Lambdoidal Craniosynostosis

GENESIS

Lambdoidal craniosynostosis occurs in approximately 1 in 33,000–40,000 births and is the least common form of craniosynostosis, accounting for only 2% to 5% of all cases. Misdiagnosis of nonsynostotic deformational posterior plagiocephaly with occipital flattening as lambdoidal craniosynostosis has resulted in apparent epidemics of craniosynostosis, in which the proportion of lambdoidal craniosynostosis cases was reported as more than 40% of total craniosynostosis cases in Colorado, United States, and more than 70% in York-Selby, England. Both of these “epidemics” of craniosynostosis arose during the time when Western cultures were shifting their infant sleeping position from prone to supine in an effort to reduce the incidence of sudden infant death syndrome (SIDS). With this change, infants no longer move their heads from one side to the other as they do in the prone sleeping position; thus placing infants on their backs quickly magnified any inequity in resting position such that asymmetric occipital flattening developed in infants with positional torticollis. Because the lambdoid sutures are not readily visualized on skull radiographs, nonvisualization of these sutures in an asymmetrically flattened occiput was interpreted as lambdoidal craniosynostosis. Further complicating this diagnosis is the fact that most lambdoidal craniosynostosis occurs as an isolated anomaly in an otherwise normal child and is frequently associated with muscular torticollis, which suggests that many cases of lambdoidal craniosynostosis are a consequence of fetal compression. Lambdoidal craniosynostosis can result from constraint of the posterior cranium associated with abnormal fetal lie or presentation. Lambdoidal synostosis has no clear genetic etiology. Discordant synostosis has been reported in one monozygotic twin; there is also an unsubstantiated report of concordance in dizygotic twins and a single report of dizygotic twins concordant for contralateral lambdoidal synostosis. There are also reports of children with rare de novo single-gene mutations and chromosome abnormalities who manifest lambdoidal craniosynostosis as one component of a broader pattern of altered morphogenesis.