MUSCARINIC ANTAGONISTS IN THE TREATMENT OF ACQUIRED PENDULAR AND DOWNBEAT NYSTAGMUS - A DOUBLE-BLIND, RANDOMIZED TRIAL OF 3 INTRAVENOUS DRUGS

We performed a double-blind, randomized trial of intravenous scopolamine, benztropine, and glycopyrrolate in 7 patients with acquired nystagmus and oscillopsia. Five patients had pendular nystagmus and 2, downbeat nystagmus. We recorded eye movements with a magnetic search coil technique and tested visual acuity and motion perception before and after administration of each drug. Scopolamine reduced nystagmus in all patients. Benztropine was moderately effective and glycopyrrolate had a negligible impact. Visual acuity improved only with scopolamine; motion discrimination and oscillopsia improved significantly with scopolamine and benztropine. Pendular and downbeat nystagmus respond to intravenous antagonists of central muscarinic receptors.