Turkish Neurosurgery 2011 , Vol 21 , Num 2
Anatomical Variations of the Foramen Magnum, Occipital Condyle and Jugular Tubercle
Emel AVCI1, Ahmet DAGTEKIN1, A. Hakan OZTURK2, Engin KARA3, Nail Can OZTURK2, Kutluay ULUC4, Erinc AKTURE4, Mustafa K. BASKAYA4
1Mersin University, Faculty of Medicine, Department of Neurosurgery, Mersin, Turkey
2Mersin University, Faculty of Medicine, Department of Anatomy, Mersin, Turkey
3Mersin University, Faculty of Medicine, Department of Radiology, Mersin, Turkey
4University of Wisconsin and William S. Middleton Veterans Administration Hospital, Department of Neurological Surgery, Madison, Wisconsin, USA
DOI : 10.5137/1019-5149.JTN.3838-10.1 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. Keywords : Foramen magnum, Occipital condyle, Jugular tubercle, Skull base, Anatomical variations

Corresponding author : Mustafa K. Baskaya, m.baskaya@neurosurg.wisc.edu