Herpetic encephalitis with autoimmune recurrence following cerebral aneurysm clipping

A man in his late 60s with well-controlled HIV underwent an uneventful surgical clipping of an unruptured intracranial aneurism. Postoperatively, he developed fever, seizures and an altered mental status. Cerebrospinal fluid (CSF) showed lymphocytic pleocytosis, high protein count and a positive herpes simplex virus (HSV)-2 PCR. Acyclovir was started. Brain MRI showed right hemisphere T2/FLAIR-weighted anterior temporal cortical and subcortical hyperintensities. After 2 months, he developed psychosis, an upper limb tremor and pyramidal tract dysfunction. A new brain MRI revealed a new right frontal white matter lesion, extending to the corpus callosum. Anti-N-methyl-D-aspartate receptor (NMDAR) antibodies were positive in CSF, while there was no evidence of active HSV infection. Methylprednisolone and IVIg were started, and a significant clinical improvement was achieved.If an unknown inflammatory process occurs after surgery, herpetic encephalitis should be considered, and treatment should be initiated precociously. Since herpetic encephalitis can trigger an anti-NMDAR encephalitis, this autoimmune complication must be considered.