Abstract
<h3>Research Objectives</h3> To investigate whether individuals with idiopathic Parkinson disease (PD) are differentiated by early evidence of predominant fronto-striatal or posterior cortical impairment as proposed by the Dual-Syndrome Hypothesis (Kehagia et al., 2013). <h3>Design</h3> Retrospective inception cohort of de novo PD. Participants completed neuropsychological tests, including the Letter Number Sequencing Test (LNS), Benton Judgement of Line Orientation (JoLO), Semantic Fluency Task, and Montreal Cognitive Assessment (MoCA). <h3>Setting</h3> Data used in the preparation of this study were obtained from the Parkinson's Progression Markers Initiative (PPMI) database (www.ppmi-info.org/data). For up-to-date information on the study, visit www.ppmi-info.org. <h3>Participants</h3> 312 individuals with PD (< 2 years of diagnosis) with data available from the baseline visit of the PPMI study and evidence of dopaminergic denervation on a dopamine transporter SPECT scan. <h3>Interventions</h3> Not applicable. <h3>Main Outcome Measures</h3> The fronto-striatal profile was based on impaired performance on the LNS and attention and executive tasks of the MoCA, with relative preservation of semantic fluency and visuospatial functioning. The posterior-cortical profile was based on impaired performance on the JoLO, semantic fluency task, and visuospatial tasks of the MoCA. A priori criteria based on normative data were utilized to group participants into the fronto-striatal or posterior cortical profile. <h3>Results</h3> At baseline, 4.49% of participants met the strict inclusion criteria for the fronto-striatal profile and 32.30% for the posterior cortical profile. <h3>Conclusions</h3> The Dual-Syndrome Hypothesis is a comprehensive theory explaining cognitive heterogeneity in PD. The current study suggests that cognitive profiles may emerge early in the de novo PD stage. Identification of the posterior cortical profile has important clinical implications as it is associated with a higher risk of dementia. <h3>Author(s) Disclosures</h3> The authors have no conflicts of interest.
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