Herpes simplex encephalitis presenting with exclusively frontal lobe involvement.

The authors report a patient with herpes simplex encephalitis who presented with magnetic resonance imaging (MRI) lesions exclusively in the frontal lobes, including the bilateral anterior cingulate gyri. She is making a good recovery after therapy with intravenous acyclovir. A similar presentation with a fatal outcome was previously reported by Rose et al (Neurology 42: 1809-1812, 1992). MRI shows temporal lesions in most patients with herpes simplex encephalitis, whereas occasional patients have normal imaging. A high index of suspicion for the diagnosis of herpes simplex encephalitis should be maintained when a patient presents with fever and brain lesions involving extratemporal limbic system structures.