[A case of SSPE that showed watershed infarction like image on MRI initially, and progressed to whole brain atrophy].

We reported a 15-year-old male patient of subacute sclerosing panencephalitis (SSPE), progressed from stage I to stage IV. On his admission, his clinical state was stage I with disturbance of generalized attention, myoclonus of upper limbs and no focal cortical signs. After rapid progression to stage III in a month, his clinical state became fairly stable and gradually advanced to stage IV. We followed him with serial CT and MR images. On imagings we found initial lesion in left parietoocipital lobe and spread in right parietoocipital lobe, anterior lobe and then brain stem, showing low density on plain CT scans and high intensity of T2 weighed MR images. This initial lesion situated in watershed area was hardly distinguishable from watershed infarction. In addition, we found blood flow decrease in vertebral artery system with SPECT and Doppler flowmetry. These findings suggested vascular pathogenesis of SSPE. We showed the imaging processes of SSPE progression from formation of initial lesion to demyelination and gliosis of total brain.