Cognitive impairment in “Other” movement disorders: Hidden defects and valuable clues

There is a group of less‐common movement disorders in which a clear cognitive phenotype coexists alongside the motor abnormality, and the recognition of this co‐occurrence is essential to diagnose these disorders in an early phase. Examples include chorea‐acanthocytosis, Niemann‐Pick type C, some dominant ataxias, and pantothotenate kinase‐associated neurodegeneration. However, also, in some more‐common movement disorders, such as primary dystonia and essential tremor, of which the perception is that these have a more or less pure motor phenotype, cognitive deficits are commonly present, although it is not clear whether these deficits—which may be mild in the more “pure” motor disorders—have a functionally relevant impact. In both scenarios, disruption of relevant frontal‐subcortical loops appears to be key, with the striatum and cerebellum as important (but not exclusive) nodes. © 2014 International Parkinson and Movement Disorder Society