Value of rotational tests in the diagnosis of vestibular disease.

Abstract

Caloric irrigation of the external ear canal represents an inadequate vestibular stimulus because the method is not physiologic and the canal irrigation and the heat transfer to the inner ear cannot be well controlled. In rotational testing an accurate acceleration profile can be applied with an appropriate rotating device. A test procedure is presently being used, which consists of constant acceleration at 3°/sec2 for 50 seconds, hold at constant velocity for 240 seconds, followed by a similar deceleration (equivalent to acceleration in the revelse direction) and hold. On-line data reduction of the nystagmus response is accomplished automatically using a simple analog technique. This technique provides a concise presentation (on a standard size sheet of paper) of the total slow phase eye displacement resulting from the primary and secondary responses and enables comparison of the results for both directions of acceleration. Experience with the routine use of rotational testing in a vestibular clinic and the significance of various paterns of response with special emphasis on vestibular adaptation function are discussed.