Herpes simplex encephalitis

A 76-year-old woman with a history of hypertension but without dementia presented to the emergency room due to episodes of confusion during a neighbour’s visit. Upon arrival, she had a temperature of 38.4 °C, a heart rate of 103/minute, and a blood pressure of 163/91 mmHg. Physical examination revealed cognitive impairment, including difficulty recalling personal information and aphasia. Magnetic resonance imaging (MRI) findings showed hyperintensity in the temporal lobe on diffusion-weighted imaging (Fig. 1) and fluid attenuated inversion recovery sequences (Fig. 2). Her cerebrospinal fluid (CSF) analysis revealed glucose level of 66 mg/dl (range, 50 to 80 mg/dl), protein level of 119 mg/dl (reference range, 15 to 45 mg/dl), and cell count of 12 cells/μl (reference range, 0–5 cells/μl), with 90% mononuclear cells. With a suspicion of herpes simplex encephalitis, the patient was given intravenous acyclovir (30 mg/kg per day) and steroid pulse therapy. Subsequent CSF polymerase chain reaction (PCR) confirmed herpes simplex virus type 1 encephalitis. Following completion of a 21-day course of acyclovir, CSF PCR analysis revealed clearance of the virus. However, persistent memory impairment, disorientation, and hyper cortical sensory aphasia led to her transfer to a rehabilitation facility 8 weeks after her admission.

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FIG 1.

Diffusion-weighted magnetic resonance imaging showed high signal intensity in the left temporal lobe

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FIG 2.

Fluid-attenuated inversion recovery sequences showed high signal intensity in the left temporal lobe

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Typically, herpes simplex encephalitis manifests with symptoms such as headache and fever, progressing to seizures, cognitive impairment, behavioural changes, and focal neurological signs. Cognitive impairment can be mistaken for stroke, seizures for primary epilepsy, and behavioural changes for psychiatric disorders.¹ This patient highlights the importance of prompt diagnosis with MRI and CSF analysis.