Head Growth in Children

Ask Dr. Paul


DEAR DR.PAUL: My son is 18 months old and at his last couple of physicals the doctor has shown some concern about his head circumference, which is 47.5 cm. Should I be concerned about his head being too small?


PEDIATRICIAN DR.PAUL Answers: Head growth occurs at its most rapid rate during the first year of life. The head grows to almost 80 per cent of the adult size during the first year, then grows at a slower pace. Importantly, head circumference growth indirectly is a measure of brain growth. The skull of a baby is made up of several bones that are not fully joined to allow for this growth. The head circumference is taken by placing a paper or plastic measuring tape around the child's head above the forehead. Both the actual size of the head and more importantly, the rate at which it grows are important components of the routine baby check up. What can go wrong? Well, if the head is too large, or growing too quickly, or on the other hand, if the head is too small or growing too slowly, these are signs of possible problems. Having said that, in your son's situation, looking at just one value in time is difficult as we need to assess the growth pattern. This is best done by plotting the head circumference on a chart, much in the same way as the height and weight are recorded and followed at each pediatric check up. The head following a normal growth rate is the most important sign that things are normal. Also, for an 18-month-old boy the average (median) head circumference is 48.4 cm or 19.1 inches, with the normal range between 46.3-50.6 cm (18.2-19.9 inches). If the head circumference is smaller than 46.3 cm (18.2 inches), the lower limit of normal range, but the rate of growth is normal, then we think of familial microcrania...a tendency for a small head, where growth and development occur perfectly normally otherwise. In this case, a measurement of the parents' head size often shows that one of them has a small head. Actually the same is true for a larger than normal head that follows a normal pattern or growth rate: This is known as familial macrocrania or large head, that runs in the family. Again one of the parents will likely have a larger than normal head. It is important to have your baby's head circumference measured regularly. It is really the rate of growth of the head that we want to focus on, rather than the actual size itself. In this way we can screen for both the slowing down or acceleration of head growth, both of which are conditions that need prompt (in some cases urgent) investigation and attention.




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