Volumetric Analysis of Anterior Versus Posterior Cranial Vault Expansion in Patients With Syndromic Craniosynostosis

Background: Syndromic craniosynostosis is associated with a high incidence of elevated intracranial pressure. The most common treatment paradigm is to perform anterior cranial vault reconstruction in infancy followed later by possible expansion of the posterior cranial vault and midface advancement. Recently, however, posterior cranial vault expansion has been advocated as an initial step in treatment. We sought to quantify volumetric changes with anterior versus posterior cranial vault surgery in these patients. Materials and Methods: We reviewed patients with syndromic brachycephalic craniosynostosis treated in our unit from 2002 to 2009 with existing preoperative fine-cut computed tomographic scans. Using computer software (Analyze; Mayo Clinic, Rochester, MN) and computed tomographic data, the senior author simulated both anterior and posterior cranial vault expansions. Expansion was simulated with a series of translational advancements of the separated segments. Volumetric data were compared for each simulated procedure. Results: Thirteen patients underwent simulated cranial vault reconstructions. At 2, 10, and 20 mm of anterior advancement, the mean increase in intracranial volume was 1.8%, 8.8%, and 17.7%, respectively, whereas posterior advancements achieved 2.4%, 11.9%, and 23.9%, respectively. On average, posterior cranial vault reconstruction created 35% more relative expansion than anterior expansion at equivalent degrees of advancement (P < 0.001). In all simulations, posterior cranial vault reconstruction created greater intracranial volume changes than anterior reconstructions. Conclusions: This simulation demonstrates that, in syndromic brachycephalic craniosynostosis, posterior cranial vault advancement achieves approximately 35% greater intracranial volume expansion compared with equivalent degrees of anterior cranial vault advancement. This may help guide decisions in treatment sequencing of patients with syndromic craniosynostosis.