Frontal and temporal hyper-perfusion in Parkinson's disease with subjective cognitive decline

Parkinson's disease with subjective cognitive decline (PD-SCD), defined as self-perceived cognitive decline in the absence of objective impairment, is associated with an increased risk of progression to mild cognitive impairment (PD-MCI) and dementia. Cerebral blood flow (CBF) imaging may provide insight into functional alterations preceding measurable cognitive decline.

To characterize regional CBF patterns in PD-SCD and compare them with those in PD with normal cognition (PD-NC) and PD-MCI.

A total of 140 patients with PD were classified as PD-NC (n = 32), PD-SCD (n = 31), or PD-MCI (n = 77) using Movement Disorder Society (MDS) Task Force PD-MCI Level II criteria in conjunction with commonly used assessments of SCD. All participants underwent clinical evaluation, depression assessment, MRI, and ¹²³I-iodoamphetamine single-photon emission computed tomography (SPECT). Whole-brain voxel-wise comparisons of tracer uptake ratios were performed using statistical parametric mapping, adjusting for age, sex, SPECT scanner, and depressive symptom scores.

Compared with PD-NC, PD-SCD demonstrated significantly increased CBF in bilateral frontal and temporal regions (p < 0.01, family - wise error [FWE] corrected) and the left cerebellum (p < 0.05, FWE corrected), despite preserved cognition. PD-MCI exhibited bilateral frontal and temporal hypo-perfusion relative to PD-SCD (p < 0.01, FWE corrected).

PD-SCD is associated with frontal and temporal hyper-perfusion relative to PD-NC and PD-MCI. These regions partially overlap with cortical areas vulnerable to thinning in PD dementia, supporting the hypothesis that hyper-perfusions may reflect compensatory network responses in regions susceptible to structural degeneration.