Vestibulo-Ocular Reflex in Patients with Meniere's disease Between Attacks

In Meniere's disease, spontaneous nystagmus beating toward the affected ear (ipsilateral nystagmus) is frequently observed especially during vertiginous periods. VOR against horizontal rotation was recorded in 19 patients with Meniere's disease exhibiting ispilateral beating nystagmus, and the dynamic aspect of vestibular function during vertiginous periods was examined by determining VOR gain and directional preponderance (DP). The patients sat on a rotation chair and were passively rotated at about 0.3-0.6 Hz. The maximal head velocity ranged from 80 to 120 deg/s and the duration of rotation from 20 to 30 s. In most patients exhibiting ipsilateral nystagmus, VOR gain toward the affected side was higher than that toward the intact side, indicating that the peripheral vestibular system on the affected side could still respond to head movements and that its dynamic function was increased. This asymmetry disappeared along with disappearance of ipsilateral nystagmus. During the period with contralateral nystagmus, VOR gain toward the affected side became lower than that toward the intact side. These findings indicate that alterations in the dynamic property of the peripheral vestibular system may correlate with the directional change of spontaneous nystagmus. However, the degree of VOR DP (VOR DP%) did not correlate with the slow phase velocity of spontaneous nystagmus, indicating that observation of spontaneous nystagmus alone cannot determine with precision the degree of imbalance in the dynamic aspect of vestibular function.