Involuntary "Voluntary" Nystagmus.

Background: Voluntary nystagmus is a common phenomenon in the general population and is believed to be under voluntary control. Some patients have an eye movement disorder indistinguishable from voluntary nystagmus and yet have no control over these movements.

Methods: Four patients with involuntary eye movements consisting of spontaneous or induced bursts of saccadic eye movements with no intersaccadic interval are described. All eye movements were typical of "voluntary nystagmus," yet they denied any control over the movements. In none of the patients was there any evidence of psychopathology or secondary gain.

Results: Two types of patients with involuntary eye movements that were indistinguishable from voluntary nystagmus are presented. One group of 2 patients had clear neurological disease, whereas another 2 had no evidence of any neurological pathology.

Conclusions: The patterns seen in these patients suggest that there is a spectrum of oculomotor saccadic instabilities that includes voluntary nystagmus on one extreme and ocular flutter on the other. In between these 2 are both normal and abnormal patients with eye movements indistinguishable from ocular flutter/voluntary nystagmus that may or may not be induced by convergence. It is suggested that involuntary "voluntary nystagmus" is a real condition and that psychopathology should be ruled in rather than simply assumed.