Spinocerebellar Ataxia (SCA) is a degenerative, sometimes fatal genetic disease associated with parkinsonism, chorea, cognitive impairment, dementia, nystagmus, cerebellar atrophy and seizures, peripheral neuropathy, and blindness, as well as a host of other symptoms.
An estimated 150,000 people in the United States have SCA and researchers have so far identified at least 40 (and counting) strains of the condition. There is no known treatment or cure.
See the NIH rare diseases site for more detail:
Spinocerebellar ataxia (SCA) is a term referring to a group of hereditary ataxias that are characterized by degenerative changes in the part of the brain related to the movement control (cerebellum), and sometimes in the spinal cord. There are many different types of SCA, and they are classified according to the mutated(altered) gene responsible for the specific type of SCA. The types are described using “SCA” followed by a number, according to their order of identification: SCA1 through SCA40 (and the number continues to grow). The signs and symptoms may vary by type but are similar, and may include an uncoordinated walk (gait), poor hand-eye coordination, and abnormal speech (dysarthria). SCA is inherited in an autosomal dominant manner. However, the term “spinocerebellar” may be found with other diseases, such as the autosomal recessive spinocerebellar ataxias (SCAR). Treatment is supportive and based on the signs and symptoms present in the person with SCA.