Intracranial spaces in childhood macrocephaly: comparison of length measurements and volume calculations.

CT scanning was done to calculate the volume of intracranial spaces in children with the purpose of developing a reliable method of differentiating the various causes of macrocephaly. The technique has been applied to the CT scans of 60 apparently normal children, and the resulting graphs show the normal relationship between intracranial volumes and age from birth to 15 years. The measurements for 25 children with macrocephaly and normal rate of growth of head circumference were then compared with the reference values. It was possible to make accurate differentiations between megalencephaly, extraventricular hydrocephalus and communicating hydrocephalus. The advantage of this technique in relation to length measurements on CT scans is discussed. The authors advocate the estimation of the product of head circumference and head height as a much more reliable indication of normal and deviant head-size than head circumference alone.