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Making The Diagnosis In Sagittal Craniosynostosis—It’s Height, Not Length, That Matters
Jessica Daviana Blum, MSc, Daniel Cho, MD, PhD, Dillan F. Villavisanis, BA, Liana Cheung, MBBS, Jinggang Ng, MA, Scott P. Bartlett, MD, Jordan W. Swanson, MD, MS, Jesse A. Taylor, MD.
Children's Hospital of Philadelphia, Philadelphia, PA, USA.

PURPOSE: This study assesses the diagnostic reliability of a novel photogrammetric measurement to distinguish sagittal craniosynostosis (SS) from control and false positive cases (SNS).
METHODS: All head CT imaging at our institution between 2014-2020 was reviewed for patients with sagittal synostosis (SS, n = 177), patients with suspected sagittal craniosynostosis based on clinical examination but normal head CT (SNS, n = 30), and controls (n = 100). A novel measurement reflecting the anterior-posterior location of the vertex was measured by an angle drawn between the cranial vertex, nasion, and opisthocranion (VNO) in profile view with the head in a neutral position (Figure 1). NilRead Enterprise Viewer (Hyland Software, Inc. Westlake, OH) and Microsoft PowerPoint (Microsoft Corp. Redmond, Wash.) were used to measure VNO angles on 3D Head CT Reconstructions (n = 307) and clinic photos (n = 172) respectively. Three masked raters measured VNO angle on clinic photos, and one author (DYC) reviewed all photos to binarily determine the presence or absence of frontal bossing (FB) and occipital bulleting (OCB). Patients’ medical charts were reviewed for demographic information, preoperative cephalic index (CI), and operative approach when indicated. To determine the best combination of clinical findings to distinguish sagittal synostosis, Receiver operating characteristic analysis (ROC) was conducted for the various permutations of VNO, FB, OCB, and CI.
RESULTS: Mean age at pre-operative head CT was 9.5 months for the SS cohort, 4.2 months for the SNS cohort, and 8.9 months for the control cohort (p = .327). Mean age at the time of pre-operative clinical photo was 9.5 months for the SS cohort and 4.2 months for the SNS cohort (p = .149). Pearson correlations revealed no significant association between age and VNO angle for any group. The average VNO angle measured on clinical photos was 54.7°±3.8° for the SS group, 43.1°± 2.2° for the SNS group, and 41.1°± 3.7° for controls (p<.001). Three-rater analysis yielded a moderate intraclass correlation coefficient of 0.742 (p=.004). ROC analysis yielded a cut-off of 50° to determine SS versus SNS and controls. AUC for the permutations of VNO angle, FB, OCB, and CI ranged from .187 to .956 (Figure 2). The largest AUC value of .956 was obtained when for VNO angle alone, with a corresponding sensitivity and specificity of 96.6% and 99.2% respectively.
CONCLUSION: Measurement of the VNO angle is a reliable screening tool to diagnose sagittal craniosynostosis, with an angle of 50° or more suggesting suture synostosis. This method relies on the relationship between the anterior displacement of the cranial vertex and occipital bulleting to approach the diagnostic accuracy of CT imaging.


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