Optokinetic response in patients with vestibular areflexia.

Optokinetic nystagmus (OKN) responses (stimuli 40°/s and 60°/s) were evaluated in 121 patients with vestibular areflexia (VA) and were compared with a control group of 99 control subjects matched by age. The mean response levels were significantly higher in the VA group than in the control group: 1.7°/s at 40°/s stimulation, and 4.4°/s at 60°/s. The VA group showed a significantly wider scattering and greater variances and, as a group, they exhibited higher OKN gains than the control subjects. We suggest that the higher gain of OKN responses in VA patients can be attributed to an increased efficiency in signal processing by the cortical optokinetic system. This enhancement may be similar to the enhancement which, in healthy subjects, is produced by "optokinetic training".