A case of periodic alternating nystagmus: with a special reference to the efficacy of baclofen treatment.

A case of periodic alternating nystagmus (PAN), probably of congenital type, was reported. A 25-year-old woman, who has been suffering from cerebral palsy, was referred to our clinic for the consultation of a peculiar nystagmus and intermittent oscillopsia. Electronystagmographic examination revealed that the horizontal nystagmus on straight ahead gaze in the light continuously changed its direction alternately about 110 sec in right direction and about 90 sec in left direction with about 5 sec of an interlude, during which no nystagmus was observed, between each span. Electronystagmographic recording also illustrated that the amplitude and slow phase eye velocity of PAN first increase and then decrease in each span. Since other various kind of examination including neuroradiological examination revealed no special abnormality except for the signs of cerebral palsy, congenital PAN was suspected in this case. Although previous report indicated that baclofen dose not control congenital PAN in contrast to that of acquired type, we tried baclofen in this case. Baclofen reduced the strength of the nystagmus remarkably and patient also recognized the considerable improvement of her oscillopsia. We are of the opinion that the baclofen may improve the strength of congenital PAN and oscillopsia as well as those of acquired type PAN.