Sporadic adult-onset ataxia.

Sporadic adult-onset ataxia (SAOA) is a nongenetic neurodegenerative disorder of the cerebellum of unknown cause which manifests with progressive ataxia. It is distinguished from hereditary ataxias and from acquired ataxias. SAOA also needs to be differentiated from multiple system atrophy of cerebellar type (MSA-C). Thus, the diagnosis of SAOA can only be made by exclusion. Although cerebellar ataxia is the prominent symptom in SAOA, patients often have additional nonataxia signs, including pyramidal tracts signs, decreased or absent ankle reflexes, sensory disturbances, mainly in the form of reduced vibration sense, and mild urinary symptoms that do not the fulfill the criteria for severe autonomic failure required for the diagnosis of MSA-C. Disease progression in SAOA is considerably slower than in MSA-C. Brain imaging typically shows isolated cerebellar atrophy. Nerve conduction studies provide evidence for polyneuropathy in about one-third of SAOA patients. As the etiology and pathogenesis of SAOA are unknown, there is no specific treatment approach to this condition.