Computer analysis of optokinetic nystagmus in patients with spontaneous nystagmus of peripheral vestibular origin.

The bias of slow phase velocity (SPV) of optokinetic nystagmus (OKN) caused by an acute labyrinthine lesion was examined in 8 patients using differnet optokinetic stimulus velocities. In all patients a directional preponderance of OKN-SPV was found corresponding to spontaneous nystagmus. This was due to enhancement of nystagmus SPV to the side of the lesion and depression of SPV in the opposite horizontal direction. The preponderance of OKN on the average increased with the intensity of spontaneous nystagmus and decreased along with recovery. These vestibularly induced differences in OKN-SPV range up to 70%. A differentiation is discussed between OKN preponderances caused by labyrinthine lesions and brain stem lesions.