Mild cognitive impairment in Parkinson’s disease: the challenge and the promise

This review addresses the literature surrounding Parkinson's disease (PD) and mild cognitive impairment (MCI). It discusses the neuropsychological, pharmaceutical, and pathological overlap, the socioeconomic impact of PD and MCI, and the value of recognizing, understanding, and treating MCI in PD. It is concluded from this review that MCI in PD does exist and should be considered in clinical and research investigations. Due to the lack of accepted clinical criteria, an inclusive operating definition of MCI in PD is proposed. Research guidelines for studying the presence of MCI in PD and evaluating the efficacy of pharmaceutical interventions are also suggested.