Abnormal Subcortical Volumes and Cortical Thickness in Parkinson's Disease with Impulse Control Disorders

The occurrence of impulse control disorders (ICDs) in Parkinson's disease (PD) is frequently attributed to dopamine replacement therapy. However, not all patients who receive medication develop ICDs. Recent imaging studies have suggested specific neuroanatomical abnormalities in patients with PD and ICD.

This study aims to identify changes in volumes of subcortical structures and cortical thickness specific to patients with PD and ICDs.

A total of 11 patients with PD and ICD (PD_ICD(+)), 15 patients with PD without ICD (PD_ICD(-)), and 15 healthy controls were analyzed in this study. ICDs were diagnosed and quantified using the Questionnaire for Impulsive-Compulsive Disorders in PD-Rating Scale (QUIP-RS). Structural imaging was performed on a 3T scanner; volumes of subcortical structures and cortical thickness were obtained using first in FSL and FreeSurfer.

Significant volume loss of the nucleus accumbens was observed in the PD_ICD(+) group. Several areas of significant cortical thinning were observed in the PD_ICD(+) group in comparison PD_ICD(-) group. Thinning of the left middle temporal gyrus, transverse temporal gyrus, and bilateral temporal poles was observed in the PD_ICD(+) group. No correlations were observed between QUIP-RS scores and areas of cortical thinning.

The PD_ICD(+) group has specific neuroanatomical variations in the nucleus accumbens and temporal lobes, which may contribute to the development of ICD and perhaps predispose a patient to ICDs on exposure to dopamine replacement therapy.