Herpes simplex virus encephalitis is the more common type of non-epidemic encephalitis, accounting for approximately 2% to 19% of diseased brains and 20% to 75% of sporadic necrotizing encephalitis . The clinical manifestations are acute onset with high fever, headache, vomiting, myoclonus and seizures, mostly accompanied by impaired consciousness, with severe cases rapidly entering deep coma. Some of the first symptoms are confusion, dull expression, reduced speech and movement, unresponsiveness or restlessness, incoherent speech, memory impairment, disorientation, and even delusion, hallucination, delusion and bizarre behavior, and delirium. Yang Jie, Department of Pediatric Internal Medicine, Qilu Hospital, Shandong University Some children have herpes on the lips and mouth. The neurological symptoms are diverse, with common cases including hemiparesis, aphasia, simultaneous deviation of both eyes, involuntary movements, some with decerebrate or decorticate state, optic papillar edema, cervical tonicity, positive meningeal stimulation sign, lid ptosis, pupil size inequality. The clinical presentation of herpes simplex virus encephalitis is similar to that of other diseased brains, but recurrent convulsive episodes early in the disease and focal signs suggestive of temporal or frontal lobe lesions are strongly suggestive of a herpes simplex virus as the cause. Ancillary tests may reveal increased cerebrospinal fluid pressure, increased white blood cell count and protein, mainly lymphocytes, and normal sugar and chloride. EEG reveals diffuse high-amplitude slow waves, more pronounced in the temporal region, and periodic high-amplitude spikes. MRI detects inflammation at the base of the frontal lobe and medial temporal lobe earlier than EEG, CT or radionuclide brain scan and helps to start antiviral therapy as soon as possible before neurological symptoms worsen. Polymerase chain reaction (PCR) techniques can detect specific DNA of herpes simplex virus in the cerebrospinal fluid, which is rarely isolated from the cerebrospinal fluid. A comparative test of double sera can help with the diagnosis. Although there is a tendency for herpes simplex virus IgG to rise during the first 10 to 12 d of disease, this test is not helpful in the acute phase for diagnosis.