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).
Keywords: Blepharospasm; Cognitive flexibility; Executive functioning; Hemifacial spasm; Primary dystonia; Rule inference; Set shifting; Wisconsin Card Sorting Test.