Clinoid Segment Research Articles

Saphenous Vein Graft for Bypass of the Maxillary to Supraclinoid Internal Carotid Artery: An Anatomical Short Study

The use of a saphenous vein graft for bypass of the maxillary artery (MA) to the supraclinoid internal carotid artery (ICA) in internal carotid occlusions is investigated. Five adult cadaver sides were used. Dissection required zygomatic arch osteotomy and a pterional craniotomy with extensive removal of the floor of the middle cranial fossa. The MA was found easily medial to infratemporal crest. The clinoidal segment of the ICA was exposed with the removal of the anterior clinoid process intradurally. The bypass graft was 4 to 5 cm long and was sutured end-to-end to the MA and end-to-side to the supraclinoid ICA. When high blood flow is needed in cases with ICA occlusion, such a bypass may be an alternative to superficial temporal (STA)-to-middle cerebral artery (MCA) bypass as well as to common carotid-to-MCA or-ICA bypass, which needs a long vein graft. This type of bypass will provide the opportunity to clip the ICA proximal to the origin of ophthalmic artery, which may inhibit distal embolization.

Microsurgical anatomic features and nomenclature of the paraclinoid region.

We describe the detailed microsurgical anatomic features of the clinoid (C5) segment of the internal carotid artery (ICA) and surrounding structures, clarify the anatomic relationships of structures in this region, and emphasize the clinical relevance of these observations. Furthermore, because the nomenclature of the paraclinoid region is confusing and lacks standardization, this report provides a glossary of terms that are commonly used to descibe the anatomic features of the paraclinoid region. The region surrounding the anterior clinoid process was observed in 70 specimens from 35 formalin-fixed cadaveric heads. Detailed microanatomic dissections were performed in 10 specimens. Histological sections of this region were obtained from the formalin-fixed cadaveric specimens. The clinoid segment of the ICA is the portion that abuts the clinoid process. This portion of the ICA can be directly observed only after removal of the clinoid process. The dura of the cavernous sinus roof separates to enclose the clinoid process. The clinoid segment of the ICA exists only where this separation of dural layers is present. Because the clinoid process does not completely enclose the ICA in most cases, the clinoid segment is shaped more like a wedge than a cylinder. The outer layer of the dura (dura propria) is a thick membrane that fuses with the adventitia of the ICA to form a competent ring that separates the intradural ICA from the extradural ICA. The thin inner membranous layer of the dura loosely surrounds the ICA throughout the entire length of its clinoid segment. The most proximal aspect of this membrane defines the proximal dural ring. The proximal ring is incompetent and admits a variable number of veins from the cavernous plexus that accompany the ICA throughout its clinoid segment. 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.

Clinoid and paraclinoid aneurysms: surgical anatomy, operative techniques, and outcome

Background Paraclinoid or ophthalmic segment aneurysms arise from the internal carotid artery (ICA) between the roof of the cavernous sinus and the origin of the posterior communicating artery. Clinoid aneurysms arise between the proximal and distal carotid dural rings. The complex anatomy of clinoid and paraclinoid ICA aneurysms often makes them difficult to treat by microsurgery. The natural history of these aneurysms varies, based on their location and anatomic relationships. Accurate preoperative assessment of the origin of these aneurysms is therefore a critical aspect of their management. Methods The authors reviewed 35 clinoid and paraclinoid ICA aneurysms operated in 28 patients and classify them according to their anatomic location and angiographic pattern. The operative techniques, surgical outcomes, and indications for surgery are reviewed. Results Based on surgical anatomy and angiographic patterns, the aneurysms were classified into two categories: clinoid segment and paraclinoid (ophthalmic) segment. The clinoid segment aneurysms consisted of medial, lateral and anterior varieties. The paraclinoid aneurysms could be classified topographically into medial, posterior and anterior varieties, or based on the artery of origin into ophthalmic, superior, hypophyseal, and posterior paraclinoid aneurysms. Ophthalmic aneurysms were most common (40%), followed by posterior ICA wall aneurysms (29%), superior hypophyseal aneurysms (14%), and clinoid aneurysms (17%). Twenty patients (71%) had single aneurysms. Of the remaining eight, six had bilateral aneurysms and two had unilateral multiple aneurysms. Of the 35 aneurysms, 32 were clipped satisfactorily, as confirmed by intraoperative or postoperative angiography. One small broad-based aneurysm was wrapped, and two others were treated by trapping and bypass techniques. Three patients who had bilateral aneurysms underwent successful clipping of four contralateral, left-sided aneurysms via a right frontotemporal, transorbital approach. On follow-up (mean, 39 months), 25 patients were in excellent condition (returned to their prior occupation), two were in good condition (independent, but not working), and one died postoperatively of vasospasm. Conclusion Our increased knowledge of anatomy and refinements in operative techniques have greatly improved the surgical treatment of clinoid and paraclinoid aneurysms.

Surgical Treatment of Paraclinoid and Ophthalmic Aneurysms

Paraclinoid aneurysms include those arising from the ophthalmic segment and from the distal cavernous carotid artery or clinoid segment. Three aneurysm variants originate from the ophthalmic segment: ophthalmic artery, superior hypophyseal artery, and dorsal types. Clinoidal segment aneurysms arise from the carotid artery in the interval between the carotid oculomotor membrane proximally and the dural ring distally, and include anterior-lateral and medial variants. With proper exposure and a firm understanding of the parasellar osseous, dural, and vascular anatomy, most paraclinoid aneurysms are occluded with low risk to the brain or visual apparatus.

Microsurgical anatomy of the dural collar (carotid collar) and rings around the clinoid segment of the internal carotid artery.

