Nystagmus-sensation dissociation in spinocerebellar degeneration.

To study nystagmus-sensation dissociation (NSD), i.e. caloric nystagmus without the sensation of vertigo, in patients with spinocerebellar degeneration (SCD).The neuro-otological and neuro-radiological records of 179 patients clinically diagnosed as having SCD (91 males, 88 females; age range 20-89 years) and 48 patients diagnosed as having peripheral vestibular disorders (15 males, 33 females; age range 21-80 years) were reviewed. Subjects underwent caloric tests using cold water (20 degrees C) in a totally dark room. Immediately after each test session, subjects were asked if they had experienced spinning or moving sensations during the test. Maximum slow phase eye velocities (SPEVs) were measured using electronystagmography.Among patients with peripheral vestibular disorders, all patients with SPEVs > 15 degrees/s experienced spinning or moving sensations during testing. Among the 179 patients with SCD, 21 (39 sides) showed maximum SPEVs > 15 degrees/s without spinning or moving sensations. In particular, 8 patients (10 sides) had maximum SPEVs > 25 degrees/s without spinning or moving sensations. Common lesions in the cerebral cortex could not be detected using either MRI or single-photon emission CT.Patients with SCD may also have NSD, which may be attributable to subcortical lesions in the ascending pathways to the vestibular cortex.