From the first symptoms, duration is typically between one and three decades, where earlier onset correlates with faster progression.Spinocerebellar ataxia 1, like other SCAs, often causes dysarthria, a motor disorder of speech often manifest as slurring of words; pathological nystagmus, a disorder in which eyes drift involuntarily affecting vision; and gait and balance issues. SCA1 is also commonly present with dysphagia, a swallowing disorder that can cause choking while eating and drinking; and hypermetric saccades, where the eye tends to move faster or further than intended as it tracks an object or moves from one focus to another. As the disease progresses, more severe neurologic symptoms can appear like dysmetria, where limb movements consistently overshoot the desired position; dysdiadochokinesia, where repeated body movements become uncoordinated; or hypotonia, where muscles atrophy. While new symptoms appear as SCA1 progresses,  nystagmus may disappear as eye movements and saccades slow down. Fatality may ultimately be caused by loss of bulbar functions, but complications from symptoms, such as pneumonia from swallowing problems, or trauma from falls, can be fatal as well. The severity and exact phenotype of these symptoms may vary between types of SCA. SCA 1 dysarthria may vary in severity depending on the task and is often associated with more strained, strangled or harsh sounding vocalization than that of other disorders.Because of the significant variance between cases of SCA1, typical signs and symptoms may appear alongside more subtle or rare symptoms.
Several members of the family actively participated in research and the family consented to post mortem examinations of the brains of several deceased relatives. The disease in the Schut family was found to have an autosomal dominant inheritance pattern, and afflicted the spinocerebellar tract. In 1945, John Schut received free medical school education for his service with the United States Army during the second world war and began his own efforts researching hereditary ataxia. : 90–91  Schut developed ataxia like many of his relatives. In 1957, when Schuts ataxia progressed to a point where he was unable to continue work in regular medical practice, he founded the National Ataxia Foundation with lab space donated by Glenwood Hills Hospital in Minneapolis. : 131 John Schuts nephew, Lawerence Schut, also became an ataxia researcher and contributed to localizing a spinocerebellar ataxia gene to the human leukocyte antigen complex in chromosome 6. The success in linking one of these class of diseases to a locus showed that the classification systems in use were unable to distinguish between diseases with many different causes. Many ataxic disorders which were historically identified as Maries ataxia, olivopontocerebellar atrophy or other names were now reclassified as types of spinocerebellar ataxia, each type numbered in order as a new locus was found. In 1993, the gene and a mutation causing spinocerebellar ataxia type 1 was identified. It was the first genetic defect found known to cause an ataxic disorder.