Lambdoid synostosis is the rarest type of Craniosynostosis occurring approximately 1 in 40,000 births. It is important that a specialist differentiate between positional deformity and Lambdoid synostosis. This two-sided suture is located on the back of the skull and is shaped like an upside down V. When viewed from above the affected side of the back of the head is flatter than the opposite side. One marker in Lambdoid synostosis is a bump located behind the ear on the same side of the fused suture. Also the ear on the side of the flatness would be pulled “back” (rather than pushed forward like that seen in positional deformity). The suture acts as a gravitational pull and everything will shift toward the fused suture.
True lambdoid synostosis, if left untreated, results in pronounced craniofacial asymmetry. Although a diversity of clinical presentations exists, diagnostic features include occipital flattening, an ipsilateral occipitomastoid bulge, and a contralateral hemifacial deficiency. Posterior vault switch cranioplasty is an effective treatment for true lambdoid synostosis when performed in the first year of life.