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

Aminopyridines (AP) have been shown to be an efficient 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 patients with idiopathic DBN. Eye movements towards targets presented in gaze straight ahead and±10° vertically were recorded prior to and 45 minutes after 20mg DAP or 4-AP ingestion in five pitch positions of the head relative to the upright position, i.e. from prone to supine head positions. Head position dep…