PVDO (posterior vault distraction osteogenesis) is a technique for expanding the posterior cranial fossa and increasing intracranial volume. To fully widen the posterior cerebral fossa, the authors extended osteotomy posterior to the foramen magnum during PVDO. For this study, scientists aimed to see how effective complete PVDO was at expanding the posterior fossa and treating Chiari malformation type I (CM-I) in patients with craniosynostosis. Between January 2012 and May 2020, patients with craniosynostosis who had complete PVDO were evaluated retrospectively. The foramen magnum was decompressed by removing its posterior rim with a 1-mm Kerrison rongeur after a coronal osteotomy extending to it was performed. Four distractor devices were installed, with the vector of distraction adjusted from the posterior to the inferior-posterior direction depending on the deformity. After complete PVDO, CT and MRI were used to assess changes in intracranial volume, rear cerebral fossa area, and cerebellar tonsillar descent.

The study comprised 11 patients who had craniosynostosis and CM-I simultaneously. The average age was 34.6 ± 24.0 months (continuous variables are expressed as the mean ± SD throughout). One patient reported sleep apnea consistent with CM-I, whereas another had a generic headache. The intracranial volume increased by 24.5% from 1179.6 ± 180.2 cm3 to 1440.6 ± 251.5 cm3 (p = 0.003; preoperative volume increased by 24.5%). The posterior skull base area increased (p = 0.004) from 44.9 ± 19.3 cm2 to 72.7 ± 18.1 cm2. After complete PVDO, all 11 patients’ cerebellar tonsillar descent decreased (preoperative: 10.8 ± 3.7 mm, postoperative: 2.7 ± 3.0 mm; p = 0.003). Five of the 11 patients had their cerebellar tonsillar herniation completely resolved. Unlike traditional techniques, complete PVDO can extend the posterior cerebral fossa more effectively. It also aids in the relief of cerebellar tonsillar herniation. Complete PVDO is a powerful technique for increasing intracranial and posterior fossa volumes in individuals with craniosynostosis and concurrent CM-I.