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 is an indirect 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.
The information provided in this site is
designed to be an educational aid only. It is not intended to
replace the advice and care of your child's physician, nor is
it intended to be used for medical diagnosis or treatment. If
you suspect that your child has a medical condition, always
consult a physician.
