A distinctive clinical EEG profile in herpes simplex encephalitis.

Two patients with herpes simplex encephalitis had clinical courses consisting of an acute febrile illness with early onset of seizures and rapidly progressive neurologic signs evolving to coma and death within 3 weeks. The electroencephalograms of both patients were similar and showed widespread, periodic, stereotyped sharp-and-slow-wave complexes occurring bilaterally over both hemispheres, as well as transient episodes of electrographic seizure activity occurring unilaterally, with suppression of the periodic activity on that side. Although the electroencephalographic findings are not pathognomonic, when associated with an acute encephalitic process, they would suggest the diagnosis of herpes simplex encephalitis.