Lambdoid Synostosis Versus Positional Posterior Plagiocephaly, a Comparison of Skull Base and Shape of Calvarium Using Computed Tomography ImagingHurmerinta, Kirsti DDS, PhD; Kiukkonen, Anu DDS, PhD; Hukki, Jyri MD, PhD; Saarikko, Anne MD, PhD; Leikola, Junnu DDS, PhDJournal of Craniofacial Surgery: September 2015 - Volume 26 - Issue 6 - p 1917–1922 doi: 10.1097/SCS.0000000000002098 Original Articles Buy Abstract Author InformationAuthors Article MetricsMetrics The differential diagnostics between the common positional posterior plagiocephaly and relatively rare lambdoid synostosis is important due to the differences in their treatment plan and clinical management. However, the clinical criteria for the diagnosis of lambdoid synostosis are not clear since there is a considerable overlap in the features of positional posterior plagiocephaly and unilateral lambdoid synostosis. To systematically evaluate the clinical findings in these 2 patient groups, we quantitatively compared the characteristics of endocranial skull base and ectocranial calvarium in 3D computed tomography, in 9 children (mean age 2.9 years) with unilateral lambdoid synostosis and 9 children with positional posterior plagiocephaly. The groups were sex and age matched. Our results show that the skull bases in the lambdoid synostosis are posteriorly shorter and more twisted than in positional posterior plagiocephaly. Anterior twisting was mild in both skull types. Our study confirmed earlier suggested diagnostic feature: prominent ipsilateral mastoidal bossing downward and laterally in all lambdoid skulls. In positional posterior plagiocephaly the bossing was typically not detected. Interestingly, there was a great variation in the position of the ipsilateral ear and external auditory meatus in both patient groups. Thus, neither antero-posterior nor vertical position of ear is a reliable differential diagnostic feature between lambdoid synostosis or positional posterior plagiocephaly. Cleft Palate and Craniofacial Centre, Department of Plastic Surgery, Helsinki University Central Hospital, Helsinki, Finland. Address correspondence and reprint requests to Anu Kiukkonen, PhD, Cleft Palate and Craniofacial Centre, Department of Plastic Surgery, Helsinki University Central Hospital, P.O. Box 266, FI-00029 HUS Helsinki, Finland; E-mail: Anu.Kiukkonen@hus.fi Received 22 February, 2015 Accepted 10 July, 2015 The authors report no conflicts of interest. © 2015 by Mutaz B. Habal, MD.