Objectives Although primary dystonia is typically characterized as a movement 
disorder, it is also associated with cognitive alterations in the domain of 
executive functioning which may arise from changes in cortico-basal ganglia 
circuits. Specifically, in comparison to healthy controls, patients with 
dystonia show deficits in neuropsychological tests of cognitive flexibility. 
However, it is unclear whether cognitive inflexibility is caused by the 
pathomechanisms underlying primary dystonia or by confounding factors such as 
depression or symptom-related distraction.Methods The present study aimed to 
eliminate these confounds by examining cognitive flexibility in dystonia 
patients and in patients with similar motor symptoms but without a comparable 
central pathophysiology. Eighteen patients with primary blepharospasm, a common 
form of dystonia affecting the muscles around the eyes, and 19 patients with 
hemifacial spasm, a facial nerve disorder causing similar eyelid spasms, 
completed a computerized version of the Wisconsin Card Sorting Test (cWCST). The 
two groups were further compared on tests of global cognitive functioning, 
psychiatric symptoms, health status, and impulsiveness. Results Blepharospasm 
patients committed significantly more errors on the cWCST than patients with 
hemifacial spasm. Group differences were most pronounced with regard to 
integration errors, a measure of rule-inference processes on the cWCST. 
Integration errors were also associated with impulsiveness in patients with 
blepharospasm. Conclusions Primary blepharospasm is related to deficits in 
cognitive flexibility, even when blepharospasm patients are compared with 
patients who suffer from motor symptoms of non-dystonic origin. Our results 
support the possibility that cognitive inflexibility results from the specific 
pathophysiological processes underlying primary dystonia. (JINS, 2016, 22, 
662-670).