Morphometric and Radiomorphometric Study of the Correlation Between the Foramen Magnum Region and the Anterior and Posterolateral Approaches to Ventral Intradural Lesions.

To identify the range of dimensional morphometric variability correlated to the basilar and condylar part of the occipital bone, which may affect the choice of approach to ventral intradural foramen magnum (FM) lesions. In total, 25 dry skulls and 50 head computed tomography (CT) scan results have been assessed in detail, focusing on the FM, occipital condyles, jugular tubercles (JT), and hypoglossal canals (HC). A morphometric analysis has been carried out using linear and angular measurements to estimate the range of the dimensional variability of these structures. Data were presented as mean ± standard deviation, ranges, and interquartile range on a boxplot. The sagittal intercondylar angle (SICA) and anterior condylar angle (ACA) have been found to be important in estimating the axial orientation of the condyles, whereas the JT-HC interline ratio has indicated the prominence of the tubercles. The SICA and ACA have exhibited high variability. The average JT-HC interline ratio was 0.8. Wider SICA-ACA and higher JT-HC interline ratio make the posterolateral approach advantageous. An anterior medial or far-medial endoscopic route is indicated in opposite conditions. In this study, two illustrative cases have been reported. A cautious preoperative morphometric evaluation of the FM region must be considered prior to using tailored and safe anterior endoscopic and posterolateral approaches to ventral intradural lesions to identify the advantages of a certain corridor as much as possible, thereby minimizing the risk of complications.