Herpetic brainstem encephalitis.

A fatal case of brainstem encephalitis presented as an acute lateral medullary syndrome. Pathologic examination showed a focal encephalitis along the roots and the intramedullary portion of the right vagus and glossopharyngeal nerves. Herpesvirus particles were demonstrated by electronmicroscopy of formol-fixed material. This is the second known case of herpetic brainstem encephalitis confirmed by postmortem examination and the only one in which the infection was limited to the brainstem. This case and a review of previously reported cases suggest that the viral infection could proceed to the brainstem through the vagus and glossopharyngeal nerves, probably from a source of latent herpetic infection in the respective ganglia.