Supratentorial vs infratentorial posterior calvarial distraction osteogenesis for the increase of ICV in children with syndromic or multi-suture craniosynostosis: a retrospective cohort study.

PURPOSE: Craniosynostosis is the premature and pathological fusion of calvarial sutures. One modality of surgical treatment of syndromic craniosynostosis is posterior calvarial distraction (PCD). This can be either supratentorial or infratentorial. Currently, supratentorial PCD may be regarded as safer but produces a smaller increase in calvarial volume compared to infratentorial PCD. This study quantifies and compares the effectiveness of supratentorial and infratentorial PCD to help guide surgical decision-making. METHODS: The CT and/or MRI scans of 47 cases of craniosynostosis who underwent PCD from the Birmingham Children's Hospital (BCH) were converted to sagittal series multi-planar reformatted (MPR) scans for the manual calculation of ICV. The 47 cases were classified as having undergone either supratentorial or infratentorial PCD using lateral plain film radiographs, with 28 and 32 pairs of pre- and post-operative CT/MRI scans reviewed respectively. RESULTS: A statistically significant difference between supratentorial and infratentorial PCD was observed for the increase in supratentorial volume (STV) (P = 0.0458) and total intracranial volume (TICV) (P = 0.0437), but not for the increase in infratentorial volume (ITV) (P = 0.0697). The relationship for each volume trended towards convergence but was not achieved before the physical limit of 30 mm distraction had been reached. Intraclass correlation coefficient values for agreement of MRI and CT scans for STV, ITV and total ICV were 0.852, 0.864 and 0.854 respectively. CONCLUSION: Our evidence suggests that supratentorial PCD is more effective for increasing ICV in a clinical setting. CT and MRI imaging modalities are acceptably clinically interchangeable for calculating ICV in craniosynostosis.