Treatment of acquired periodic alternating nystagmus with memantine

Abstract

Abstract Purpose To report a patient with acquired periodic alternating nystagmus secondary to sarcoidosis successfully treated with memantine Methods A 43 year old man had a four year history of acquired horizontal periodic alternating nystagmus (PAN) with oscillopsia secondary to sarcoidosis. Visual acuity (VA) was measured and eye movement recordings were performed with an infra‐red eye tracker (Eyelink I, 250 Hz) before and after treatment with 5 mg memantine per day Results The visual acuity (VA) was 6/36 in the right eye and 6/24 in the left eye during maximum nystagmus amplitude. The duration of the right beating and left beating phases was 105‐110 seconds and of the quite phases was 4‐5 seconds. During the quiet phase the nystagmus was insignificant. On memantine the patient became significantly less symptomatic. The right visual acuity improved to 6/6 and the left to 6/4 during the entire cycle of PAN. Before treatment the nystagmus reached a maximum intensity of 11.9°/sec (frequency 3.6 Hz and amplitude 3.3°) during right beating periods and 14.0°/sec (frequency 3.5Hz and amplitude 4.0°) during left beating. Again the quiet phases in between were insignificant in terms of nystagmus. After treatment of 5mg of memantine per day the intensity was reduced to a maximum intensity of 0.41°/sec (frequency 1.54 Hz and amplitude 0.26°) during right beating period and 0.54°/sec (frequency 1.28 Hz and amplitude 0.42°) during left beating. Conclusion We showed for the first time that memantine can reduce PAN dramatically (4% of the original amount). Treatment with memantine should be investigated systematically in PAN.