AUTOSOMAL-DOMINANT CEREBELLAR-ATAXIA TYPE-I - NERVE-CONDUCTION AND EVOKED-POTENTIAL STUDIES IN FAMILIES WITH SCA1, SCA2 AND SCA3

Forty-one patients suffering from autosomal dominant cerebellar ataxia type I (ADCA-I) were subjected to a genotype-phenotype correlation an alysis using molecular genetic assignment to the spinocerebellar ataxi a type 1, 2 or 3 (SCA1, -2 or -3) genetic focus, clinical examination and nerve conduction as well as evoked potential studies. Pyramidal tr act signs, pale discs, and dysphagia were more frequent in SCA1 compar ed with SCA2 and SCA3 patients, while double vision occurred less freq uently. Visual evoked potentials and motor evoked potentials following transcranial magnetic stimulation were abnormal in almost all SCAI pa tients, but only in a minority of SCA2 and SCA3 patients. In contrast somatosensory evoked potentials were delayed or absent in the majority of patients with no significant differences between the mutations. Ab normalities of brainstem auditory evoked potentials were found in abou t half of the patients irrespective of the underlying mutation. In add ition, reduced sensory nerve action potentials, suggesting sensory axo nal neuropathy were found in all three mutations. These findings provi de electrophysiological evidence that pyramidal and visual pathways ar e differentially affected in SCA1, SCA2 and SCA3 patients.