Increased Cortical Thickness in Attentional Networks in Parkinson's Disease with Minor Hallucinations.

Caspian M Sawczak,Melanie Cohn,Alexander J Barnett

doi:10.1155/2019/5351749

Abstract

Hallucinations are common in Parkinson's disease (PD). Based on functional brain MRI data, hallucinations are proposed to result from alterations in the dorsal attention network (DAN), ventral attention network (VAN), and default mode network. Using structural MRI data from Parkinson's Progression Markers Initiative (PPMI), we examined cortical thickness in these networks in PD patients with (n=30) and without (n=30) minor hallucinations who were matched on multiple clinical characteristics (e.g., age, sex, education, cognitive diagnosis, MoCA score, medication, disease duration, and severity) as well as healthy controls (n=30) matched on demographic variables. Multivariate analyses revealed mild hallucinations to be associated with thicker cortex in the DAN and VAN, and these effects were driven by the left superior precentral sulcus and postcentral sulcus for the DAN and by the right insular gyrus for the VAN. While these findings may seem at odds with prior work showing grey matter reductions, our patients are in earlier stages of the disease than those in other studies. This is consistent with an inverted U-shape pattern of cortical thickness alterations in other neurodegenerative diseases and warrants further investigations in longitudinal studies tracking brain correlates of PD psychosis progression.

Highlights

Hallucinations are common in Parkinson’s disease (PD) and follow a spectrum of severity
Hippocampal atrophy was found in advanced PD with well-formed hallucinations [11], increased volume was found in patients with minor hallucinations (MH) [12]. We address these conflicting results by investigating cortical thickness alterations in the ventral attention network (VAN), dorsal attention network (DAN), and default mode network (DMN) in recently diagnosed PD patients with MH (PDMH) compared to PD patients with no hallucinations (PDnH), who were matched on multiple demographic and clinical variables, and healthy controls (HC)
The PDnH patients reported no hallucinations on all visits to date. e groups were matched, participantby-participant for age, sex, education, PD severity (MDSUPDRS Part III and Hoehn and Yahr), whether they took PD medications, and cognitive diagnosis (i.e., mild cognitive impairment (MCI) versus intact, determined by Parkinson’s Progression Markers Initiative (PPMI) investigators based on clinical interviews and cognitive testing; neuropsychological data are presented in Supplementary Materials)

Summary

Introduction

Hallucinations are common in Parkinson’s disease (PD) and follow a spectrum of severity (for review, see [1]). One exception is a study demonstrating cortical thinning in the supramarginal, superior frontal, and lateral occipital gyri in a small patient group with well-formed visual hallucinations early in the disease course, but showing no alterations in patients with minor hallucinations (MH) [2]. These findings were not interpreted in the context of the attentional network dysregulation model, the three regions showing cortical thinning are part of the DAN, VAN, and DMN [10]. Based on the attentional network dysfunction model, we hypothesized that the PDMH group would demonstrate cortical thickness alterations in these networks

Methods

Statistical Analysis and Results

Discussion

Conclusion