CLINICAL-FEATURES AND NATURAL-HISTORY OF SPINOCEREBELLAR ATAXIA TYPE-1

SCA1 is a dominant spinocerebellar ataxia (SCA) and a multi-systemic s yndrome caused by abnormal expansion of unstable CAG repeat in a novel gene located on chromosome 6p22-p23. We clinically studied 35 Japanes e SCA1 patients who were assumed to have come from a common origin. Th e age at onset ranged from 15-63 years, and significantly correlated w ith CAG repeat units of mutant alleles. Ataxia was the initial symptom , and the majority of patients had a similar history of signs and symp toms. Nystagmus was at first minimal, later attenuated, and a slow sac cade followed. Limb tendon reflexes were mostly hyperactive and depres sed with the development of diffuse amyotrophy. The cardinal feature w as ataxia-hyperreflexia-late slow saccade syndrome with terminal amyot rophy. Although the phenotype of SCA1 overlaps with those of other dom inant SCAs, some facets of the neurological events differ from either SCA2 with ataxia-hyporeflexia-slow saccade syndrome, or early-onset Ma chado-Joseph disease with dystonia-bradykinesia-spasticity syndrome.