AN ODD SHAPED HEAD

Colin almost certainly has positional (deformational) plagiocephaly. This occurs when asymmetrical pressure on the developing occiput or skull base results in oblique flattening of the posterior skull. Causes include an asymmetrical sleeping position, torticollis and cervical spine abnormalities. There may be an underlying reason why the child sleeps in an asymmetrical position, such as a neuromuscular disorder. The typical history of positional plagiocephaly is that the baby either is born with or develops an abnormal head shape sometime after birth, which then improves with time. If the child is born with the abnormality, the deformation is due to compression in utero. As mobility increases, the likelihood of persistent asymmetrical pressure decreases, and in most cases head shape will return to normal. The major differential diagnosis is craniosynostosis. The incidence of positional posterior plagiocephaly increased markedly following campaigns to encourage infants to sleep on their back to reduce the risk of sudden infant death. Craniosynostosis is premature fusion of one or more sutures of the skull, resulting in an abnormal skull shape. The deformity is often present at birth, is progressive and does not improve spontaneously. It can result in raised intracranial pressure and developmental delay. The head shape depends on the involved suture(s). For example, sagittal synostosis results in a narrow head with an enlarged anteroposterior dimension, while lambdoid synostosis results in occipital plagiocephaly. Superficially, the head shape in lambdoid synostosis may be thought to be similar to that in positional plagiocephaly, but in fact there are important differences in the way the structure of the skull and face change, which can be used to make a diagnosis. In positional plagiocephaly, the fontanelle retains a diamond shape. Looking down on the top of the head, the head shape is a parallelogram in positional plagiocephaly, produced by unilateral flattening of the occipital area with ipsilateral bossing of the frontal and parietal bones. In lambdoid synostosis, there is unilateral flattening of the occiput but less frontal asymmetry, resulting in a rhomboid head shape. In positional plagiocephaly, the ear ipsilateral to the flattened occiput is displaced anteriorly, while in lambdoid synostosis it is displaced posteriorly and inferiorly. In craniosynostosis, a ridge is often palpable in the area of the fused suture. Where doubt remains, a skull X-ray or CT scan can be used to further assess the sutures and craniofacial structure. Sometimes craniosynostosis is part of a syndrome such as Apert’s or Crouzon’s syndrome, where the associated facial and other abnormalities usually make the diagnosis obvious. It is likely that Colin’s head shape will improve spontaneously, and even if it does not completely return to normal, hair growth will disguise much of the abnormal appearance. If the problem is severe or continues to worsen then treatment may be indicated. Helmet moulding may have some benefit by rebalancing growth of the skull. In the most severe cases, surgical intervention is sometimes warranted.

KEY POINTS

• Positional posterior plagiocephaly is the most common cause of abnormal head shape.

• Craniosynostosis usually causes progressive deformation with a ridge palpable over the fused suture(s)

. • Positional plagiocephaly usually improves spontaneously