Microsurgical Anatomic Features and Nomenclature of the Paraclinoid Region

Abstract

The narrow space between the inner dural layer and the clinoid ICA is continuous with the cavernous sinus via an incompetent proximal dural ring. This space between the clinoid ICA and the inner dural layer contains a variable number of veins that directly communicate with the cavernous plexus. Given the inconstancy of the venous plexus surrounding the clinoid ICA, we think that categorical labeling of the clinoid ICA as intracavernous or extracavernous cannot be justified.

Comparison of the effectiveness of using the optic strut and tuberculum sellae as radiological landmarks in diagnosing paraclinoid aneurysms with CT angiography

“…11,21 This small pouch, termed the carotid cave by Kobayashi et al, 11 is present in 68% to 90% of cadaveric specimens 6,9,19 and is where the paraclinoid aneurysms of the medial type (or posterior type with a medial component), carotid cave, and superior hypophyseal artery aneurysms arise. Aneurysms of these types can be intradural and are at risk for subarachnoid hemorrhage.…”

“…The distal dural ring (DDR) is the anatomical boundary between the intra-and extradural segments of the internal carotid artery (ICA) in the paraclinoid region. 2,9,19,24 Some studies tried to delineate the DDR with imaging methods and differentiate the aneurysm in the vicinity of the anterior clinoid process (ACP). 5,16,23 However, these studies either lacked direct surgical confirmation or comprised a small case number.…”

Distinction between Intradural and Extradural Aneurysms Involving the Paraclinoid Internal Carotid Artery with T2-Weighted Three-Dimensional Fast Spin-Echo Magnetic Resonance Imaging

“…It is continuous with the roof of the cavernous sinus along its lateral aspect, overlying the superior surface of the anterior clinoid process, and is also continuous with the diaphragma sellae along its posteromedial aspect and the dura mater covering the tuberculum sellae along its anteromedial aspect 2,11,13,22) . Clinically, it is critical to discriminate between aneurysms proximal to the dural ring and aneurysms distal to the dural ring, because their locations determine surgical indications and the patient's prognosis 4,7,11,18) . If an unruptured proximal carotid aneurysm can be demonstrated with certainty to lie below the dural ring, the risk of subsequent SAH is extremely low, since the aneurysm is protected by the overlying anterior clinoid process and dural reflection 1,14) .…”

“…The natural history of aneurysms involving the paraclinoid area varies based on their anatomic locations and hence the precise localization by neuroimaging study in preoperative period has been one of the most interesting and important problems in clinical neurosurgery 4,7,11,18,24,25) . Aneurysms identified as being completely intradural are at risk for subarachnoid hemorrhage (SAH), and usually require preventive endovascular or surgical treatment.…”

“…Preoperative delineation of the distal dural ring and exact localization of the aneurysm in relation to the cavernous sinus structures continue to be critical clinical issues, but catheter angiography or other conventional imaging modalities have failed to localize these aneurysms exactly 10,11,18) . As a result of recent advances in magnetic resonance (MR) technology, T2-weighted three-dimensional (3-D) fast spinecho (FSE) MR imaging allows for an easy examination of the brain using thin sections and a high signal-to-noise ratio (SNR) 16,19,21,27) .…”