SLOW BUILDUP OF OPTOKINETIC NYSTAGMUS ASSOCIATED WITH DOWNBEAT NYSTAGMUS

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  • 1 January 1979
    • journal article
    • research article
    • Vol. 18  (6) , 622-629
Abstract
Eye movement recordings in 2 patients with downbeat nystagmus demonstrated an unusual finding of severely impaired smooth pursuit and relatively unimpaired optokinetic nystagmus (OKN). OKN was characterized by a remarkable, slow build-up of slow-component velocity, similar to that in afoveate animals. Optokinetic after-nystagmus (OKAN), or transient persistence of nystagmus after cessation of visual stimulation, typical of the optokinetic response of normal human subjects, was preserved in these patients. The normal contribution of smooth pursuit to the ocular motor response to rotation of the visual environment can be selectively removed by a lesion at the level of the craniocervical junction.