Volumetric Morphometric Analysis of Posterior Fossa Structures Following Posterior Fossa Decompression with Superficial Durotomy in Chiari I Malformation

Background/Objectives: Posterior fossa decompression (PFD) with superficial durotomy is used in Chiari I malformation to limit the CSF-related complications of complete durotomy and duraplasty, but quantitative volumetric evidence has relied on linear measurements, modest cohorts, and heterogeneous methods. We applied a fully automated deep-learning segmentation pipeline to characterize multi-structure volumetric change after PFD with superficial durotomy.

Methods

Thirty-three patients (24 females and nine males; mean age, 39.2 ± 13.5 years; two pediatric) with symptomatic Chiari I malformation underwent PFD with superficial durotomy. Pre-operative and 6-month post-operative 3D T1-weighted 1.5T MRIs were segmented using nnU-Net, CERES, TotalSegmentator, and nnDetection. Posterior fossa volume (PFV), supratentorial volume, PFV/STV ratio, cerebellar volume, brainstem volume, fourth ventricle volume, basal cisterns’ CSF volume, and tonsillar descent were computed and compared pre/post using paired t-tests or Wilcoxon tests, Cohen’s d with bootstrapped 95% confidence intervals, and Benjamini–Hochberg correction. The pipeline was developed and validated exclusively on 1.5T Siemens Aera data and is not presented as ready for out-of-box use on other scanner platforms without re-validation.