High VOR Gain in Rotary Chair Testing

Question

Answer

This is a little like asking, "Is it possible to be too good?"  Gain values that exceed the upper limit of normal (it is always good to determine whether the upper limit on the display represents mean +/- 1 or 2 standard deviations) can occur for a number of reasons.  On one end of the spectrum, excessively high gains can occur due to patient "state."  That is, extremely anxious patients may generate gain values that exceed the upper limit of normal. This is not abnormal since those patients fail to show evidence of organic disease. On the other end of the continuum patients with midline cerebellar disease can produce disinhibited responses.  In my career I have seen very few of these patients.  The disorder is manifested in caloric testing as well and that phenomenon creates a very nice cross-check. These patients may also show impaired VOR suppression (i.e. impaired fixation suppression).  For me, excessively high rotary chair gain values usually exceed 100% (or 1.0) and must be accompanied by hyperactive caloric responses (see Handbook of Balance Function Testing, or, Balance Function Assessment and Management for those values).