Neurosurgical Anatomy of the Internal Carotid Artery: An MRI Study of the Sellar Region.

BACKGROUND: Trans-sphenoidal 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 4mm of the midline in 10% of cases, and the closest inter-carotid distance (ICD) occurred in the cavernous sinus, sphenoid sinus, and supra-clinoid segments in 82%, 14%, and 4% of cases respectively. These measurements have not previously been compared to living patients with modern imaging techniques.

METHODS: This study measured the closest ICD of 233 coronal, MRI head scans from 183 patients (M=88, F=95) at the cavernous sinus, sphenoid sinus, or supra-clinoid segments of the internal carotid artery. ICD at the sphenoid sinus was taken for all scans.

RESULTS: The internal carotid approached within 4mm of the midline in 1.3% of cases. The closest ICD occurred in the cavernous sinus, sphenoid sinus, and supra-clinoid segments in 24.5%, 35.8%, and 39.7% respectively. Both results were significantly different to previous cadaveric studies (chi-squared tests, p=1.4x10-4 and p=6.1x10-8 respectively).

CONCLUSION: Surgically relevant measurements of the carotid arteries in the sellar are different in cadavers and living subjects. This is likely due to post-mortem changes of surrounding structures. This study suggests clinically relevant anatomical studies utilising measurements taken from cadaveric specimens be updated with modern imaging techniques taken from living patients.