Classification of Nystagmus

Nystagmus may be defined as a to-and-fro ocular oscillation, of one or both yes, in which each phase is of equal or near-equal amplitude. The neurophysiological mechanism of nystagmus is not well understood, but hopefully applications of modern single neuron recordings in the brain stem may yield increased understanding (1,2). The physiological uncertainty is reflected clinically; although nystagmus is a common neurological sign, its localizing significance is often a mere indication of dysfunction ""somewhere in the posterior fossa,"" i.e., brain stem and cerebellum. However, certain nystagmus patterns are quite specific, and permit reasonably accurate neuro-anatomical diagnosis. Our approach will be to separate, whenever possible, the specific and non-specific forms of nystagmus on the basis of the clinical appearance and associated signs and symptoms.