CE is advantageous over PAGE in that molecular weight measurements like mass spectrometry can be used with analytes, whereas PAGE requires the use of Southern blot to allow comparison to a sequencing ladder. For repeat lengths within the range where interruptions are relevant, assays like CE and PAGE will not determine if the strain is pathogenic and additional testing will be required. Clinical
No formal diagnostic criteria exist for most SCAs, and genetic testing is the only certain diagnostic method, but clinical examination of signs and symptoms may be vital to distinguishing SCAs from non-genetic ataxias, and from other types of genetic ataxias. Clinical examination can also help distinguish between SCA types to some extent, so genetic tests for certain types can be prioritized over others. Diagnosis of SCAs often begins with the detection of symptoms that suggest a cerebellar disorder, like progressive ataxia or dysarthria, or with recognition of similar symptoms to a case identified in the individuals family history, especially in first or second degree relatives. Many laboratory studies can be used to further narrow the potential cause of ataxia; imaging of brain and spinal cord and various electrophysiology exams may be useful for identifying disease phenotypes and blood and urine studies may rule out acquired causes. : 4 When evaluating ataxic disorders and their treatments, there are numerous tests that a neurologist may perform. Tests may be evaluated individually or follow a scale for evaluating the ataxia.
The volume loss can be correlated to severity and duration.An estimated 77% of cases of progressive cerebellar disease are reported to have one or more mental health disorders, and 19% exhibit cognitive disorders. These estimates are consistently higher than the portion with mental health disorders in the general population, but still follow other general patterns, like correlations between depression frequency and sex or age. It is unclear if depression can be linked causally to cerebellar degeneration; one study reports data consistent with depression primarily being a response to the disability, not a symptom of it, while another reports evidence that depression may have a causal link; prevalence of depression varies differently between SCA types than does the rate of progression of disability. Genetics
Spinocerebellar ataxia type 1 is caused by a mutation in the ATXN1 gene. This mutation is passed down through an autosomal dominant inheritance pattern, meaning that the disease does not skip generations, at least one parent must have the disease for the children to inherit it, and that the odds of any given child inheriting SCA 1, regardless of gender or other phenotypes, is 50% if the affected parent is heterozygous. : 26  The ATXN1 gene on chromosome 6 encodes the ataxin 1 protein, which is used in signaling pathways and gene regulation, and is heavily expressed in Purkinje neurons. The coding region for Ataxin 1 (6p22.3) contains a polyglutamine tract of variable length.