Lithium-induced downbeat nystagmus.

We examined six patients who developed blurring or oscillopsia as a result of downbeat nystagmus while being treated with lithium carbonate. Of these six plus six previously described similar patients, all but two developed downbeat nystagmus insidiously as an isolated disorder in the setting of otherwise satisfactory therapeutic control, without clinical or biochemical evidence of acute lithium intoxication. Only six of these 12 patients were able either to reduce or to stop taking lithium, and in only two of these six did the downbeat nystagmus improve or remit.