Relationship between the ophthalmic artery and the dural ring of the internal carotid artery Clinical article

Object. The ophthalmic artery (OphA) usually arises from the intradural internal carotid artery (ICA), and the extradural origin has also been known. However, the interdural origin is extremely rare. The purpose of this paper was to clarify the origin of the OphA in patients with a paraclinoid aneurysm in the ICA based on intraoperative findings. Methods. The authors retrospectively examined 156 patients who underwent direct Surgical treatment for 166 paraclinoid aneurysm, during a 17-year period. Based on intraoperative findings, 119 ophthalmic arteries were analyzed with respect to their origins. Results. The OphA originated from the intradural ICA on 102 sides (85.7%), extradural on 9 (7.6%), and interdural on 8 (6.7%). Although the extradural origin might be recognized preoperatively, it was difficult to distinguish the interdural origin of the OphA from the intradural one. Conclusions. The incidence of the interdural origin was 6.7% and was not as rare as the authors expected. Neurosurgeons should know the possible existence of the interdural origin of the OphA to section the medial side of the dural ring. (DOI: 10.3171/2008.11.JNS08766)