# Nucleus Basalis of Meynert Volume and Cognitive Impairment in Parkinson’s Disease Before and After Deep Brain Stimulation of the Subthalamic Nucleus

## TL;DR

This study finds that a smaller nucleus basalis of Meynert is linked to Parkinson’s disease dementia but not to cognitive decline after brain stimulation.

## Contribution

The study identifies a specific association between NBM volume and Parkinson’s disease dementia, not previously confirmed in this context.

## Key findings

- Smaller NBM volume was significantly associated with Parkinson’s disease dementia at baseline.
- No link was found between NBM volume and cognitive decline after subthalamic nucleus DBS.
- NBM volume did not correlate with baseline cognitive scores or changes in neuropsychological performance.

## Abstract

Objectives: To investigate whether a smaller volume of the nucleus basalis of Meynert (NBM) is associated with (1) preoperative cognitive impairment and (2) cognitive decline six months after deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson’s disease (PD), using detailed neuropsychological assessment (NPA). Methods: PD patients from the GALAXY and DBS-MODE study were included if they had a preoperative MRI and NPA. NBM volume was measured using voxel-based morphometry. Regression analyses were conducted to assess associations between NBM volume and (1) global NPA scores at baseline, (2) baseline cognitive categories (i.e., normal cognition, mild cognitive impairment (MCI) and Parkinson’s disease dementia (PDD)), (3) change in NPA score and (4) cognitive decline based on the reliability change index six months after STN DBS. Results: For 129 patients, NBM volume was significantly associated with baseline cognitive categories (χ2 = 42.4, p < 0.001). However, smaller NBM volume appeared to be associated only with PDD (B = −2.2, p = 0.036), not with MCI. In 103 patients, no association was found between NBM volume and NPA score at baseline, change in NPA score nor cognitive decline six months after STN DBS. Conclusions: Smaller NBM volume appears to be associated with PDD at baseline, but not with cognitive decline six months after STN DBS.