Identification of the Distal Dural Ring and Definition of Paraclinoid Aneurysms According to Bony Landmarks on 3-Dimensional Computed Tomography Angiography: A Cadaveric and Radiological Study

Abstract

BACKGROUND Determining if paraclinoid aneurysms are intradural or extradural is critical for surgical planning. OBJECTIVE To create an easily reproducible diagnostic method based on bony anatomy that precisely locates the distal dural ring (DDR) to determine the position of paraclinoid aneurysms as intradural, transitional, or extradural. METHODS Bilateral anatomic dissections of 10 cadaveric heads (20 sides) were performed to evaluate DDR anatomy. We observed a plane that reflects the position of the DDR passes through 4 bony landmarks: 1) The anterior clinoid-internal carotid artery intersection, 2) the optic strut, 3) the optico-carotid elevation, and 4) the base of the posterior clinoid process. This landmark-based plane can thus define the location of the DDR using 3-dimensional computed tomography angiography (CTA). This was confirmed in 27 surgical patients with intradural/transitional aneurysms and 7 patients with extradural aneurysms confirmed with magnetic resonance imaging (MRI). The DDR plane method easily classified aneurysm locations as intradural (above the DDR plane), extradural (below the DDR plane), or transitional (the DDR plane crosses the aneurysm). The aneurysm's location was subsequently confirmed intraoperatively or with MRI. RESULTS The DDR plane method determined if paraclinoid aneurysms were intradural, transitional, or extradural in all 34 cases examined. The visibility of the anatomic features that define the DDR plane was also verified in 82% to 89% of CTA images from 100 patients. CONCLUSION The DDR plane method provides a useful diagnostic tool to evaluate the position of the DDR and determine the anatomic location of paraclinoid aneurysms.

The diagnostic accuracy of MRI in determining the relations between paraclinoid aneurysms and the cavernous sinus

“…However, the OS represents only the anterior limit of the DDR that is not applied to all paraclinoid aneurysms that rise from different portions of the ICA. Therefore, Scerbak et al [ 31 ] proposed a DDR plane based on four bony landmarks: (1) the intersection between the anterior clinoid and the ICA; (2) optic strut, (3) optico-carotid elevation, and (4) posterior clinoid process. They found 100% agreement between the radiological impression and surgical findings regarding the extension of the paraclinoid aneurysm in the subarachnoid space; however, these methods provide indirect evaluation of the DDR disposition.…”

Letter to the Editor: Commentary on Coil Embolization of Traumatic Ophthalmic Artery Aneurysm: Case Report (Korean J Neurotrauma 2022;18:98–102)

“…For example, maximum intensity projection images to observe the ACP and OAO, and magnetic resonance image to confirm the location of the DDR would be useful. 1 2 3) Supplementary brain imaging studies could clarify the case explanations and validity for the decision of the author.…”