[Identification of ictal foci by EEG and MR apparent diffusion coefficient map in a case of human herpesvirus 6-associated encephalopathy].

We report here a 1-year-old boy with human herpesvirus 6 (HHV 6) -associated encephalopathy. On the 3rd day of fever, he had a generalized tonic seizure followed by mild disturbance of consciousness, which recovered completely the next day. Two days later, he had skin rash of exanthema subitum, and his consciousness declined frequently. EEG demonstrated rhythmic wave bursts originating from central areas bilaterally, followed by a generalized spike-and-wave complex which was associated with disturbed consciousness. We made the diagnosis of a status of complex partial seizures. Because the focal discharge on ictal EEG, MRI was performed. In the subcortical white matter of the frontal-parietal lobes, there were high signals on diffusion-weighted MRI, the apparent diffusion coefficient of which was much lower than that of normal controls. The affected areas soon disappeared with improvement of clinical symptoms. The transient MRI findings may indicate reversible cytotoxic brain edema. He showed no neurological sequelae as yet.