Abstract

Abstract Purpose Chiari malformation type II (CM-II) is a congenital anomaly commonly associated with myelomeningocele (MMC), a severe form of open spina dysraphism. This study aimed to evaluate both supratentorial and infratentorial volumes in MMC infants with and without CM-II. Methods We conducted a single-center, retrospective study of 52 MMC infants treated between April 2006 and July 2023. Infants were classified as non-CM-II or CM-II based on the presence of cerebellar displacement. All patients underwent computed tomography (CT) at 0 months of age. Volumetric parameters included intracranial volume (ICV), lateral ventricles volume (LVV), posterior cranial fossa volume (PCFV), cerebellum volume (CBMV), and brainstem volume (BSV). LVV represented supratentorial structures, while PCFV, CBMV, and BSV represented infratentorial structures. Results CM-II was diagnosed in 30 infants (57.7%). Correlation analysis revealed significant negative correlations between supratentorial (LVV) and infratentorial volumes (PCFV, CBMV, and BSV), and positive correlations among volumes within the same space(e.g., PCFV, CBMV, and BSV). CM-II infants exhibited significantly larger ICV ( p = 0.04) and LVV ( p < 0.001), but smaller PCFV ( p < 0.001) and CBMV ( p < 0.001) than non-CM-II infants. LVV was the best predictor for distinguishing non-CM-II from CM-II (area under the curve = 0.91). Conclusion This study identified positive correlations within the same space and negative correlations between supratentorial and infratentorial volumes. LVV emerged as a critical indicator of CM-II, reflecting the relationship between reduced infratentorial space and enlarged supratentorial ventricles (hydrocephalus). These findings provide insights into the pathophysiology and clinical implications of CM-II in MMC patients.