Neurosurgical Anatomy of the Internal Carotid Artery: Magnetic Resonance Imaging Study of the Sellar Region

BACKGROUND: Transsphenoidal surgical approaches involve dissection of the posterior wall of the sphenoid sinus in close proximity to the internal carotid arteries. To reduce the risk of vascular injury, a detailed study of embalmed cadavers' sellae was conducted and found the internal carotid artery approached within 4 mm of the midline in 10% of cases, and the closest intercarotid distance (ICD) occurred in the cavernous sinus, sphenoid sinus, and supraclinoid segments in 82%, 14%, and 4% of cases, respectively. These measurements have not previously been compared with living patients with modern imaging techniques. METHODS: This study measured the closest ICD of 233 coronal magnetic resonance imaging head scans from 183 patients (male = 88, female = 95) at the cavernous sinus, sphenoid sinus, or supraclinoid segments of the internal carotid artery. ICD at the sphenoid sinus was taken for all scans. RESULTS: The internal carotid approached within 4 mm of the midline in 1.3% of cases. The closest ICD occurred in the cavernous sinus, sphenoid sinus, and supraclinoid segments in 24.5%, 35.8%, and 39.7%, respectively. Both results were significantly different from previous cadaveric studies (chisquared tests, P = 1.4 x 10(-4) and P = 6.1 x 10(-8), respectively). CONCLUSIONS: Surgically relevant measurements of the carotid arteries in the sellar are different in cadavers and living subjects. This is likely due to postmortem changes of surrounding structures. This study suggests clinically relevant anatomic studies using measurements taken from cadaveric specimens be updated with modern imaging techniques taken from living patients.