Subacute sclerosing panencephalitis (SSPE) is a neurodegenerative disorder caused by persistent measles infection. Here, we report two neurologically handicapped cases presenting with atypical features of SSPE. Patient 1 who had mild mental retardation manifested acute encephalopathy with partial seizures and hemiplegia, mimicking encephalitis. He showed a fulminant course without myoclonia or a periodic electroencephalogram complex. Although SSPE is usually associated with an increased diffusion pattern, diffusion-weighted imaging of our patient showed decreased diffusion in the right hippocampus. Patient 2 with infantile hemiparesis presented with secondary generalized seizures, followed by asymettrical myoclonias involving the side contralateral to the hemiparesis. A periodic electroencephalogram complex was absent on the previously damaged brain regions. Our findings show that preexisting neurological disorders may modify the clinical or electrophysiological findings of SSPE, leading to atypical presentations. SSPE should be considered in the differential diagnosis of acute encephalopathy with lateralizing signs or unidentified seizures. Decreased diffusion resolution in diffusion-weighted-imaging may correlate with rapid clinical progression in SSPE.