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.
Conclusions::
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.
Keywords: nystagmus • eye movements • drug toxicity/drug effects