Progress and Prospects in Parkinson's Research/Symptoms/Ataxia

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Ataxia
Lack of voluntary coordination of muscle movements

The following references are relevant:-

Nocera et al Impaired Step Up/Over in Persons With Parkinson’s Disease

Paquette et al (2011)  Walking in circles: navigation deficits from Parkinson's disease but not from cerebellar ataxia 

Chaturvedi and Flint (2013) '' Mitochondrial Diseases of the Brain. ''