APPLIED ANATOMY OF THE POSTERIOR SINUSES IN RELATION TO THE OPTIC-NERVE, TRIGEMINAL NERVE, AND CAROTID-ARTERY

Retrobulbar hemorrhage and visual loss are among the most serious comp lications of endoscopic sinus surgery. To minimize the occurrence of t hese risks, the surgeon's knowledge of the specific locations of the n eurovascular structures is of paramount importance. In this study, the location of the internal carotid artery (ICA), optic nerve, trigemina l nerve, and anterior and posterior ethmoidal arteries were evaluated by cadaver dissection and anatomic and radiographic measurements. Fift y cadavers were studied using endoscopic techniques, calibrated instru ments, and photographic documentation. The average distances from the columella to the optic nerve and ICA were 8.31 cm and 8.57 cm respecti vely. Mean distances to the anterior ethmoidal artery, posterior ethmo idal artery ostium of the sphenoid, and posterior wall of the sphenoid sinus were also determined. Measurements derived from 50 normal crani al MRI studies yielded similar results. The ICA was clearly identified in 95%, and the optic nerve in 72% of sagittal MRI studies. The inter relationship of the maxillary division of the trigeminal nerve with th e lateral sphenoid wall, optic nerve, and carotid artery was also stud ied. Sagittal section MRI scans were very useful in determining the cr itical relationships between the optic nerve, carotid artery, and sphe noid sinus. Comparisons and contrasts are made between the usage of CT scans and MRI in the delineation of these structures.