Genetic characterization of cognitive impairment in Parkinson's disease.

Abstract

This scientific commentary refers to ‘Genetic impact on cognition and brain function in newly diagnosed Parkinson’s disease: ICICLE-PD study’, by Nombela et al. (doi: 10.1093/brain/awu201). Although Parkinson’s disease is mainly regarded as a motor disorder, non-motor symptoms are very common. Cognitive impairments occur particularly frequently—even in Parkinson’s disease without dementia. Indeed, one in three patients with Parkinson’s disease displays cognitive impairment at or soon after diagnosis (Muslimovic et al. , 2005), and these impairments progressively worsen and cause dementia in late-stage disease. The relative risk of dementia in patients with Parkinson’s disease varies between 1.7 and 5.9 (Aarsland and Kurz, 2010). Hence, early detection of cognitive impairment and identification of individuals at risk of dementia are major challenges. At present such classifications are usually based on clinical features that have limited prognostic value because of the heterogeneity of patients’ cognitive profiles (Dujardin et al. , 2013). In this issue of Brain , Nombela and colleagues perform a detailed characterization of cognitive impairment in Parkinson’s disease (Nombela et al. , 2014). They show that impairments in tasks involving executive, visuospatial and memory functions are common in newly diagnosed patients, that the impairments are associated with specific abnormalities in regional brain activation, and that regional brain activation is influenced by specific genotypes. Previous research on clinical heterogeneity in Parkinson’s disease by the same group and others gave rise to the dual syndrome hypothesis of cognitive …