Cerebrospinal fluid dynamics in megalencephaly.

Macrocephaly is one of the signs most commonly used in the diagnosis of hydrocephalus. Two children are reported who presented with macrocephaly. The results of neurological examination were normal apart from delay in mental development. Head circumferences were above the 98th percentile. Air studies showed mildly dilated ventricles with no obstruction, and ventriculolumbar perfusions indicated normal rates of cerebrospinal fluid formation and absorption. At seven years of age the children were mildly mentally retarded, with head circumferences above the 98th percentile. In the girl the ventricles were still mildly dilated but in the boy they were normal. It is concluded that the macrocephaly in these two children was the result of progressive megalencephaly and not of abnormal ventricular enlargement (hydrocephalus).