Plasticity of the endocranial base in nonsyndromic craniosynostosis

Limited in vivo data exist on the dysmorphology of the cranial base in nons yndromic craniosynostosis. Few studies have documented the effect of calvar ial surgery for synostosis on endocranial morphology. Previous work has sug gested that the dysmorphology of the endocranial base is diagnostically spe cific for metopic, sagittal, and unicoronal sutures. The purpose of this st udy was to further evaluate the endocranial base in infants with nonsyndrom ic craniosynostosis by testing the hypothesis that the dysmorphology is, to some degree, a secondary deformation rather than a primary malformation. T hree questions were addressed: (1) Can individuals reliably identify affect ed suture-specific endocranial-base morphology using standard templates? (2 ) Does calvarial surgery in infancy for craniosynostosis affect the percept ion of endocranial-base morphology? and (3) Does calvarial surgery in infan cy for nonsyndromic craniosynostosis normalize the end cranial base? In this study, three-dimensional volumetric reconstructions from archived c omputed tomography digital data were processed using the ANALYZE imaging so ftware. Dysmorphology was assessed by nine independent, blinded skilled obs ervers who reviewed two separate sets of images of endocranial bases. Both sets contained images from the same patients: one set contained preoperativ e images, and the other contained images of the endocranial base I year aft er calvarial surgery. Observers were asked to sort each set into four sutur e-specific diagnostic groups: normal, unicoronal, metopic, and sagittal. Ea ch set contained 10 patients with unicoronal synostosis, 10 with metopic sy nostosis, 10 with sagittal synostosis, and four normal patients. Seventy-ei ght percent of the total number of preoperative images were correctly sorte d into the suture-specific diagnostic group, whereas only 55 percent of the total number of postoperative images were correctly matched. With regard t o the individual sutures, the results were as follows (data are presented a s 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. Altho ugh 36 of 306 total images per group (12 percent) actually represented norm al patients, the observers called 72 of 306 normal (24 percent) in the preo perative set versus 110 of 306 normal (36 percent) in the postoperative set . In conclusion, (1) the endocranial dysmorphology of nonsyndromic craniosyno stosis is recognizably specific to the affected suture; (2) calvarial surge ry for nonsyndromic craniosynostosis normalizes the endocranial base qualit atively with regard to the diminished ability of raters to identify the pri mary 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 sec ondary deformity rather than a primary malformation.