Effect of 3,4-diaminopyridine on the gravity dependence of ocular drift in downbeat nystagmus

Abstract
A 63-year-old woman had a 4-year history of vertical oscillopsia, diplopia, blurred vision, and postural instability. Symptoms increased on downward gaze and considerably more when she bent her head forward. Clinically she showed DBN. In the head forward bending position there was a marked increase of DBN. Except for the tendency to fall backward, the neurologic examination was unremarkable. MRI, CSF, and blood screening were normal. Electronystagmography was normal except for mildly impaired horizontal smooth pursuit. DBN was superimposed on downward vertical smooth pursuit …