A case of myotonic dystrophy with impairment of smooth pursuit eye movement

: We reported a 36-year-old woman of myotonic dystrophy with impairment of smooth pursuit eye movement. The patient, whose mother was also affected, had psychomotor retardation from childhood. DNA analysis by Southern hybridization technique showed large DNA fragment (14/8.6 kb). Oculomotor limitation and gaze nystagmus were not observed, and saccadic eye movements were normal. In electrooculography, smooth pursuit eye movements were impaired toward both directions, and interrupted by saccades. The caloric test elicited a satisfactory response, but the visual suppression test produced no suppression. CT scan displayed paraventricular low density area, and MRI showed the multiple foci of high signal intensity in the white matter on T2-weighted images. No changes were detected on CT or MRI in the brainstem and cerebellum. The lesions in the brain are considered to be correlated with smooth pursuit impairment.