Head Angle During Static Position Test

Question

Answer

The main purpose of the static position test is to examine the effect of gravity on the labyrinth. When the patient is placed flat in the supine position, none of the semicircular canals is fully in the plane of gravity. In the standard caloric position, the lateral (horizontal) canals are in the plane of gravity and when the head is turned right or left from this position, the effect is primarily mediated by the lateral canals. I do not see much benefit to placing all three canals partially in the plane of gravity. That is why we do the test primarily from the standard caloric test. It also makes positioning the patient easier. We do not have to move the patient when going from the position to the caloric test. Finally, we can directly compare our position test results in the "supine" position with the baseline shift in the caloric test (another way of saying spontaneous nystagmus).

I am not sure what you use as normal limits for the position test. We use 4 deg/sec in VNG and 6 deg/sec in ENG as the only normal limit. In other words, if the nystagmus slow-phase-velocity is greater than one of those limits in any head position, we consider the finding abnormal. Otherwise, we report the nystagmus but denote it as non-significant/normal. With that criterion, the exact position or number of different head positions tested will not alter the normal limit. Please refer to this article I wrote a couple of years ago that provides justification for the above normal limits: www.otometrics.com/insights_may_2008_std.pdf

Kamran Barin, Ph.D. is the Director of Balance Disorders Clinic at the Ohio State University Medical Center and Assistant Professor, Department of Otolaryngology-Head and Neck Surgery, Department of Speech and Hearing Science, and Biomedical Engineering Program. He received his Master's and Doctorate degrees in Electrical/Biomedical Engineering from the Ohio State University. He has taught national and international courses and seminars in different areas of vestibular assessment and rehabilitation. Kamran Barin is a consultant to Otometrics and provides courses and other educational material to the company.