Ataxia is a neurological syndrome characterised by clumsy and unco-ordinated movement of the limbs, trunk, and cranial muscles. It results from pathology in the cerebellum and its connections, or in the proprioceptive sensory pathways. The list of causes of ataxia is extensive. Typically, when considering a differential diagnosis, ataxia is classified on the basis of whether it is acute, subacute, or chronic. Ataxia may also be classified by age of onset (childhood vs. adult), whether it is hereditary or acquired, and whether it is associated with other clinical features (e.g., seizures, dystonia, vision loss). Degenerative ataxia is the term used to denote ataxia related to cerebellar atrophy of both genetic and unknown causation. Other terms that have been used for this type of ataxia in a broad sense include spinocerebellar degenerations and olivopontocerebellar atrophy, but these are becoming obsolete.
There are no precise data regarding the prevalence of ataxia of all causes.   Epidemiological studies that focus on hereditary types of ataxia have shown a prevalence of around 10 per 100,000 population, and idiopathic ataxia probably outnumbers hereditary cases.  Because there are many causes of degenerative and inherited ataxias, each individual type of ataxia is relatively rare. In the case of genetic forms of ataxia, there are clusters of high incidence of specific types due to founder effects and ethnic and geographical variations in the prevalence of many mutations. 
Assistant Professor of Neurology
The Ohio State University
BKC declares that she has no competing interests.
Dr Barbara Kelly Changizi would like to gratefully acknowledge Dr S.H. Subramony and Dr Hartmut Uschmann, previous contributors to this topic. SHS has received honoraria for lectures given from Athena Diagnostics Company. HU declares that he has no competing interests.
Dean of Medical Faculty
Professor and Chair of Department of Neurology
TK declares that he has no competing interests.
Clinical Professor of Neurology/Director
Ataxia Center and HD Center of Excellence
SLP is the co-author of 2 systematic reviews referenced in this topic.
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