Plastic and Reconstructive Surgery, Global Open
PURPOSE: Previous investigations of intracranial volume (ICV) in patients with metopic craniosynostosis have yielded mixed results and are limited by the number of patients included in the study sample. Additionally, no studies have characterized the impact of metopic synostosis on intracranial volume change accompanying growth. In this study, we sought to determine if metopic patients had significantly different intracranial volumes than normal, healthy children. We also compare standardized
... pare standardized growth curves of intracranial volume change in normal patients and patients with metopic craniosynostosis. METHODS: An IRB-approved retrospective review was performed of patients with metopic craniosynostosis at our institution. Intracranial volumes were calculated from manually segmented preoperative CT scans. Structural MRI data for normal children were acquired from the NIH Pediatric MRI Data Repository. Intracranial volumes were calculated in FreeSurfer. Multivariate linear regression including age, gender and diagnosis (i.e. metopic and normal) was performed to determine the impact of metopic craniosynostosis on intracranial volume. To compare intracranial volume growth in normal patients and patients with metopic craniosynostosis, a term defining the interaction between age, diagnosis and their effect on intracranial volume was added to the linear regression model. A best fit logarithmic curve of intracranial volume growth was generated for metopic patients and compared to a best fit logarithmic curve for normal patients. RESULTS : Data were available for 73 metopic craniosynostosis patients (52 males, 21 females; age 1-21 months). 270 MRIs of normal, healthy children were available (141 males, 129 females, age 1-24 months). Mean metopic ICV was lower than normal ICV within the first 3-6 months (14 metopic patients, mean ICV 646.59cc vs 28 normal patients, mean ICV 903.91cc, p=0.002), 6-9 months (26 metopic patients, mean ICV 737.92cc vs 33 normal patients, mean ICV 868.81cc, p=0.005) and 9-12 months of life (19 metopic patients, mean ICV 848.01cc vs 29 normal patients, mean ICV 956.62cc, p=0.038). When controlling for age and gender, the difference in intracranial volume associated with metopic synostosis ranged from 112.67cc (13%) to 304.37cc (32%), with the most significant effect from age 3-6 months (304.4cm3, 32%). There was no difference in intracranial volume after 12 months of age (8 metopic patients, mean ICV 997.65cc vs 96 normal patients, mean ICV 1000.11cc, p=0.916). Intracranial volume growth in patients with metopic synostosis was defined by a significantly different growth equation than normal patients (metopic: y=230.61ln(x)+323.0, normal: y=103.89ln(x)+390.4; p=0.005). Compared to normal patients, metopic patients demonstrated more rapid growth velocity from 1-3 months (126.7 vs 57.1cm 3 / month), 3-6 months (53.3 vs 24.0cm 3 /month), 6-9 months (31.2 vs 14.1cm 3 /month) and 9-12 months (22.1 vs 9.9cm 3 / month). CONCLUSION: In the first year of life, patients with metopic synostosis have significantly reduced intracranial volumes, yet greater than normal intracranial volume growth velocity. It appears the restrictive effect of metopic synostosis relative to normal patients originates, in part, from disparities of intracranial volume at birth, rather than restricted calvarial growth in early life. As a result, cranial vault reconstruction targeting volume expansion should be performed in early life to more rapidly achieve normal volumes in these patients.