The fulminating form of subacute sclerosing panencephalitis is an extremely rare condition. Imaging findings are usually not correlated with clinical staging. We describe a 4-year-old girl with severe neuronal loss, demyelination, and gliosis in subcortical white matter by magnetic resonance spectroscopic examination even though she was diagnosed as clinical stage II. In 2 months' time, her clinical status worsened significantly. Follow-up magnetic resonance spectroscopy revealed findings that were consistent with clinical status. It is our opinion that magnetic resonance spectroscopy could demonstrate a rapidly progressive fulminating course of subacute sclerosing panencephalitis even in the early clinical stages.