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.
This type can be stable or unstable and may require surgery. [1]

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References
This article incorporates text in the public domain from page 99 of the 20th edition of Grays Anatomy (1918)

External links
Netter, Frank. Atlas of Human Anatomy Archived 2017-11-20 at the Wayback Machine, "High Cervical Spine: C1-C2"