Topographical differences of brain iron deposition between progressive supranuclear palsy and parkinsonian variant multiple system atrophy.

OBJECTIVE: There have been various studies showing increased iron levels in parkinsonian disorders. The purpose of this study was to demonstrate topographical differences of brain iron deposition between progressive supranuclear palsy (PSP) and the parkinsonian variant of multiple system atrophy (MSA-p) with SWI images.
METHODS: A total of 11 patients with PSP, 12 with MSA-p, 15 with Parkinson's disease (PD), and 20 age-matched healthy controls underwent SWI of the brain. Mean phase shift values of the red nucleus (RN), substantia nigra (SN), head of the caudate nucleus (CN), globus pallidus (GP), putamen (PUT), and thalamus (TH) were calculated and compared between groups. A voxel-based analysis of the processed SWI was performed to determine topographical differences of iron-related hypointense signals in PUT, GP, and TH.
RESULTS: Patients with PSP and MSA-p had significantly higher levels of iron deposition than control and PD groups. Comparing patients with PSP and MSA-p, differences were found in iron concentrations of the RN, SN, GP, and TH, which were higher in the PSP group. However, iron levels in the PUT were higher in the MSA group (p<0.05). The area under curve (AUC) indicated that the PUT was the most valuable nucleus in differentiating MSA-p from PSP and PD according to phase shift values (AUC=0.836). Meanwhile the GP (AUC=0.869) and TH (AUC=0.884) were the two most valuable nuclei in differentiating PSP from MSA-p and PD. Voxel-based analysis showed subregional differences in iron-related hypointense signals in the PUT, GP, and TH between MSA-p and PSP groups. Patients with MSA-p had significant increases of iron-related hypointense signals in the posterolateral PUT and adjacent lateral aspect of the GP, whereas the PSP group had increased hypodense signals in the anterior and medial aspects of the GP and TH.
CONCLUSION: Our data demonstrate that pathological iron accumulations are more prevalent and severe in PSP compared to MSA-p. The distribution of high-iron-content regions in this study reflects pathoanatomically relevant sites. This finding allows for the use of MRI-based brain iron mapping as a technique to indirectly identify pathological changes.