Time course of vestibular function in patients with menière's disease following vestibular nerve section

Harmonic acceleration rotational test and vestibular autorotation test (VAT) were performed on 8 patients with Menière's disease before and after vestibular nerve section. Sinusoidal rotations of 0.01-0.64 Hz were used in the HA rotational test. VAT was performed at frequencies between 0.5 and 6 Hz. Two weeks after operation, almost all the patients consistently showed response asymmetry toward the healthy ear at all stimulus frequencies and a reduction in sensitivity to rotational stimuli at 0.01 Hz in the HA rotational test. Prior to surgery, the time constant of the vestibulo-ocular reflex (VOR) varied according to the residual vestibular function of each patient. The time constant then dropped to a mean of 4.2 s after the operation. In the VAT, almost all the patients showed a gain reduction at all frequency ranges on the seventh postoperative day. These findings suggest that response asymmetry and gain at 0.01 Hz in the HA rotational test are valuable for evaluating the time course of the compensation of the vestibular function after surgery and that the VOR time constant is useful in detecting whether the vestibular nerve has been sectioned correctly.