Despite there being so many different variations, SCA is actually pretty rare. Even so, it is one of the most common causes of genetic ataxia. Even among people with no family history who develop ataxia for no other clear reason, a new SCA mutation can be found about 20 percent of the time.
What Causes SCA?
SCA is due to a genetic mutation. Many types are due to so-called expansion mutations, in which several nucleotides (usually cytosine, adenosine, and guanine) repeat more than is found in healthy people. In the common form involving three nucleotides repeating, this is called a trinucleotide repeat. The result of that repetition is that a mutated form of protein is expressed, leading to disease symptoms.
Spinocerebellar ataxia is usually inherited in an autosomal dominant fashion, meaning that if one of the parents has the disorder, there is about a 50 percent chance that a child will have the disease as well.
As the name spinocerebellar ataxia suggests, the disease afflicts the cerebellum and more. The brainstem can also waste away (atrophy), especially in SCA types 1, 2, and 7. The regions of the atrophy often control eye movements, leading to abnormal findings when a neurologist performs their physical exam.
What Is the Prognosis in Spinal Cerebellar Atrophy?
Spinocerebellar ataxias due to repeat expansion mutations usually become sick in middle age. In addition to ataxia, other neurological findings are often present depending on the variant of SCA. In general, the longer the repeat is, the younger the patient will be when the symptoms come on, and the more rapid the disease progression.
In general, SCA type 1 is more...