MR findings in neonatal herpes simplex encephalitis type II.

The CT findings in neonatal herpes simplex encephalitis (HSE) type II have been previously described, whereas magnetic resonance (MR) findings as yet have not. Early CT findings can be subtle and difficult to detect. However, as the abnormalities evolve, most notably the strikingly increased density of cortical gray matter, they appear highly characteristic of neonatal HSE type II. This case report with neuropathologic verification describes serial MR and CT findings in HSE type II that suggest an etiology of the increased density characteristically seen on CT scans; it does not appear to be hemorrhage or calcification.