Practical Evaluation of Children With Macrocephaly

The assessment of growth in general and more particularly the measurement of the head circumference is an integral part of the pediatric neurological examination. Obviously measurements of head circumference (HC) over time are more informative and should be plotted to the appropriate chart for sex and conceptional age. Macrocephaly (MC) defined as head circumference that is more than two standard deviations above the mean for age, sex, and body size, established by use of measurements and standard growth charts. Accelerated head circumference growth by more than one standard deviation from the child's previous standing can also indicate MC. Macrocephaly may be due to megalencephaly (true enlargement of the brain parenchyma) or due to other conditions such as hydrocephalus or cranial hyperostosis. Evaluation of head growth rate (ie, serial head circumferences) along with assessment of developmental milestones, perinatal history, and signs of increased intra cranial pressure (ICP) is important for differential diagnosis, urgency of imaging, and radiological interpretation. It is therefore essential to measure the HC of the parents before considering further investigations. Macrocephaly with normal growth rate and normal neurological examination is reassuring and is characteristic of benign megalencephaly, which is usually familial. Macrocephaly and accelerated head growth without elevated pressure and with normal neurological exam may occur as non progressive subarachnoid space dilatation with or without ventricular enlargement. This pattern is most commonly referred as "benign extracerebral collection of infancy" (BECC), but has also been termed as "benign enlargement of the sub-arachnoid spaces", "benign infantile HC", and "benign external HC". Macrocephaly with accelerated head growth due to progressive HC is usually associated with signs of ICP and often with declining milestones. If the cause is hydrocephalus referral to neurosurgery will be necessary. If other causes are suspected then a basic metabolic screening along with baseline biochemistry tests (such as urine organic acids analysis and blood acylcarnitine profile, studies for storage disorder like Tay-Sachs disease, specific diagnostic testing such as enzyme or gene analysis) and possible referral to a clinical geneticist will be required.