The neuroradiological, developmental, and psychological, long-term sequelae of 41 infants (30 boys, 11 girls) diagnosed with macrocephaly (an occipito-facial head circumference [OFC] >95th centile) at a family health service visit between 1985 and 1986 were studied at the Royal Alexandra Hospital for Children and other centers in Sydney, Australia. After initial presentation at a mean age of 8 months (range 3-30 months), all participants received CT or MRI of the head and neurologic examinations at a mean age of 3 years (range 9-87 months). Fifteen of the original 41 patients who gave consent were re-examined at a mean age of 18 years (range 17-20 years). Neurologic exams were normal initially and at follow-up, and OFCs had normalized, relative to adult growth charts, and were proportionate to heights for boys or girls. MRI images re-evaluated in 9 participants showed regression of orbito-frontal extradural collections and a normal or slightly enlarged ventricular space compared to infant examinations in all except one. None had developed an increase in intracranial pressure. Clinical interviews in 15 participants revealed half with reading or arithmetic difficulty in school, 2 had motor delay, and 2 were speech delayed. Neuropsychological testing in 9 showed that 6 had normal intellectual ability and 3 were in the low average to borderline range; 3 had attention problems, and 6 had a high rate of omission and/or commission errors. 
COMMENT. Previous follow-up studies of infants with idiopathic macrocephaly have shown variable results regarding neurological, radiological and psychological outcome, some showing normalization of the head circumference within 18-24 months, and some with persistence of radiological abnormalities in the long-term. The present study shows in a small number of macrocephalic infants followed to young adulthood, an initial orbito-frontal collection of extradural fluid and enlarged subarachnoid space will regress and normalize, in the absence of a co-existing developmental disorder or hydrocephalus. Idiopathic macrocephaly may be considered a normal variant, radiologically, but neuropsychologically, individual variations can be expected, with impairments in visuo-motor skills and attention. Early investigation of cognitive function, and monitoring of behavioral and academic performance may be indicated in infants diagnosed with idiopathic macrocephaly.