Plasticity of the endocranial base in nonsyndromic craniosynostosis.

Limited in vivo data exist on the dysmorphology of the cranial base in nonsyndromic craniosynostosis. Few studies have documented the effect of calvarial surgery for synostosis on endocranial morphology. Previous work has suggested that the dysmorphology of the endocranial base is diagnostically specific for metopic, sagittal, and unicoronal sutures. The purpose of this study was to further evaluate the endocranial base in infants with nonsyndromic craniosynostosis by testing the hypothesis that the dysmorphology is, to some degree, a secondary deformation rather than a primary malformation. Three questions were addressed: (1) Can individuals reliably identify affected suture-specific endocranial-base morphology using standard templates? (2) Does calvarial surgery in infancy for craniosynostosis affect the perception of endocranial-base morphology? and (3) Does calvarial surgery in infancy for nonsyndromic craniosynostosis normalize the endocranial base?In this study, three-dimensional volumetric reconstructions from archived computed tomography digital data were processed using the ANALYZE imaging software. Dysmorphology was assessed by nine independent, blinded skilled observers who reviewed two separate sets of images of endocranial bases. Both sets contained images from the same patients: one set contained preoperative images, and the other contained images of the endocranial base 1 year after calvarial surgery. Observers were asked to sort each set into four suture-specific diagnostic groups: normal, unicoronal, metopic, and sagittal. Each set contained 10 patients with unicoronal synostosis, 10 with metopic synostosis, 10 with sagittal synostosis, and four normal patients. Seventy-eight percent of the total number of preoperative images were correctly sorted into the suture-specific diagnostic group, whereas only 55 percent of the total number of postoperative images were correctly matched. With regard to the individual sutures, the results were as follows (data are presented as preoperative accuracy versus postoperative accuracy): metopic, 76 percent versus 44 percent; sagittal, 58 percent versus 34 percent; unicoronal, 100 percent versus 79 percent; and normal, 83 percent versus 72 percent. Although 36 of 306 total images per group (12 percent) actually represented normal patients, the observers called 72 of 306 normal (24 percent) in the preoperative set versus 110 of 306 normal (36 percent) in the postoperative set. In conclusion, (1) the endocranial dysmorphology of nonsyndromic craniosynostosis is recognizably specific to the affected suture; (2) calvarial surgery for nonsyndromic craniosynostosis normalizes the endocranial base qualitatively with regard to the diminished ability of raters to identify the primary pathology; and (3) the documented postoperative changes in endocranial base morphology after calvarial surgery for nonsyndromic craniosynostosis in infancy indicates that a major component of that dysmorphology is a secondary deformity rather than a primary malformation.