Treatment of the gravity-dependence of downbeat nystagmus with 3,4-diaminopyridine

Objective: Spontaneous ocular drift in cerebellar downbeat nystagmus typically contains both a gravity-dependent and a gravity-independent component. We specifically examined the effect of the potassium channel blocker 3,4-diaminopyridine, which has been shown to suppress overall vertical ocular drift in patients with downbeat nystagmus, on the gravity-dependent vertical drift component in eleven patients with idiopathic cerebellar ataxia. Methods: Eye movements were recorded at gaze straight ahead and at horizontal and vertical gaze eccentricities in five different head pitch positions, ranging from nose down t…