T₂ weighted MRI image (left) shows a small, ill-defined signal in the left genu of the corpus callosum (arrowhead). Maximum velocity (VMax) of LACA was 225 cm/sec and LMCA was 252 cm/sec by transcranial doppler. On FDG (metabolic) and ([¹⁵O] H₂O) (perfusion) PET imaging (middle and right upper panels), diffuse hypoperfusion and hypometabolism is demonstrated with multifocal lesions throughout the left cerebral hemisphere. After institution of a hypertransfusion program, repeat PET scans performed at 6 months showed generalized subtle perfusion improvement (middle and right lower panels) with residual low perfusion in left occipital and parietal lobes (arrowheads). There was concurrent normalization of left frontal lobe on FDG PET.