Neuropsychological features of early cognitive impairment in Parkinson’s disease

Abstract:

Cognitive impairment can be evident even in the earliest stages of Parkinson's disease (PD). Executive dysfunction due to disruption of dopaminergic frontostriatal circuitry is well recognised, but deficits also occur across other domains, including memory and visuospatial function, and these deficits may have a non-dopaminergic basis. There is growing interest in the concept of mild cognitive impairment in PD, which may have important prognostic implications in terms of predicting the development of dementia. Cognitive impairment in early PD is heterogeneous, and hence particular subtypes of mild cognitive impairment might have particular prognostic significance. This chapter will review the prevalence of neuropsychological deficits in early PD, and discuss whether these deficits have any functional impact on the day to day life of PD patients. We will then consider the most appropriate neuropsychological tools to use in early PD given the limitations of current instruments and difficulties in neuropsychological testing in this patient group. Longitudinal data exploring the evolution of early cognitive deficits over time and their relationship with later occurring dementia will then be discussed. Finally, we will review current knowledge about the underlying pathophysiology of cognitive impairment in early PD, which has important implications for better understanding the neurobiological basis of PD-associated dementia.