Microcephaly

contributed by William R. Boydston, M.D., Ph.D.
Just as with macrocephaly, microcephaly is a statistical concept and there will be normal infants and children with head circumferences below the second percentile. The most common cause of pathologic microcephaly is inadequate brain growth. As the major impetus for skull growth is brain growth, if the brain is injured during its early development (rubella, CMV, in utero stroke), the result will be a small head. The only treatment for most of these conditions is prevention.

Pediatric neurosurgeons are frequently asked to evaluate children with small heads to rule out craniosynostosis. Early closure of the sutures of the skull can certainly cause microcephaly and its early diagnosis would be imperative to allow normal brain development. The most common presentation of synostosis is an abnormal head shape, not size. Certainly in single suture synostosis the compensatory growth that occurs through the open sutures allows for continued head growth. Even with multiple suture synostosis the head is usually misshapen as excessive growth occurs via one or two open sutures. Symmetric pancranlosynostosis, which would result in a small and normally shaped head, is exceedingly rare.

There are situations where the distinction between multiple suture synostosis and small head secondary to inadequate brain growth cannot be made by examination alone. In these cases, thin cut CT scans angled perpendicular to the coronal sutures show the sutures clearly and allows determination of their patency. In addition the brain is visualized to rule out a parenchymal abnormality.