In most patients with adult-onset progressive ataxia, the condition manifests without an obvious familial background. The classification and correct diagnosis of such patients remain a challenge, because almost the entire spectrum of non-genetic and genetic causes of ataxia has to be considered. A wide range of potential causes of acquired ataxia exist, including chronic alcohol use, various other toxic agents, immune-mediated inflammation, vitamin deficiency, chronic leptomeningeal deposition of iron leading to superficial siderosis, and chronic CNS infection. Mutations in single genes can also underlie sporadic ataxia in adults. Finally, patients might have a sporadic degenerative disease, such as multiple system atrophy of cerebellar type or sporadic adult-onset ataxia of unknown aetiology. The definition of clinical criteria and delineation of characteristic MRI features have greatly facilitated the early and correct recognition of sporadic ataxias. In addition, specific serological and genetic markers are available that allow a definite diagnosis in many cases.
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