Evaluation of changes in posterior cranial fossa and cerebellum in patients with Chiari type 1 malformation

BACKGROUND: Chiari type I malformation (CMI) is a congenital or acquired condition characterized by the descent of the cerebellar tonsils 3-5 mm or more below the foramen magnum (FM). Although its etiopathogenesis is not yet fully known, it is assumed that decreased posterior cranial fossa (PCF) volume due to paraxial mesodermal insufficiency may play a critical role. This study aimed to investigate the morphological changes in the PCF and cerebellum in CMI patients compared to healthy individuals. MATERIALS AND METHODS: Retrospective morphometric analyses were performed using magnetic resonance (MR) images obtained from the archives of the Department of Radiology, Selçuk University Faculty of Medicine. 50 patients with CM1 (36 females, 14 males) and 50 matched healthy controls (36 females, 14 males) were included in the study. Posterior cranial fossa length and angle measurements were evaluated together with cerebellar dimensions. RESULTS: A significant decrease in clivus length, Klaus index, supraoccipital length and PCF height was demonstrated in the CMI group compared to controls. Conversely, Welcher basal angle, Boogard angle, nasion-basion-opisthion (NBO) angle and cerebellar height were found to be increased. CONCLUSIONS: In patients with CMI, a reduction in total PCF dimensions and an increase in angular measurements associated with platybasia were observed. These findings are thought to contribute to a better understanding of PCF morphology in CMI and to provide valuable guidance for neurosurgeons in the planning and execution of surgical interventions aimed at minimizing intraoperative complications.