Maculopathy has been reported in rare cases, and may be linked effects from the mutation on the ATXN1 locus on genes in neighboring loci. Task specific dystonias have been reported in individual cases, often in the form of writers cramps or cervical dystonia.SCAs can also be detected before serious atrophy with electrophysiologic techniques, using electrodes on the scalp to detect changes in electric potential within the brain in response to sensations or movements. Individuals with SCA1 often exhibit abnormal brainstem auditory evoked potential, including prolonged latency and absent or poorly defined waveforms, with one study reporting 73.3% of test subjects exhibiting abnormalities. The same study also found abnormalities in visual evoked potential and median somatosensory evoked potential in some SCA1 persons. These results were similar to those exhibited in other SCAs and differences between the SCAs were not statistically significant, so electrophysiologic techniques cannot replace genetic testing for specific diagnoses of SCAs.All SCAs cause atrophy in various neural tissues that are detectable using magnetic resonance imaging, computed tomography, or other imaging techniques. In SCA1 some degradation in the grey matter of the cerebellum and brain stem can sometimes be detected in presymptomatic individuals with the expansion in ATXN1. Typically, grey matter loss can be observed in cerebellar vermis in all lobules of the cerebellum and in the paramedian portions of both hemispheres. White matter loss can also be observed in the middle cerebellar peduncles.
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.