Objective: To assess resting-state functional connectivity modifications characterizing the frontostriatal and posterior cortical cognitive subtypes in Parkinson’s Disease (PD)

Background: The dual syndrome hypothesis (Kehagia et al., 2013) suggests that two cognitive subtypes exist in mild cognitive impairment (MCI) in PD: a frontostriatal one and a posterior cortical one. The latter is associated with a higher risk of developing dementia. How these PD-MCI subtypes relate to specific resting-state functional connectivity changes has not been characterized yet.

Method: One hundred non-demented PD patients underwent a neuropsychological assessment and 3T MRI (Philips Achieva) in two different centers (Lille, France and Maastricht, Netherlands). Resting-state functional MRI was performed with a T₂*-weighted EPI sequence lasting 10 min (voxel size: 3x3x3 mm³; TR: 2400 ms; TE: 30 ms; matrix size: 64x64x40 voxels; flip angle: 90°). Depending on their cognitive performance, patients were divided into four groups: (a) without cognitive deficits, (b) frontostriatal subtype, (c) posterior cortical subtype, (d) mixed (frontostriatal and posterior cortical) subtype. In order to perform a between-group network-based statistics analysis, we extracted nine well-known cortical and subcortical resting-state functional networks using an independent component analysis (ICA).

Results: The four subtypes were observed with different frequency (35% without cognitive disorders, 13% with frontostriatal subtype, 22% with posterior cortical subtype, 30% with a mixed subtype). Groups differed according to sex, education duration, overall cognition, severity of anxiety symptoms and ongoing treatment with benzodiazepines. Patients with a mixed subtype performed worse than the three other subtypes in all cognitive tests. Moreover, they showed reduced inter-networks functional connectivity compared to patients without cognitive deficits. No other between-group comparison was significant.

Conclusion: As expected, PD-MCI patients with more severe cognitive deficits had reduced inter-networks resting-state functional connectivity. However, the frontostriatal and posterior cortical subtypes did not display functional connectivity changes compared to cognitively normal PD patients. Further studies with higher sample size and with healthy controls will be needed.

References: Kehagia AA, Barker RA, Robbins TW. Cognitive impairment in Parkinson’s disease: the dual syndrome hypothesis. Neurodegener Dis. 2013;11(2):79‑92.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-dual-cognitive-syndrome-in-parkinsons-disease-a-resting-state-functional-connectivity-study/