[Case of herpes simplex encephalitis with hypersomnia and low orexin level in the cerebrospinal fluid].

A 60-year-old woman suffered from high fever (38°C) and abnormal behavior, was admitted to our hospital on the seventh day of the fever. At admission, she was stuporous, and a cerebrospinal fluid (CSF) analysis revealed pleocytosis (55/μl, monocytes). Fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images showed high-intensity signals in the medial temporal lobe, inferior surface of the frontal cortex, right cerebellar vermis, and left thalamus. We diagnosed herpes simplex encephalitis, based on the finding of an elevated titer of herpes simplex virus antibody in the CSF (2.90). She was started on treatment with acyclovir and steroid pulse therapy, which was followed by rapid clinical improvement. After recovering from the stupor, the patient exhibited the symptoms of hypersomnia with low orexin level in the CSF. Thus, we should bear in mind that other than consciousness disturbance, patients with herpes simplex encephalitis can also present with rare complications due to the extent of the lesions.