Anatomical variations of the foramen magnum, occipital condyle and jugular tubercle.

AIM The foramen magnum (FM) is a unique and complex anatomical region. The occipital condyle (OC) and jugular tubercle (JT) are the main bony structures which obscure the anterolaterally situated lesions of the FM.The aim of this study was to revisit the anatomy of the FM region and assess variations of the surrounding structures. MATERIAL AND METHODS Observations, on thirty dry skulls (dried specimens, 60 sides) and ten formalin-fixed cadaveric heads with perfused vessels, were carried out to define the microsurgical anatomy of the FM region. Morphometric analysis and variations of the FM, OC, JT and hypoglossal canal (HC) were noted. Radiological assessment (3D-computed tomography) of the OC, JT, HC were also conducted on dry skulls. RESULTS The short and long OC were demonstrated in 5% and 33% of the specimens, respectively. Flat formation of the JT was determined in 10% and tall JT was found in 23% of the specimens. The comparison of the anatomical measurements and the correspondent radiological mean values did not achieve statistical significance. CONCLUSION The OC and JT are the main bony prominences obstructing the anterolateral surface of the brainstem. Neurosurgeons should be familiar with variations of the structures surrounding the FM in order to perform the safest and widest exposure possible.