Action fluency in Parkinson's disease: a follow-up study.

The impairment in action fluency task present in Parkinson's disease (PD) patients has been previously interpreted as an indicator of conversion from PD to PD with dementia or as a grammatical deficit for verbs and ascribed to a frontostriatal loop pathophysiology. In the present study, 20 patients with PD without dementia were longitudinally tested with overall cognitive decline scales and semantic, letter, and action fluency tasks in a 24-month follow-up study. In comparison with healthy age-matched controls, PD patients showed a stable and consistent impairment on action fluency without any sign of cognitive decline. Our findings suggest that action fluency task may be an early sign of impairment of frontostriatal circuits in PD and it cannot be considered an indicator of conversion from PD to PD with dementia. Copyright 2005 Movement Disorder Society.