Early diagnosis of herpes simplex encephalitis in childhood. Clinical, neurophysiological and neuroradiological studies.

In the initial phase of HSE the clinical symptomatology is more variable and insidious in babies and young children than in older children and adults. Combined clinical, neurophysiological and neuroradiological studies have been carried out in 12 children with proven HSE. Ten patients had the first EEGs taken during the acute phase of the illness and all showed large amplitude irregular slow activity, sharp waves and often spikes with variable distribution; in 7 cases periodic phenomena were recognisable. At a later stage localised low amplitude EEG activities were found in children with focal neurological symptoms. Areas of low attenuation were seen in the CT scans of the 7 children who had this investigation done at an early stage of their illness. Such low density regions persisted at follow-up and eventually cerebral atrophy with irregular features became obvious. Prompt EEG investigations combined with CT scans provide an early diagnostic clue for treatment. Follow-up EEG studies (including VEP) and CT scans may help assess the severity of residual cerebral damage in the survivors.