Vestibular Evoked Myogenic Potentials

Question

Answer

Answer 1:
VEMP norms are presently not well established as they depend on technique (which varies considerably) and are also a function of the brand of equipment and settings used to obtain them. Eventually the manufacturers of evoked potential equipment should provide norms for VEMP's, but this has not yet happened. In the meantime, it seems best to use very conservative norms, which are nevertheless very useful. For the p13 latency, we look for a latency around 11-15 msec, mainly to be sure that the potential really exists. We measure the n23 latency but do not use it for diagnosis. For n23 amplitudes, we consider a potential less than 20 microvolts to be absent, and one greater than 500 microvolts to be unusually large. For symmetry, we consider a potential that is more than twice the size of the other to indicate asymmetry.

Answer 2:
The VEMP test is an auditory evoked potential.

Dr. Timothy C. Hain has been an otoneurologist for 20+ years. He is a Professor of Neurology, Otolaryngology and Physical Therapy at Northwestern University in Chicago, and operates a clinical practice called Chicago Dizziness and Balance. Dr. Hain can be reached at cdb@dizziness-and-balance.com. More details about Dr. Hain's experience with VEMP testing can be found on his web site, www.dizziness-and-balance.com/testing/vemp.html