PRIMARY POSITION UPBEAT NYSTAGMUS REVERSED WITH CARBAMAZEPINE

A 16-year old girl presented with primary position upbeat nystagmus (P PUN). MRI showed a small lesion at the perihypoglossal nuclei of the d orsal medulla oblongata. The case was diagnosed as a demyelinating dis ease for its response to prednisone, and the nystagmus decreased after administration of carbamazepine. Primary position upbeat nystagmus mi ght be caused by an abnormal firing of neurons in the nuclei resulting in a tonic imbalance of vertical gaze. Also this is the first report to confirm the attenuation of PPUN by carbamazepine.