Optokinetic and spontaneous nystagmus in children with neurological disorders.

Binocular and monocular optokinetic nystagmus (OKN) was examined with EOG recordings in 26 visually impaired children with neurological disorders, aged 2.5 months to 15 years. Spontaneous and/or latent nystagmus, complicating the assessment of OKN, was seen in 73% of the children. Binocular OKN in 21 patients with positive visual functions was symmetrical in 5 cases, asymmetrical in 12 cases and could not be elicited in 4 patients. Monocular OKN was nearly always asymmetrical, with usually a superiority of the temporal-to-nasal (TN) components. Five blind children, 4 of them cortically blind, showed positive binocular and monocular OKN, suggesting that neural control of OKN in humans may be at least partly independent of the cortex. This, together with results from some of the sighted patients, indicates that in humans, cortical and subcortical contributions to OKN, and particularly to monocular nasal-to-temporal (NT) OKN, may be more complicated than had been thought.