The Northeastern Society of Plastic Surgeons

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Quantitative cranial shape analysis to evaluate patients with delayed non-syndromic sagittal synostosis
Esperanza Mantilla Rivas1, Agnes Goldrich1, Antonio R. Porras, PhD2, Liyun Tu, PhD2, Albert K. Oh, M.D1, Marius G. Linguraru, DPhil2, Gary F. Rogers, M.D1.
1Children's National Medical Center, Washington, DC, USA, 2Sheikh Zayed Institute for Pediatric Surgical Innovation, Washington, DC, USA.

BACKGROUND: Premature fusion of the sagittal suture typically results in scaphocephaly. When diagnosed early, prompt assessment and surgical interventions can reduce the risk of elevated intracranial pressure (ICP). Latent closure of sagittal synostosis with mild or even absent phenotypic changes has been reported, and the risk of raised ICP in such patients is unclear. The cranial index (CI), a bidimensional tool used to diagnose scaphocephaly, in these patients is normal but this metric may not provide a complete picture of cranial shape. The goal of this study is to better quantify the differences in cranial shape in patients with latent isolated sagittal synostosis and normal CI using a proprietary form of shape analysis.
METHODS: We identified 21 patients older than 3 years who presented to our hospital with isolated sagittal synostosis and visibly normal head shape and cephalic index between 2011 and 2016. We quantified the malformations from the CT image of each patient using previously presented methods. First, we segmented the different cranial bones using adaptive thresholding and an in-house graph-cut based algorithm. Then, we compared each cranial shape with its closest normal from a statistical shape multi-atlas built from the cranial shapes of 220 healthy subjects. Local malformations were calculated as the distances between the patient’s cranial shape and its closest normal shape.
RESULTS: During the computation of skull malformation, 3 cases failed due to bad segmentation, leaving 18 cases for analysis. The majority of patients (77.7%) fell within the mesocephalic range (CI 75-84), three patients (16.7%) had a CI >85 while only one patient (5.6%) had a CI below 75% (CI <74.9). Detailed cranial shape analysis of these patients identified 13 patients (72.2%) with a mildly scaphocephalic phenotype (p-value = 0.0001).
CONCLUSIONS: The cranial shape in the majority of patients with latent sagittal fusion is not normal and most demonstrate subtle changes that are consistent with the diagnosis yet are poorly captured by visual exam or cephalic index. Quantitative cranial shape analysis provides a more accurate assessment of cranial malformations in patients with delayed isolated sagittal synostosis, and may provide more complete information to guide treatment options.


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