Nigrostriatal Degeneration in Parkinson Disease: Evaluation by Diffusion Tensor Tract-Specific Analysis

Diffusion tensor tractography was used to evaluate whether diffusion metrics in the nigrostriatal pathway could diagnose Parkinson disease. Diffusion tensor imaging was performed on 30 patients with Parkinson disease and 32 healthy controls by using a 3.0 Tesla magnetic resonance imaging system. Diffusion tensor tractography was used for both groups to visualize the nigrostriatal and corticospinal tracts. The fractional anisotropy (FA) and mean diffusivity (MD) of the tracts were evaluated. Receiver operating characteristic (ROC) analysis was used to determine whether diffusion metrics of the nigrostriatal pathway could be used to diagnose Parkinson disease. Mean FA values (±SD) of the nigrostriatal tract in Parkinson disease patients (0.41 ± 0.025) were significantly lower than those in the control group (0.43 ± 0.022; p = 0.00068) and showed a sensitivity of 66.7% and specificity of 60%. There were no significant differences in the MD values of the nigrostriatal tract or the FA and MD values of the corticospinal tract between Parkinson disease patients and the control group. FA values of the nigrostriatal pathway in Parkinson disease patients were significantly lower than those in normal, healthy individuals. Reduced FA was generally thought to reflect neuronal loss, gliosis, or demyelination of nerve fibers. This result might provide a useful measure for diagnosing Parkinson disease and evaluating patients’ clinical condition.