Evaluating craniosynostosis

A baby's skull must grow quickly to accommodate a rapidly growing brain. Normally, the baby's skull grows perpendicular to each of the cranial sutures, and the sutures must be open to allow for this growth. Normally, the sutures fuse (e.g., close) by two years of age.

If a suture fuses early, the baby's head can end up markedly misshapen. This process of early fusion is known as craniosynostosis (or synostosis for short).

With craniosynostosis, the skull growth that normally occurs perpendicular to the fused suture is inhibited which causes the skull to grow and expand in other directions. If several sutures fuse early, the overall skull growth is significantly restricted and brain injury can occur. Early suture closure is relatively rare and occurs in only 1 of 2 000 births.

The diagnosis of craniosynostosis has been somewhat confounded by another phenomenon. Over the past couple of decades, pediatric specialists have recommended that infants sleep on their backs, whereas they used to recommend placement on the abdomen for sleep. Back sleeping is thought to decrease the incidence of sudden infant death syndrome (SIDS).

Increased back sleeping in infants has resulted in a common phenomenon of positional skull remodeling where the back of the skull becomes flattened. This is known as positional plagiocephaly or positional occipital molding. In this situation, the entire back or one side of the head may be flattened if the baby rests preferentially on one side. This is often mistaken for true craniosynostosis; however, no sutures have fused early and the skull is just misshapen.

Positional plagiocephaly has no effect on brain development. It can often be remedied by time or simple changes in the baby’s positioning. On the other hand, true craniosynostosis may require surgery to correct.

Obtain a perinatal history

When evaluating an infant for craniosynostosis, obtain a thorough perinatal history. Look for obvious craniofacial deformities in the child’s parents and ask about familial syndromes. Sometimes, you can see a craniofacial deformity run right through a family. In this situation, the infant may need a referral for genetic testing.

Most importantly, access the child’s head circumference growth chart. Start one yourself if it has not been kept on file.

Perform a general physical and neurological exam

Look at the child from the front, side, and (most importantly) above; note any abnormalities in the skull shape. Sometimes, you’ll have to dangle keys or something interesting in front of the child to get a good look from above.

Next, palpate the child’s head. In most cases of synostosis, the affected sutures will be overlapping, heaped up, readily palpable, and immobile. In a young baby, if the bones on either side of the affected suture are ballotable (meaning that they move up and down with applied pressure), the suture is unlikely to be fused.

After checking the sutures, measure the child’s head circumference. Generally, craniosynostosis only affects one suture and overall head growth is not inhibited. Only multisuture synostosis is associated with inadequate head growth, and these children will have remarkably abnormal head shapes.

A child whose head growth curve is below the average head circumference growth curve (and has a normally shaped head) is very unlikely to have multisuture or pan-suture synostosis. Rather, they may have parents with small heads, or (rarely) they could have one of a series of rare developmental disorders.

Finally, perform a thorough neurological exam. Assess the baby for any signs of associated developmental delay or focal deficits. If any are present, refer right away to a pediatric neurologist or a developmental pediatrician.

Order diagnostic imaging

Some synostoses can be associated with hydrocephalus. These children will usually have facial deformities as well, and the craniosynostosis is part of an overall genetic syndrome. If the child’s head circumference is crossing growth chart percentile lines, schedule brain imaging to rule out hydrocephalus.

Watch for signs of increased intracranial pressure

Keep in mind that single suture synostosis rarely causes cerebral functional deficiencies as long as the head expands along normal growth curves as the brain grows. In rare cases, increased intracranial pressure may occur alongside the usual associated signs (including headache, irritability, nausea, vomiting, lethargy, and sunset eyes).

Reassure the parents of a child with an oddly shaped head that as long as the child’s head grows normally, there will be no impact on intellectual development.

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