(A) Histogram of average apparent diffusion constant (D_av) of patient 1 (bold line) and the 20 normal control subjects over all voxels in the brain. The histogram of the patient shows an enlarged compartment of CSF as compared with normal subjects. (B) Same as A for the FA. The patient’s histogram lacks large FA values, characteristic for overall white matter degeneration. (C and D) Comparison of histograms of patient 1 for the first (solid lines) and second scan 18 months later (dotted lines). (E and F) Same as A and B for the second patient. (G and H) Histograms of D_av and FA of a normal control subject who was scanned 3 times within a week (solid lines) and then once 17 months later (dashed lines). (I) FA versus D_av for patient 1 (open circle, first scan; open square, second scan) and the 20 normal control subjects (closed circles) for an ROI in the medial corpus callosum, showing pronounced white matter atrophy in the patient’s brain. Bars indicate standard deviations over the ROI. (J) FA-c diagram of the MPO region of patient 1 (open circle, first scan; open square, second scan) and 20 normal control subjects (closed circles). c quantifies the right-left component of the main diffusion direction whereas FA quantifies the overall anisotropy. The closed square marks the control subject referred to in Figure 1E. Bars indicate mean standard deviations over ROI as measured by 3 of the authors. (K) Same as J but for the inferior part of the vermis. Bars indicate standard deviations over the ROI.