Nonsynostotic occipital plagiocephaly: Radiographic diagnosis of the "sticky suture"

Background: While the clinical differences between nonsynostotic occipital plagiocephaly and lambdoid craniosynostosis have been described, the radiographic differentiation between the two remains obscure. The aim of this study was to characterize morphological differences in the lambdoid suture between nonsynostotic occipital plagiocephaly and lambdoid craniosynostosis. Methods: Computed tomography scans of children clinically diagnosed with nonsynostotic occipital plagiocephaly (n = 26) were compared with computed tomography scans from children diagnosed with lambdoid craniosynostosis (n = 7). Suture and cranial morphology, ear position, and endocranial base angles were qualitatively and quantitatively compared. Results: Nonsynostotic occipital plagiocephaly sutures demonstrated areas of focal fusion (25 percent), endocranial ridg-ing (78 percent), narrowing (59 percent), sclerosis (19 percent), and changes from overlapping to end-to-end orientation (100 percent). No sutures demonstrated ectocranial ridging. All cases of nonsynostofic occipital plagiocephaly presented with ipsilateral occipital flattening, 85 percent with ipsilateral frontal, and 95 percent with contralateral occipital bossing contrast, a greater frequency of sutures in lambdoid craniosynostosis patients demonstrated nearly complete obliteration (p < 0.001) with ectocranial ridging (p < 0.001); significantly more of these patients presented with ipsilateral occipital flattening with compensatory ipsilateral mastoid (p < 0.001) and contralateral parietal (p < 0.01) bossing, producing a trapezoid morphology. Sutures from nonsynostotic occipital plagiocephaly patients showed endocranial ridging, focal fusions, and narrowing, previously reported as lambdoid craniosynostosis. Conclusions: In contradiction to previous reports, lambdoid craniosynostosis is not radiographically unique among suture fusions. This work establishes the radiographic diagnosis of nonsynostotic occipital plagiocephaly.