Unusual progression of herpes simplex encephalitis with basal ganglia and extensive white matter involvement.

We report a 51-year old male with herpes simplex encephalitis (HSE) showing unusual progression and magnetic resonance (MR) findings. The initial neurological manifestation of intractable focal seizure with low-grade fever persisted for three days, and rapidly coma, myoclonic status, and respiratory failure with high-grade fever emerged thereafter. The polymerase chain reaction (PCR) result of cerebrospinal fluid (CSF) was positive for HSV-1 DNA. In the early stage, MR images (MRI) were normal. On subsequent MR diffusion-weighted (DW) and fluid-attenuated inversion recovery (FLAIR) images, high-intensity areas first appeared in the left frontal cortex, which was purely extra-temporal involvement, and extended into the basal ganglia, then the white matter, which are relatively spared in HSE. Antiviral therapy and immunosuppressive therapy did not suppress the progression of HSE, and finally severe cerebral edema developed into cerebral herniation, which required emergency decompressive craniectomy. Histological examination of a biopsy specimen of the white matter detected perivascular infiltration and destruction of basic structure, which confirmed non specific inflammatory change without obvious edema or demyelination. The present case shows both MR and pathological findings in the white matter in the acute stage of HSE.