Mild behavioral impairment is linked to worse cognition and brain atrophy in Parkinson disease

Abstract

Objective: To evaluate the associations of mild behavioral impairment (MBI) with cognitive deficits and patterns of gray matter changes in Parkinson disease (PD).

Methods: Sixty patients with PD without dementia and 29 healthy controls underwent a cognitive neuropsychological evaluation and structural MRI scan. MBI was evaluated with the MBI Checklist (MBI-C), a rating scale designed to elicit emergent neuropsychiatric symptoms in accordance with MBI criteria. We divided the patients with PD into 2 groups: 1 group with high MBI-C scores (PD-MBI) and the other with low MBI-C scores (PD-noMBI).

Results: Among 60 patients with PD, 20 were categorized as having PD-MBI (33.33%). In healthy controls, no participants met the MBI cut-point threshold. The PD-MBI group had significantly lower Montreal Cognitive Assessment and z scores in all 5 domains and the global score compared to healthy controls and those with PD-noMBI. In addition, all cognitive domains except language and global cognition negatively correlated with the MBI-C total score in all patients with PD. For cortical structures, the PD-MBI group revealed middle temporal cortex thinning and decreased volume compared with the PD-noMBI group, and decreased volume in this area negatively correlated with the MBI-C total score.

Conclusions: The impaired cognitive function over all domains and atrophy in the temporal area in the PD-MBI group are in line with posterior cortical circuit deficits in PD, which have been associated with a faster rate of progression to dementia. These initial results suggest that MBI might be an early and important marker for incident cognitive decline and dementia in patients with PD.

Figure 1. Cortical regions showing atrophy in PD-MBI compared to PD-noMBI and correlation with MBI-C total score

The PD-MBI group with Parkinson disease (PD) with mild behavioral impairment (MBI) showed (A) thinning and (B) decreased volume in the right middle temporal cortex compared to the PD-noMBI group. (C) The decreased volume in the right middle temporal cortex correlated significantly with MBI Checklist (MBI-C) total score. RH = right hemisphere.

Figure 2. Cortical regions showing atrophy in PD-noMBI and PD-MBI compared to HCs

The PD-MBI group with Parkinson disease (PD) with mild behavioral impairment (MBI) showed cortical atrophy in various regions of (A) thickness, (B) volume, and (C) surface area. The PD-MBI group had thinning in the left parahippocampal cortex and decreased volume and surface area in the right precuneus and decreased volume in the right lingual cortex and lateral frontal pole compared to healthy controls (HC). The PD-noMBI group revealed (D) decreased volume and (E) surface area in the left inferior and right superior parietal lobules compared to HCs. LH = left hemisphere; RH = right hemisphere.