INCREASED IRON-RELATED MRI CONTRAST IN THE SUBSTANTIA-NIGRA IN PARKINSONS-DISEASE

Elevated iron levels in the substantia nigra (SN) of the brain in Parkinson's disease (PD) may mediate lipid peroxidative reactions, promoting SN neuronal death. To assess SN iron accumulation in living PD patients and its relation to motor performance, we measured, in 13 nondemented PD patients and 10 normal control subjects, simple reaction time (SRT) and simple movement time (SMT), followed by head MRI in a 3-tesla system, We measured T-2 and T-2* in the right and left SN of all subjects and calculated R(2)', the relaxation rate due to local magnetic field inhomogeneities, from these values. Asymmetries of 1/T-2 (R(2)), 1/T-2* (R(2)*), or R(2)' versus asymmetries of SRT and SMT were assessed in eight PD subjects who had not taken anti-PD medication(s) for 12 hours. The average of right and left SN values for R(2) was lower, and R(2)* and R(2)' were higher, in PD patients than in controls (R(2), p = 0.046; R(2)*, p = 0.001; R(2)', p < 0.001). R(2)' best predicted group differences. The asymmetry of SRT performance was highly correlated with asymmetries of SN R(2)* (0.91; p = 0.001) and R(2)' (0.72; p = 0.03). These results strongly suggest that the increases in iron levels seen postmortem in the SN in PD are reflected in increased iron-related MRI contrast at 3 tesla in living PD patients. Correlations with motor performance in PD suggest that the clinical severity of PD may be related to SN iron accumulation.