From OMIM
The autosomal dominant cerebellar degenerative disorders are generally referred to as 'spinocerebellar ataxias,' (SCAs) even though 'spinocerebellar' is a hybrid term, referring to both clinical signs and neuroanatomical regions (Margolis, 2003). Neuropathologists have defined SCAs as cerebellar ataxias with variable involvement of the brainstem and spinal cord, and the clinical features of the disorders are caused by degeneration of the cerebellum and its afferent and efferent connections, which involve the brainstem and spinal cord (Schols et al., 2004; Taroni and DiDonato, 2004). Historically, Harding (1982) proposed a clinical classification for autosomal dominant cerebellar ataxias (ADCAs). ADCA I was characterized by cerebellar ataxia in combination with various associated neurologic features, such as ophthalmoplegia, pyramidal and extrapyramidal signs, peripheral neuropathy, and dementia, among others. ADCA II was characterized by the cerebellar ataxia, associated neurologic features, and the additional findings of macular and retinal degeneration. ADCA III was a pure form of late-onset cerebellar ataxia without additional features. SCA1, SCA2 (183090), and SCA3, or Machado-Joseph disease (109150), are considered to be forms of ADCA I. These 3 disorders are characterized at the molecular level by CAG repeat expansions on 6p24-p23, 12q24.1, and 14q32.1, respectively. SCA7 (607640), caused by a CAG repeat expansion in the ATXN7 gene (607640) on chromosome 3p13-p12, is a form of ADCA II. SCA5 (600224), SCA31 (117210), SCA6 (183086), and SCA11 (600432) are associated with phenotypes most suggestive of ADCA III. However, Schelhaas et al. (2000) noted that there is significant phenotypic overlap between different forms of SCA as well as significant phenotypic variability within each subtype. Classic reviews of olivopontocerebellar atrophies and of inherited ataxias in general include those of Konigsmark and Weiner (1970), who identified 5 types of olivopontocerebellar atrophy, Berciano (1982), Harding (1993), Schelhaas et al. (2000), and Margolis (2003).  http://www.omim.org/entry/164400

From MedlinePlus Genetics
Spinocerebellar ataxia type 1 (SCA1) is a condition characterized by progressive problems with movement. People with this condition initially experience problems with coordination and balance (ataxia). Other signs and symptoms of SCA1 include speech and swallowing difficulties, muscle stiffness (spasticity), and weakness in the muscles that control eye movement (ophthalmoplegia). Eye muscle weakness leads to rapid, involuntary eye movements (nystagmus). Individuals with SCA1 may have difficulty processing, learning, and remembering information (cognitive impairment).

Over time, individuals with SCA1 may develop numbness, tingling, or pain in the arms and legs (sensory neuropathy); uncontrolled muscle tensing (dystonia); muscle wasting (atrophy); and muscle twitches (fasciculations). Rarely, rigidity, tremors, and involuntary jerking movements (chorea) have been reported in people who have been affected for many years.

Signs and symptoms of the disorder typically begin in early adulthood but can appear anytime from childhood to late adulthood. People with SCA1 typically survive 10 to 20 years after symptoms first appear.  https://medlineplus.gov/genetics/condition/spinocerebellar-ataxia-type-1