There are two lambdoid sutures at the back of the skull. Occasionally one lambdoid suture may fuse prematurely causing deformity of the skull or posterior plagiocephaly. This must be distinguished from deformational plagiocephaly caused when flatness occurs from a child laying flat in one position too long. The incidence or occurrence of lambdoid craniosynostosis is the rarest form of synostosis occurring about one in 50,000 births. It only accounts for about 2-4% of synostosis cases.
Lambdoid craniosynostosis is defined by several physical findings:
- Contra-lateral skull budging – the side opposite the skull flatness grows out laterally to the side to compensate for restricted growth at the fused lambdoid suture. The head shape appears to be trapezoidal when viewed from above.
- Flatness over the site of the fused lambdoid suture – This does not allow the skull to become rounded at the back of the head.
- Mastoid bulge – There is a low skull bump that occurs much lower than the normal side just behind the ear.
- Ear displacement posterior – On the affected flat side the ear will be pulled backwards when viewed from above. This helps distinguish lambdoid suture fusion versus deformational plagiocephaly in which the ear is displaced forward. The ear on the affected side is also lower than the opposite ear with a tilted cranial base.
The treatment of lambdoid craniosynostosis causing posterior plagiocephaly involves undergoing skull reconstruction with a craniofacial plastic surgeon and a pediatric neurosurgeon. The goals of surgery are to correct the skull deformity. Typically we aim to address width, height, and length as well as creating a more natural curve and roundness to the skull. We also aim to improve space for the brain to continue to grow.
References:
Shillito J Jr, Matson DD. Craniosynostosis: a review of 519 surgical patients. Pediatrics 1968; 41:829.