Brain iron deposition fingerprints in Parkinson's disease and progressive supranuclear palsy

It can be difficult to clinically distinguish between classical Parkinson's disease (PD) and progressive supranuclear palsy. Previously, there have been no biomarkers that reliably allow this distinction to be made. We report that an abnormal brain iron accumulation is a marker for ongoing neurodegeneration in both conditions, but the conditions differ with respect to the anatomical distribution of these accumulations. We analyzed quantitative T2' maps as markers of regional brain iron content from PD and progressive supranuclear palsy patients and compared them to age-matched control subjects. T2-weighted and T2*-weighted images were acquired in 30 PD patients, 12 progressive supranuclear palsy patients, and 24 control subjects at 1.5 Tesla. Mean T2' values were determined in regions-of-interest in the basal ganglia, thalamus, and white matter within each hemisphere. The main findings were shortened T2' values in the caudate nucleus, globus pallidus, and putamen in progressive supranuclear palsy compared to PD patients and controls. A stepwise linear discriminant analysis allowed progressive supranuclear palsy patients to be distinguished from PD patients and the healthy controls. All progressive supranuclear palsy patients were correctly classified. No progressive supranuclear palsy patient was classified as a healthy control, no healthy controls were incorrectly classified as having progressive supranuclear palsy, and only 6.7% of the PD patients were incorrectly classified as progressive supranuclear palsy. Regional decreases of T2' relaxation times in parts of the basal ganglia reflecting increased brain iron load in these areas are characteristic for progressive supranuclear palsy but not PD patients.