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The relation between cognition and motor dysfunction in drug-naive newly diagnosed patients with Parkinson's disease§

Authors


  • Funding agencies: This study was supported by grants from the Swedish Medical Research Council, the Parkinson Foundation in Sweden, the Swedish Association of Persons with Neurological Disabilities, Umeå University, Västerbotten County Council (ALF), the King Gustaf V and Queen Victoria Freemason Foundation, the Swedish Brain Foundation, and the Lions Clubs Sweden's Foundation for Research in Age-Related Diseases.

  • Relevant conflicts of interest/financial disclosures: Lars Forsgren serves on scientific advisory boards for Pfizer and UCB and receives research support from the Parkinson Foundation, King Gustaf V and Queen Victoria Freemason Foundation, the Kempe Foundation, Västerbotten County Council, Umeå University, and the Swedish Medical Research Council.

  • §

    Full financial disclosures and author roles may be found in the online version of this article.

Abstract

Recent studies have reported cognitive decline to be common in the early phase of Parkinson's disease. Imaging data connect working memory and executive functioning to the dopamine system. It has also been suggested that bradykinesia is the clinical manifestation most closely related to the nigrostriatal lesion. Exploring the relationship between motor dysfunction and cognition can help us find shared or overlapping systems serving different functions. This relationship has been sparsely investigated in population-based studies of untreated Parkinson's disease. The aim of the present study was to investigate the association between motor signs and cognitive performance in the early stages of Parkinson's disease before the intake of dopaminergic medication. Patients were identified in a population-based study of incident cases with idiopathic parkinsonism. Patients with the postural instability and gait disturbances phenotype were compared with patients with the tremor-dominant phenotype on demographics and cognitive measures. Associations between cognitive and motor scores were investigated, with age, education, and sex controlled for. Bradykinesia was associated with working memory and mental flexibility, whereas axial signs were associated with episodic memory and visuospatial functioning. No significant differences in the neuropsychological variables were found between the postural instability and gait disturbances phenotype and the tremor phenotype. Our results indicate a shared system for slow movement and inflexible thinking that may be controlled by a dopaminergic network different from dopaminergic networks involved in tremor and/or rigidity. The association between axial signs and memory and visuospatial function may point to overlapping systems or pathologies related to these abilities. © 2011 Movement Disorder Society

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