Effects of Posterior Vault Distraction Osteogenesis on Ventricular Morphology and Volume

INTRODUCTION: Patients with cephalocranial disproportion may be treated by posterior vault distraction osteogenesis (PVDO) to expand intracranial volume (ICV). The increase in ICV may reverse or prevent increased intracranial pressure (ICP) and its sequelae. ICV expansion may additionally improve ventricular patency and cerebrospinal fluid (CSF) hydrodynamics. However, the relationship between cranial vault expansion by PVDO and ventricular volume has yet to be quantified. This study aims to conduct pre- and postoperative morphometric and volumetric ventricular analyses to better understand the effects of PVDO on cranial CSF hydrodynamics. METHODS: All patients who had undergone PVDO at our institution between 2008 and 2022 with appropriate pre- and postoperative cranial computed tomograms (CT) were retrospectively reviewed. Patients with intervals greater than one year between imaging and PVDO were excluded, as were patients who had undergone additional cranial procedures between images. The ventricular system was isolated from pre- and postoperative images for volumetric analysis. All measures were normalized to total cerebral volume to control for inter- and intrapersonal variations in cerebral dimensions. Linear mixed effects models were used to compare normalized pre- and postoperative dimensions. RESULTS: Eleven patients were included. Mean age at PVDO was 4.51±2.83 years. Three patients had bicoronal synostosis, 2 had multisuture, 5 had pansynostosis, and 1 had unicoronal craniosynostosis. Six patients had a syndromic diagnosis (2 Apert, 1 Crouzon, 1 Muenke, 1 Pfeiffer, 1 Saethre Chotzen). Mean age at pre- and postoperative CT scans were 4.38±2.79 years and 5.01±2.90 years, respectively. Average pre- and postoperative normalized total ventricular volume was 2.36±2.14% and 3.42±2.24% of total cerebral brain volume, respectively. The lateral ventricles were the greatest contributors to total ventricular volume. Pre- and postoperative normalized lateral ventricle volumes were 2.10±1.97% and 3.11±2.14% of total cerebral brain volume, respectively. PVDO was found to significantly increase the normalized volume of the lateral ventricles (β=1.00%, p=0.04), while the expansion in normalized volume of the total ventricular system trended toward significance (β=1.06%, p=0.06). There was no significant change in normalized volume of the third (p=0.33) or fourth ventricles (p=0.82). CONCLUSION: This study provides evidence that a secondary effect of PVDO is a significant increase in ventricular volume. The maximal relative volume increase is obtained in the lateral ventricles, with total relative ventricular volume trending towards significance, as well. These findings have potential implications in the treatment of conditions associated with aberrant ventricular hydrodynamics, such as hydrocephalus. Future works will be critical in quantifying the effects of PVDO on CSF flow and understanding its use as a potential treatment for ventricular pathology.