Imaging of Distal Dural Ring Plane and Paraclinoid Internal Carotid Artery Aneurysms with 3D Rotational Angiography / 신경중재치료의학

PURPOSE: The distal dural ring (DDR) plane separates the intradural from extradural paraclinoid internal carotid artery (ICA) aneurysm. The purpose of this study was to evaluate the feasibility of the localization of the DDR plane drawn by the bony landmarks in patients with paraclinoid ICA aneurysms at 3D rotational angiography (3DRA). MATERIALS AND METHODS: 13 consecutive patients who underwent a 3DRA for the evaluation of 16 paraclinoid ICA aneurysms were reviewed retrospectively. On a dedicated workstation, multiplanar reconstruction (MPR) image along the virtual plane of DDR was reconstructed from the mask run image of 3DRA. Three bony landmarks were used to locate virtual plane of DDR: tuberculum sellae, inferior root of anterior clinoid process (ACP) and supero-medial aspect of optic strut. The MPR image was fused with 3D volume-rendered reconstruction image. Medial and posterior inclination angle of virtual plane of DDR was measured. The location of the paraclinoid ICA aneurysm was categorized into indradural, transdural, and extradural. RESULTS: In all cases, the DDR plane was identified and the relationship between the DDR plane and the paraclinoid ICA aneurysm was successfully determined on fusion image of 3DRA mask and contrast runs by dual volume visualization. The aneurysm locations determined with 3DRA were 8 intradural, 6 transdural and 2 extradural. The medial and posterior inclination angles of DDR plane ranged at 8 to 43degrees(mean 17.4degrees), and -2 to 20degrees(mean 6.4degrees), respectively. CONCLUSION: Localization of the paraclinoid ICA aneurysm in relation to the virtual plane of DDR is feasible with 3DRA and dual volume visualization.

Clinical Implication of the Clinoid(C5) Internal Carotid Artery and Dural Rings: A Microsurgical Anatomy

To describe the detailed microsurgical anatomy of the clinoid(C5)segment of the internal carotid artery(ICA) and surrounding structures and clarify the anatomical relationships of this region emphasizing their clinical relevance, authors examined in 70 specimens from 35 formalin fixed cadaveric heads. Removal of the anterior clinoid process exposes the C5 segment of the ICA which is encircled by the thin inner dural layer of the cavernous sinus wall. Opening this membrane enables entrance into a narrow space that communicates with cavernous sinus through the proximal dural ring. Unlike the dura of the distal dural ring that is tightly attached to the ICA, the proximal dural ring is always incompetent. The C5 segment of the ICA has been considered by the majority of authors to be extracavernous. This understanding developed because most investigators overlooked the thin inner dural layer encircling the clinoid ICA. The narrow space between the inner dural layer and the ICA communicates with cavernous sinus through an incompetent proximal dural ring. Therefore, the clinoid ICA should be considered to be the most rostral portion of the cavernous (C4)segment of the ICA. The proximal dural ring is a surgical landmark rather than a true dural ring.