Cognitive correlates of prospective memory in dystonia

Executive dysfunctions are observed in focal dystonia (i.e., blepharospasm and cervical dystonia). Prospective memory (PM) is the ability to remember to carry out intended actions in the future and plays a relevant role in everyday living and quality of life. Although alterations of prefrontal cortex occur in focal dystonia, until now, no study has yet investigated the occurrence of deficit of PM in focal dystonia. Therefore, the aim of the study was to explore PM and its cognitive correlates in cervical dystonia and blepharospasm.

Twenty-seven patients with blepharospasm, 26 patients with cervical dystonia and 30 healthy subjects, matched for demographic features, underwent neuropsychological tests assessing PM, verbal memory, executive functions, and questionnaires assessing subjective prospective and retrospective memory failures, and apathy.

The three groups did not differ on tests assessing verbal memory, executive functions, but they significantly differed on PM tests. In detail, patients with blepharospasm and cervical dystonia performed worse on time-based and recognition tasks than healthy subjects, while no difference on event-based task was found. Regression analysis showed a relationship between a lower score on Modified Card Sorting Test and a reduced performance on time-based, event-based and recognition tasks within focal dystonia group.

The results indicated a selective deficit of time-based PM in focal dystonia, supporting previous evidence of cognitive dysfunctions in dystonic patients. The relationship between impaired time-based PM and poor performance on cognitive flexibility tests might suggest that difficulty in managing two concurrent cognitive demands contributes to impaired time-based PM.