Structural changes of the substantia nigra in Parkinson's disease as revealed by MR imaging

BACKGROUND AND PURPOSE: The possibility of using MR imaging as a sensitive marker of the structural changes in Parkinson's disease has been a long-sou ght goal. We describe a new method for imaging and quantifying the morpholo gic changes of the substantia nigra in Parkinson's disease and compare radi ologic findings with clinical evaluation. METHODS: Using a combination of two MR imaging inversion-recovery pulse seq uences, the substantia nigra was imaged in six patients with Parkinson's di sease and six age-related control participants. A radiologic index was defi ned and used to quantify the signal changes that were observed in the patie nts. The radiologic index was compared with clinical scores obtained from t he Unified Parkinson's Disease Rating Scale. RESULTS: The images showed loss of signal in a lateral-to-medial gradient i n cases of Parkinson's disease, corresponding to the known neuropathologic pattern of degeneration. The radiologic index was highly correlated with th e Unified Parkinson's Disease Rating Scale score, and there was no overlap in radiologic indices between the patient and the control groups (P < .0000 5), CONCLUSION: This study suggests that MR imaging is sensitive to structural changes in even the earliest cases of Parkinson's disease, thereby indicati ng the potential for detecting presymptomatic disease. Furthermore, a radio logic measure has been defined that correlates with the conventional clinic al measure of disease severity. Therefore, MR imaging could prove to be a s ensitive biological marker for objective staging of the disease.