Acquired pendular nystagmus in multiple sclerosis: an examiner-blind cross-over treatment study of memantine and gabapentin

A prospective examiner-blind, cross-over study was conducted to compare the efficacy of memantine (40 or 60 mg/day) and gabapentin (1,200 mg/day) as therapy for acquired fixational pendular nystagmus (APN) in 11 patients with multiple sclerosis. APN was documented in 20 eyes by electrooculography (EOG). The primary objective of the study was an at least 50% reduction in amplitude and/or frequency of APN compared with baseline values in EOG. This aim was reached for 17 of 20 APN-affected eyes with memantine 40–60 mg and for 11 eyes with gabapentin up to 1,200 mg. A complete cessation of APN was achieved in eight eyes (four patients) with memantine 40 mg and in a further four eyes (two patients) with memantine 60 mg. One patient achieved the same benefit with memantine 40 mg and gabapentin. In two other eyes APN completely subsided with gabapentin 1,200 mg only, but not with memantine. Near visual acuity, a secondary outcome parameter, improved by at least 0.1 in 11 of 17 eyes treated with memantine and in 8 out of 16 eyes treated with gabapentin. In summary, memantine and gabapentin are safe and effective treatment options for APN.