaller amplitude is recorded, for example, a right sternocleidomastoid response when contracting the left and stimulating the left, then it just may be artifact contributed by the ground electrode.

Akin, F.W., Murnane, O.D. (2001). Vestibular evoked myogenic potentials: preliminary report. Journal of the American Academy of Audiology, 12, 445-452.

Dr. Ackley is Director of Audiology at Gallaudet University and former department chair at the University of Northern Colorado and Associate Professor at Colorado State University prior to that. He had an electrophysiological assessment private practice in Colorado from 1987-2000, and he currently directs the Gallaudet Electrophysiology and Balance Center. He has done extensive research on vestibular evoked myogenic potential (VEMP) assessment of Deaf and hard-of-hearing subjects during his tenure at Gallaudet.