Researchers at the Astrid Lindgren Children’s Hospital and Karolinska Institute, Stockholm, Sweden, reviewed medical records of 71 of 93 children who were treated for acute encephalitis at 5 weeks to 17 years of age in 2000-2004, using questionnaires and a structured telephone interview conducted with the parents. Fifteen children with the most severe symptoms at time of discharge underwent EEG and tests of reaction time and working memory. Mean age at onset of encephalitis was 6.7 y (range 0-17) and time to follow-up evaluation was 5.4 y (range 3-8). Males outnumbered females 47 to 24 or 2:1. The cause was known in 37 (52%). Persisting symptoms were reported in 25 (60%) of 42 children >5 y of age and in 13 (45%) of 29 children <5 y of age. Symptoms resolved completely in 24 (34%) of 71 children (within 6 months in 21 children and by 1 year in 3). Residual symptoms were reported in 17 (40%) of 42 children >5 y of age and in 8 (28%) of 29 children <5 y of age at time of acute illness. The most common residual symptoms in the older group were personality changes, poor memory, noise sensitivity, and poor concentration, and poor concentration and feelings of frustration in the <5 y group. A confirmed/probable microbial cause was established in 52% of the children. Prevalence of persisting symptoms was similar in cases of known and unknown cause, and all agents were equally causative of persisting symptoms, even those considered benign. Factors indicative of a poor prognosis and persisting symptoms at follow-up included admission to ICU in acute phase, and fever, seizures, EEG abnormalities, and moderate/severe symptoms at discharge. Postencephalitic epilepsy developed in 7 (10%) children. Girls had a fivefold increased risk of epilepsy compared with boys (P<0.05). Children with seizures during the acute illness had an eight-fold increased risk of epilepsy (P<0.05). All children who developed epilepsy had abnormal EEG findings during acute encephalitis, and recordings were abnormal in 9 of 15 with repeat EEGs at follow-up. Cognitive testing showed better results with increasing age for reaction time but not for working memory. Children with encephalitis had slower reaction times than controls. [1]

COMMENT. Recovery from acute encephalitis in children is incomplete in 66% and complete in 34% cases at long-term follow-up. Many of those considered fully recovered at discharge have persisting symptoms later. Those who recover completely do so within 1 year. Ten percent develop post-encephalitic epilepsy, and girls are especially vulnerable. In addition to EEG abnormalities, neurological and MRI findings at time of acute illness are predictive of outcome. (Lee WT et al. Eur J Ped Neur 2007; 11(5):302-309)[2]