Cognitive Decline in Parkinsonism: From Clinical Phenotypes to the Genetic Background

Background/Objectives: Cognitive impairment often occurs in various parkinsonian syndromes. The course of deficits in cognitive functions ranges from mild cognitive decline to severe deterioration. Affected cognitive domains are also variable. The genetic background of patients exhibiting parkinsonism with concomitant cognitive decline is still elusive. A significant part of current research in Parkinson's disease and other parkinsonian syndromes is targeted towards the genetic aspects of these disorders. The aim of the present review was to summarize existing studies focusing on the investigation of the interplay between genetic data in parkinsonism and associated cognitive symptoms. Methods: A review of English-language articles published between 2000 and 2024 was conducted, focusing on genetic studies of Parkinson's disease and atypical parkinsonian syndromes with cognitive decline, using the databases PUBMED, SCOPUS, and EMBASE. Results: We have selected a clinical phenotype-wise assessment of parkinsonian conditions with cognitive deficits, including typical or early-onset Parkinson's disease, dementia with Lewy bodies, Corticobasal Syndrome, Progressive Supranuclear Palsy, and frontotemporal dementia with parkinsonism. Both typical and atypical parkinsonian syndromes with concomitant cognitive decline were explored. Conclusions: Genetic background likely contributes to the heterogeneity of cognitive impairment in parkinsonian syndromes, with specific mutations linked to distinct cognitive symptoms. The integration of genetic data and a more thorough neuropsychological assessment with clinical, imaging, and biomarkers may enhance diagnosis and enable personalized therapies.