Motoric impairment versus iron deposition gradient in the subthalamic nucleus in Parkinson's disease

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

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.

Modified Iron Deposition in Nigrosomes by Pharmacotherapy for the Management of Parkinson’s Disease

Background: Increased iron deposition in nigrosome as assessed by susceptibility-weighted imaging (SWI) is involved in the pathogenesis of Parkinson’s disease (PD). This study investigated the effects of antiparkinson drugs on iron deposition in the nigrosome of PD patients.

Methods: Based on the retrospective analysis of clinical data, alterations in iron deposition in the substantia nigra were investigated in 51 PD patients across different types of therapies and in nine Parkinson-plus syndrome patients. The Movement Disorder Society revision of the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) Part Ⅲ/Ⅳ (UPDRS Ⅲ/Ⅳ) was utilized to evaluate motor function and complications. SWI (slice = 0.6 mm) was used to detect iron deposition in the nigrosome and substantia nigra. Nigrosome loss was scored on a 1-point nigrosome visibility scale. Visual assessment of dorsolateral nigral hyperintensity (DNH) was separately performed for each side of the nigrosome with SWI.

Results: Increased UPDRS Ⅲ scores were correlated with low nigrosome scores based on correlation analysis at a disease duration of 6–12 months (r = −0.8420). The loss of the nigrosome on SWI was clearly inhibited in PD patients with a 3–5-year duration of administration of antiparkinson medications compared with no treatment. Decreased UPDRS Ⅲ scores and increased nigrosome scores were observed in the regular treatment of PD patients with a 6–7-year disease duration. For patients with Parkinson-plus syndromes, such as multiple system atrophy, iron accumulation was apparent in the corpus striatum and substantia nigra compared with that for patients with progressive supranuclear palsy.

Conclusions: Early and regular treatment with antiparkinson drugs not only alleviates the chance of PD disability but also prevents the loss of DNH, namely, iron accumulation in the nigrosome.