Abstract

Background and Objectives: Rotation test is a widely used method to evaluate the function of the vestibular system. Generally, the head position to be tilted forwards 30° during rotation is preferred in order to bring the horizontal semicircular canals into the plane of rotation, thus ensuring maximum response. However literatures do not provide a clear reference concerning head position during the rotation test. So, we evaluated the vestibuloocular reflex (VOR) induced by sinusoidal rotation in the horizontal plane in the two different head positions: the head tilted forward 30° and with the head upright. Materials and Methods: A total of 20 men with no known neuro-otological disorders and 9 guinea pigs were studied. The rotations of slow harmonic acceleration on various frequencies were performed with the subject’s head in the upright position and in the 30 pitched down position. Computerized electronystagmography in human and magnetic coil in guinea pigs were used to measure the maximum velocity of slow component of horizontal nystagmus and to calculate gain, phase and symmetry of VOR responses. Results: In both groups, results showed no significant differences in gain, phase and symmetry. Conclusion: In the two different head positions, there were no significant differences in gain, phase and symmetry. The posture of head upright is more comfortable for the patient and gives enough response for the evaluation of vestibular function.

• Keywords: Rotation test;Head position;Electronystagmography;Lateral semicircular canal