Dementia and mild cognitive impairment in Parkinson's disease: a review

Introduction. The cognitive disorders in Parkinson's disease (PD) have traditionally been associated with the presence of dementia in later stages of the disease. Recent studies, however, consider that cognitive impairment can appear as of early stages. Knowing the cognitive profile of PD furthers our understanding of the clinical phenotype, making it easier to reach a timely diagnosis and favouring intervention on the symptoms from the initial stages. Aim. To present a review of the literature on mild cognitive impairment (MCI) and dementia associated with PD. Development. Several studies report that patients with PD who have a prolonged time to progression develop dementia. Yet, there have also been reports claiming that, as of the early stages, patients can present subtle cognitive alterations known as MCI. The initial neuropsychological profile is mainly of a non-amnesic type, characterised by executive dysfunction, alterations affecting attention, operative memory deficit and faulty retrieval of information. When patients develop dementia, disorders will arise in the storage of information, in semantic fluency, and in visuospatial and visuoperceptual skills. Currently there are criteria available for diagnosing the MCI and dementia associated with PD, as well as valid reliable instruments for detecting those disorders. Conclusions. Cognitive symptoms are frequent in PD. From the initial stages of the disease onwards patients may present MCI that is mainly characterised by a fronto-subcortical cognitive profile, whereas dementia usually develops at later stages, when a pattern of posterior cortical cognitive disorder is also observed.