Applied Anatomy of the Posterior Sinuses in Relation to the Optic Nerve, Trigeminal Nerve, and Carotid Artery

Abstract

Retrobulbar hemorrhage and visual loss are among the most serious complications of endoscopic sinus surgery. To minimize the occurrence of these risks, the surgeon's knowledge of the specific locations of the neurovascular structures is of paramount importance. In this study, the location of the internal carotid artery (ICA), optic nerve, trigeminal nerve, and anterior and posterior ethmoidal arteries were evaluated by cadaver dissection and anatomic and radiographic measurements. Fifty cadavers were studied using endoscopic techniques, calibrated instruments, and photographic documentation. The average distances from the columella to the optic nerve and ICA were 8.31 cm and 8.57 cm respectively. Mean distances to the anterior ethmoidal artery, posterior ethmoidal artery, ostium of the sphenoid, and posterior wall of the sphenoid sinus were also determined. Measurements derived from 50 normal cranial MRI studies yielded similar results. The ICA was clearly identified in 95%, and the optic nerve in 72% of sagittal MRI studies. The interrelationship of the maxillary division of the trigeminal nerve with the lateral sphenoid wall, optic nerve, and carotid artery was also studied. Sagittal section MRI scans were very useful in determining the critical relationships between the optic nerve, carotid artery, and sphenoid sinus. Comparisons and contrasts are made between the usage of CT scans and MRI in the delineation of these structures.