To study the earliest stages of cerebellar dysfunction an eye blink test is performed in 18 preclinical carriers of a SCA3 mutation and 16 healthy, age-matched controls. The participants were presented with repeated pairings of an auditory tone with a supraorbital nerve stimulus with a delay interval of 400 ms.
Preclinical carriers acquired significantly less conditioned eyeblink responses than controls and learning rates were significantly reduced. This motor learning defect was, however, not associated with the predicted time to onset.
Eye blink is impaired in preclinical carriers of a SCA3 mutation, as a result of impaired motor learning capacities of the cerebellum and is thus suggestive of cerebellar dysfunction. The eye blink test can be used to detect but probably not monitor preclinical cerebellar dysfunction in genetic ataxias, such as SCA3.