Does your kiddo have a huge noggin’, or know someone’s kid who does? While most of the time it’s just genetic and nothing to worry about, there are times that it can be a sign of a bigger problem. Macrocephaly is the medical term for a disproportionately large head. To be precise, a child is labeled as having macrocephaly if the measurement around the head (called a head circumference) is more than 2 standard deviations above the mean (roughly the 97%) for age and gender.  Sometimes you’ll hear the phrase “OFC” which stands for occipitofrontal circucumference, which is just another term for head circumference. It’s worth mentioning that doctors never look at a number in complete isolation. If I have a huge kid (95% for height and weight), then I’m not likely to worry about a head that measures at 97% because it isn’t disproportionate. I may worry about a 75% size head, though, if the child is tiny (5% for weight and height).

What can cause macrocephaly?

1. Genetics: By far, most cases of macrocephaly are genetic. Usually in genetic cases, one of the parents and often times the siblings will also have big heads. Usually when I ask if there are big heads in the family, mom will smile and laugh saying, ‘oh yeah, all the Smiths’ have big heads.’ This is generally very reassuring. Think of it like genetically tall people. When there are really tall genes in the family, everyone tends to be tall.
2. Hydrocephalus: This is when the body creates extra fluid around the brain. Usually there is really thin layer of fluid between the brain and skull. If the body makes too much, it will push the skull out and grow the head. To treat this condition, a shunt or drain is usually placed.
3. Space-Occupying Lesion (like a tumor): Tumors usually have to be pretty big to make the head grow disproportionately. Additionally, when a tumor (or the like) is the cause of the big head, there are usually other worrying signs to go with it (regression of milestones—like a child not being able to walk who once could, or headaches).
4. Enlarged/Malformed brain: Typically these cases are picked up prenatally. If the brain isn’t forming properly, often an ultrasound will detect it.
5. Syndromes: There are a few genetic syndromes that are associated with big heads (e.g., NF-1, Sotos syndrome, Beckwith-Wiedemann). Typically in these cases, your child will have other physical symptoms that would lend to that diagnosis.
6. Other rare causes: A list is never exhaustive, so this is where I would include the random, rare causes.

What’s a normal size?

When a baby is born, most heads measure about 35 cm (normal range: 32-38 cm). An infant’s head grows the fastest in the first 4 months of life. By 1 month of age, most infants’ heads have grown 3 cm to 38 cm. The American Academy of Pediatrics recommends doctors measure a child’s head circumference at every well child check until the age of 2. The Centers for Disease Control & Prevention recommend measurements be taken until 3 years old. These first few years are the most important time to measure because the brain growth is maximal at this time in life.

When should I worry?

If your child has a big head AND:

1. NO family history of big heads.
2. If the head is growing much faster than the other body measurements (height and weight).
3. If you’re child has a loss of milestones (as mentioned above, like no longer talking or walking when he/she could do it previously).
4. Your child is born with other physical abnormalities (which might suggest a syndrome or genetic problem).
5. Your child is old enough to start complaining of other head-related symptoms (e.g., headache, visual changes)
6. The shape of the head is unusual (indicating perhaps that the sutures are closing prematurely or in the wrong order).
7. Your parent instinct tells you there is something wrong. (I always like to add this one, because sometimes parents just know when something is wrong even when there isn’t scientific evidence.)

What should I do?

1. Talk to your pediatrician about it. (Chances are it will be your pediatrician who picks up the problem in the first place).
2. Decide on an action plan.
   1. Watchful waiting may be the best approach in some circumstances (especially if genetically big heads are suspected).
   2. Imaging may be more appropriate in other circumstances (essentially everything else).
      1. A head ultrasound (while not the most accurate) is often a first step. It is relatively easy, inexpensive, and doesn’t require sedation. The limitation is that the anterior fontanelle (the little soft spot on the front/top of the head) has to be open and big enough for an ultrasound probe (so it’s only good in the really young, like sub 6 months).
      2. MRI is the most definitive and sensitive to detecting problems. The reason, docs don’t jump to them is that MRIs are expensive, time-consuming, and require sedating young children (which has a risk to it). There is no radiation with an MRI.
      3. CT scans are quick and easy to obtain, but have lots of radiation (a definite risk). They are most appropriate in the acute (or short-term) stage. That is, if the head has rapidly changed size (e.g., concern for a bleed in the head).
   3. Referral to a specialist (e.g., a neurology or genetics). If your child has other symptoms that are suggestive of problems like genetic syndromes, your doc may refer you to a specialist.

Never feel bad about bringing up a concern with your doctor. If you think your child’s head is big, bring it up with your doctor. If nothing else, the peace of mind is well worth the trouble.