Letter to the editor: Herpes encephalitis

[Reactivation of latent viruses in Neurology]

After establishing latent infection, some viruses can be reactivated by the alteration of host immunological conditions. First, we reviewed viruses that can cause neuronal damage by reactivation. Then we focused on the herpes simplex virus (HSV). The reactivation leads to neuronal damages through two possible mechanisms; "reactivation of a latent herpes virus" by which viruses can cause direct virus neurotoxicity, and "post-infectious immune inflammatory response" by which a focal reactivation of HSV leads to an inflammatory reaction. The former is radiologically characterized by cortical lesions, the latter is characterized by subcortical white matter lesions. We experienced a female, who underwent the right posterior quadrantectomy and then developed recurrent herpes encephalitis caused by herpes simplex reactivation, which pathologically demonstrated inflammation in the white matter, suggesting a post-infectious immune inflammatory response. The patient was successfully treated with immunosuppressants. The reactivation of the HSV is extremely rare in Japan. Neurologists should recognize this condition because this disorder will increase as epilepsy surgery gains more popularity.

Herpes simplex reactivation following neurosurgery: case report and review of the literature

Herpes simplex encephalitis is a common viral encephalitis associated with significant morbidity and mortality if not diagnosed and treated early. Neurosurgery may be an impetus for viral reactivation, either from direct nerve manipulation or high-dose steroids often administered during cases. The authors present the 40th known case of herpes simplex virus (HSV) encephalitis following neurosurgical intervention and review the previously reported cases. In their review, the authors observed positive HSV polymerase chain reaction (PCR), which had initially been negative in several cases. In cases in which there is high suspicion of HSV, it may be prudent to continue antiviral therapy and retest CSF for HSV PCR. Antiviral therapy significantly reduces mortality associated with HSV encephalitis.