Structural Changes of the Substantia Nigra in Parkinson's Disease as Revealed by MR Imaging

Upper row displays an example of axial WMS and GMS MR acquisition images of the mesencephalon in a control participant. The cerebral peduncle (second row, left) extracted from the WMS midbrain image serves as a template to extract the GMS image of the cerebral peduncle shown on the right. The SN_C is seen as a bright arch in the peduncular WMS image, whereas it appears as a dark band in the corresponding GMS image. Note also the substantia nigra pars reticulata (SN_R) reaching across the crus cerebri toward the SN_C. The ratio image (WMS/GMS) of the two images in the second row yields the color-coded ratio image displayed on the bottom. All black and white images are shown using a standard display of 256 gray levels. The color image uses a 256-pseudocolor lookup table.fig 2. Ratio images of the cerebral peduncle displayed in pseudocolors show the morphologic characteristics of the SN_C in two control participants (C1 and C2) and the structural changes in two patients with Parkinson's disease (P1 and P2). The substantia nigra pars reticulata (SN_R) is indicated for participant C1. Notice that the SN_C in control participants reaches out toward the peduncular edge in the upper section, taking on the form of an arch. In the images of patient P1, who has Parkinson's disease, thinning and loss of signal can be seen in the lateral segment of the SN_C in the upper section. The lower section shows islands of cell loss on both sides of the SN_C. Note the considerable thinning and loss of signal in both upper and lower sections of the images of patient P2, who has late-stage Parkinson's disease. Left and right sides show two rims of preserved signal