To examine the relationship of the clinoid segment of the internal carotid artery to the structures in the roof of the cavernous sinus and to determine whether this segment is neither intradural nor intracavernous, as recently proposed. The region of the roof of the cavernous sinus was dissected and examined using 3 to 40x magnification and micro-operative techniques. The clinoid segment was located within a collar formed by the dura lining the medial surface of the anterior clinoid process, the posterior surface of the optic strut, and the upper part of the carotid sulcus. The clinoid segment and the collar were defined above by the upper ring formed by the dura extending medially from the upper surface of the anterior clinoid process to surround the artery and below by the lower ring formed by the dura extending medially from the lower surface of the anterior clinoid process. The upper ring was adherent to the wall of the artery, but the lower dural ring was separated from the lower margin of the clinoid segment by a narrow space that admitted venous tributaries of the cavernous sinus, called the clinoid venous plexus. This venous plexus narrowed as the upper ring was approached and became wider at the lower ring, where the plexus communicated with the venous channels of the cavernous sinus. The upper and lower dural rings were best defined along the lateral and anterior margins of the artery, were less distinct medially, and disappeared posteriorly, where the dura forming the upper and lower rings came together. The clinoid segment is intracavernous, being located within a collar of dura in which venous tributaries of the cavernous sinus course. The implications of these findings for surgery are reviewed.

Microsurgical Anatomy of the Dural Collar (Carotid Collar) and Rings around the Clinoid Segment of the Internal Carotid Artery

Microsurgical Anatomy of the Dural Collar (Carotid Collar) and Rings around the Clinoid Segment of the Internal Carotid Artery

Microsurgical Anatomy of the Dural Collar (Carotid Collar) and Rings around the Clinoid Segment of the Internal Carotid Artery

Microsurgical Anatomy of the Dural Collar (Carotid Collar) and Rings around the Clinoid Segment of the Internal Carotid Artery

Microsurgical Anatomy of the Dural Collar (Carotid Collar) and Rings around the Clinoid Segment of the Internal Carotid Artery

Microsurgical Anatomy of the Dural Collar (Carotid Collar) and Rings around the Clinoid Segment of the Internal Carotid Artery

Juxta-dural ring aneurysmの分類と治療法

Surgical treatment of internal carotid artery aneurysms around the carotid siphon is an art that is described elaborately in this paper. The surgical approach to the aneurysms in this region, is as follows: 1) A fronto-temporal approach with the patient in a 45° semi-sitting position to decrease venous pressure. 2) A Dolenc's approach cutting a part of the dura mater of the superior orbital fissure to facilitate removal of the anterior clinoid process and unroofing of the optic canal. 3) Opening of the medial triangle followed by transection of the optic canal dural sheath. Carotid siphon aneurysms can be divided into 3 groups anatomically: aneurysms of the ophthalmic segment (C2), those of the clinoid segment (C3), and those of the horizontal segment (C4). We present 34 cases of aneurysms arising from the C2 or C2/3 segment, 15 cases arising from the C3 or C3/4 segment, and 11 cases arising from the C4 segment. Anatomic localization of the aneurysms was established preoperatively by angiography and three-dimensional CT imaging. Small aneurysms of the ophthalmic segment projecting inferomedially can be clipped using a contralateral approach via the prechiasmatic root.Aneurysms of the ophthalmic segment projecting superiorly can be clipped following resection of the anterior clinoid process. The clinoid process should be resected intradurally with direct visualization of the aneurysms. Straight side-angled clips are suitable for these aneurysms. Carotid cave aneurysms, which include aneurysms of the ophthalmic segment oriented inferomedially and of the clinoid segment projecting postero-medially, can be clipped using curved fenestrated clips via Dolenc's extradural approach. For accurate clipping, opening of the medial triangle and full mobilization of the IC at the clinoid segment and optic nerve by unroofing the optic canal are required.Aneurysms of the horizontal portion are clipped after full exposure of the artery in the cavernous sinus only when the aneurysms are large and symptomatic. We used the fronto-temporal and Dolenc's approaches and applied fenestrated clips to aneurysms oriented postero-medially and straight or oblique clips to aneurysms projecting antero-laterally. Out of 52 aneurysms that underwent surgical clipping, 46 resulted in good post-operative recovery. There were 3 deaths secondary to complications of vasospasm and 3 cases with postoperative visual loss. We highlight the classification of these aneurysms and the surgical techniques we had employed.

The superior wall of the cavernous sinus: a microanatomical study.

The superior wall of the cavernous sinus was studied in 30 specimens obtained from 15 cadaver heads fixed in formalin. Trapezoidal in shape, the superior wall of cavernous sinus is limited laterally by the anterior petroclinoid ligament, medially by the dura of the diaphragma sellae, anteriorly by the endosteal dura of the carotid canal, and posteriorly by the posterior petroclinoid ligament. An interclinoid ligament bisects the wall, dividing it into two triangles: the carotid trigone anteromedially and the oculomotor trigone posterolaterally. Similar to the lateral wall of the cavernous sinus, the superior wall is formed by two layers: a smooth superficial dural layer and a thin, less defined deep layer. In the area of the carotid trigone, both layers separate to wrap the anterior clinoid process. The removal of this process will reveal a "clinoid space" medial to which the internal carotid artery can be identified. This clinoid segment of the artery, still extracavernous, is surrounded by two fibrous rings: a distal ring formed by fibers of the superficial dural layer and a proximal ring related to the deep dural layer. Below the proximal ring, the internal carotid artery becomes intracavernous; above the distal ring, the artery is continuous with its supraclinoid segment. The complex dural anatomy of the superior wall, its fibrous rings, and the clinoid space in relation to a superior surgical approach to the cavernous sinus are discussed.