The electroencephalogram (EEG) is a noninvasive test that is easily accepted by the family and the child, and is valuable in the diagnosis of viral encephalitis. In viral encephalitis, the EEG abnormality rate can be more than 90%, mainly manifesting as diffuse abnormal slow activity background.
However, it should be noted that: 1. The EEG changes in viral encephalitis are nonspecific and the diagnostic value of the EEG should never be overemphasized. A normal EEG does not exclude viral encephalitis; an abnormal EEG does not confirm the diagnosis of viral encephalitis. Some pediatricians in some areas make the diagnosis of “viral encephalitis” based only on the presence of headache or other non-specific symptoms in the child, plus the presence of “mild abnormalities” in the EEG, which is incorrect.
The degree of EEG abnormality in viral encephalitis is not always consistent with the actual severity of the lesion; recovery from abnormal EEG in viral encephalitis is slower than clinical recovery, often taking weeks or months; individual EEGs in viral encephalitis show epileptiform discharges during recovery, but if clinical seizures do not occur, the diagnosis of epilepsy cannot be made on the basis of EEG alone, or even with the addition of antiepileptic drugs.