Polyneuropathy in autosomal dominant cerebellar ataxias: Phenotype-genotype correlation

Autosomal dominant cerebellar ataxias (ADCAs) are clinically and geneticall y heterogeneous neurodegenerative disorders. The aim of this study was to e valuate electrophysiologically peripheral nervous system involvement in eac h of the groups studied and its correlation with the number of CAG repeats. Forty patients with ADCA were clinically and electrophysiologically invest igated. Thirty-five patients belonged to the ADCA type I group (SCA1, 12; S CA2, 10; SCA3, 13) and five to the ADCA type II group. Axonal sensory or se nsorimotor polyneuropathy was found in 42% of the SCAI patients, 80% of the SCA2 patients, and 54% of the SCA3 patients, whereas electrophysiological studies were normal in all those with ADCA type II. The number of CAG repea ts was significantly higher in SCAI patients with polyneuropathy than in th ose without polyneuropathy (P = 0.01), whereas the reverse was observed in SCA3/MJD (Machado-Joseph disease) patients (P = 0.05). We conclude that axo nal polyneuropathy is often associated with ADCA type I, but its frequency varies according to factors such as the locus responsible and the number of CAG repeats. (C) 1999 John Wiley & Sons, Inc.