Magnetic resonance imaging of herpes simplex encephalitis.

Eight brain magnetic resonance imagings (MRIs) and one spinal MRI of 7 small infants and children with herpes simplex encephalitis (HSE) were retrospectively studied. Hypointense and hyperintense areas of gray and white matters on T1- and T2- weighted images, respectively, were commonly present, with temporal lobes being the most common lesion sites. Hemorrhagic lesions were found in 4 patients (57%). Early involvement of the white matter, as early as day 4, was a common MRI finding in these patients. One patient had relapsed encephalomyelitis, whose spinal MRI showed diffuse hyperintense T2 signals from the lumbar spinal cord to the conus medullaris. All patients but one survived with major neurological sequelae. Our results indicate that MRI is a sensitive diagnostic modality in cases of HSE, and early involvement of white matter is not an uncommon MRI finding of HSE. Spinal MRI may be helpful in the diagnosis of relapsed herpes encephalomyelitis.