Herpes simplex encephalitis during radiation therapy in a patient with nasopharyngeal carcinoma

A 37-year-old female patient was diagnosed with nasopharyngeal carcinoma (NPC) and treated with concurrent chemoradiotherapy treatment. After 27/32 fractions of radiotherapy (RT) treatment, she developed low grade fever. Over the next few days, high fever and refractory seizures developed and the patient was diagnosed with herpes simplex encephalitis (HSE) after detected positive polymerase chain reaction result in herpes simplex virus-1 of cerebrospinal fluid (CSF) and abnormal signal intensity in bilateral of the temporal lobe, insula, and frontal lobe in MRI. After 4 weeks treatment with acyclovir, the patient was partly recovery with some residual personality change. Although HSE case following brain irradiation was sporadically reported, from our knowledge, no HSE case following NPC irradiation was reported before. This finding suggests that HSE should be a part of the differential diagnosis of acute neurologic decline in NPC patients undergoing treatment.