Oculomotor involvement in myotonic dystrophy type 2.

Oculomotor function has not been studied in patients with myotonic dystrophy type 2 (DM2). We report the presence of rebound nystagmus in seven of eight patients with DM2 in the absence of a structural brainstem or cerebellar lesion. The rebound nystagmus observed in these patients is very suggestive of ocular myotonia, and examination of patients using video-Frenzel goggles may be a useful method for diagnosing myotonia of the extraocular muscles.