The influence of age at onset of acute disseminated encephalomyelitis (ADEM) on cognitive, educational, and social functioning was evaluated in 19 children (10 < 5 years of age) admitted to the Royal Children’s Hospital, Melbourne, Australia. Compared to controls, stratified for age and socioeconomic status, patients who developed ADEM before 5 years of age had a lower mean intelligence quotient (p<0.01), significantly lower scores on reading and spelling (p<0.001), and a higher incidence of severe behavioral and emotional problems. The young onset group also obtained a significantly lower standard score on spelling in comparison with the old onset group (p<0.05). No significant differences were found on cognitive measures in children treated or not treated with steroids; the number not treated was too small for a meaningful conclusion. The frequency of MRI abnormalities was similar in the young and old onset groups, and the proportion of children experiencing one or more relapses was also similar. 
COMMENT. Long-term neuropsychological dysfunction may occur in children who develop ADEM in early childhood, despite the absence of persisting neurologic deficits. Children under 5 years of age recovering from ADEM should be tested for possible cognitive, behavioral, and emotional problems that require educational and psychological intervention.