Therapy of downbeat nystagmus: differential effects of aminopyridines on the gravity dependence and gaze holding function

Recently, aminopyridines (AP) have been shown to be an effective therapy for downbeat nystagmus (DBN). Since AP improve both (i) resting discharge and (ii) excitability of floccular Purkinje cells (PC), we investigated the effect of AP on the vertical eye position sensitivity (EPS) and the gravity dependence (GD) in a large group of patients with idiopathic DBN. We recorded vertical ocular drift velocity in gaze straight ahead and different vertical (±10°) and horizontal gaze positions in five pitch positions of the head between prone and supine (including upright) prior and 45 minutes after the ingestion of 3,4…