Relationship Between Iron Distribution in Deep Gray Matter Nuclei Measured by Quantitative Susceptibility Mapping and Motor Outcome After Deep Brain Stimulation in Patients With Parkinson's Disease

Abstract

Background: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves motor deficits in advanced Parkinson's disease (PD) patients, but the degree of motor improvement varies across individuals. PD pathology involves the changes of iron spatial distribution in the deep gray matter nuclei.

Purpose: To explore the relationship between the iron spatial distribution and motor improvement among PD patients who underwent STN-DBS surgery in three regions: substantia nigra (SN), STN, and dentate nucleus (DN).

Study type: Prospective.

Subjects: Forty PD patients (49.7 ± 8.8 years, 22 males/18 females) who underwent bilateral STN-DBS.

Field strength/sequence: A 3 T preoperative three-dimensional spoiled bipolar-readout multi-echo gradient recalled echo and two-dimensional fast spin echo sequences.

Assessment: Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale part III (MDS-UPDRS III) scores were assessed 2-3 days before and 6 months after STN-DBS. The first- and second-order texture features in regions of interest were measured on susceptibility maps.

Statistical tests: Intraclass correlation coefficient was used to determine the consistency of the region of interest volumes delineated by the two raters. Pearson or Spearman's correlation coefficients were used to assess the relationship between motor improvement after DBS and texture features. A P-value <0.05 was considered statistically significant.

Results: MDS-UPDRS III scores were reduced by 59.9% after STN-DBS in 40 PD patients. Motor improvement correlated with second-order texture parameters in the SN including angular second moment (r = -0.449), correlation (rho = 0.326), sum of squares (r = 0.402), sum of entropy (rho = 0.421), and entropy (r = 0.410). Additionally, DBS outcome negatively correlated with mean susceptibility values in the DN (r = -0.400).

Data conclusion: PD patients with a more homogeneous iron distribution throughout the SN or a higher iron concentration in the DN responded worse to STN-DBS.

Level of evidence: 2 TECHNICAL EFFICACY: Stage 1.

Keywords: Parkinson's disease; deep brain stimulation; iron spatial distribution; magnetic resonance imaging; motor improvement; texture analysis.