Vascular lesions in the CS arise within the IJV or carotid artery. PCOM aneurysms have notoriously high recurrence rates following endosaccular coiling. Those incorporating the ophthalmic may be unique, but even that is not the same as, say, treating a choroidal aneurysm. The superior hypophyseal arteries arise from the medial or inferomedial part of the artery, notably supplying the hypophysis and, potentially, portions of the optic apparatus. Important carotid artery lesions include atherosclerosis, dissection with or without pseudoaneurysm, and fibromuscular dysplasia (FMD). Some advocate incising the orbitofrontal dural fold at the level of the sphenoid ridge to avoid cranial nerve injury coursing through the superior orbital fissure. At the distal horizontal petrous segment, before the artery heads superiorely into the lacerum (or transitional) segment, it gives off the mandibulovidian artery, which courses anteriorly through the vidian canal. The 3D-DSA image is particularly instructive for those who look to underlying ICA dysplasia as a necessary pre-condition for aneurysm growth. In view of this, the definition of “transitional segment” is conceptual rather than anatomic — it is that segment where the location of an aneurysm in regard to the dural rings is uncertain. Some additional aid, such as intraoperative angiography or microscope-based indocyanine green (ICG) video angiography could be used to confirm total obliteration of the aneurysm sac. Chapter 367 Intracranial Internal Carotid Artery Aneurysms 22/12/2015 2. How to spot one — an aneurysm projecting, Tired yet? Four cases of traumatic aneurysm of the internal carotid artery are presented and the available literature is reviewed. Another example of likely cave aneuyrsm below. CHAPTER 367Intracranial Internal Carotid Artery Aneurysms Amir R. Dehdashti, M. Christopher Wallace Saccular aneurysms of the internal carotid artery (ICA) trunk and posterior communicating segment represent about 30% to 50% of all intracranial aneurysms. This uncertainly mirrors the underlying trans-segmental nature of many aneurysms found in the area. Many seem to be either asymptomatic or clinically benign, generating much harm in terms of patient anxiety but little beyond that. This system makes the most physiologic sense, and conceptualizes many variants of the ICA and its branches, but it was not designed to facilitate surgical dissections or emerging endovascular methods. If the lesion is in the nasopharyngeal CS, it displaces the PPS fat anteriorly and lifts the styloid process anterolaterally. Purple arrow demonstrating a small mandibulovidian artery. Notice branches of the MHT (purple arrows) which remain open, and are now visible after the aneurysm has disappeared. In practice, the anatomy of Cavernous Segment is dependent on size and morphology of the cavernous sinus, which has a variable and complex anatomy, both in terms of size and compartmentalization. 67-10). Stereo 3D-DSA images of another ugly, dysplastic ophthalmic-hypophyseal one. The next major branch of the ICA is the posterior communicating artery, home to particularly notorious PCOM aneurysms, which seem to rupture with increased frequency for given size, when compared to other aneurysms of the ICA (ISUIA data). The famed artery of Bernasconi-Cassinari comes from there also. In Diagnostic Imaging: Head and Neck (Third Edition), 2017. For example, An entirely different approach was taken by the great Lasjaunias who, together with Santoyo-Vazquez, subdivided the ICA based on, Segment boundaries were defined by intracranial ICA branches, such as, Much surgical work was done to address the complex anatomy of the ICA surrounding the region of the anterior clinoid process, including the transitional segment between the cavernous and intradual ICA, and the various ophthalmic segment aneurysms. With Dr. Rhoton’s kind permission, the following figures are re-e-produced: Another superb source of expert information, freely available online, is the Barrow Quarterly, which ran through 2008, and was overseen by the great M. Spetzler. This transition is critical, since aneurysms past the “distal dural ring” are located in the subarachnoid space, and their rupture leads to subarachnoid hemorrhage. Transitional aneurysms are various — saccular, fusiform, small, large, etc. Classically, PCOM aneurysms arise just distal to PCOM ostium, from the posterolateral ICA wall, and initially projects posterolaterally. (B) Postoperative left internal carotid artery angiogram showing left internal carotid artery aneurysm filled with coils (arrow). Injection of the ICA or, more appropriately CCA, does not necessarily visualize the entire ipsilateral cavernous sinus, particularly when its main cerebral tributary — the superficial Sylvian venous system — is underdeveloped. Three petrous segment aneuyrsms, all extending into the lacerum subsegment, but not distal to the petrolingual ligament, as landmarked by the horizontal plane of the temporal bone (white arrows). The aetiology is unknown, though some patients prove to have connective tissue disorder. When seeing a medially-projecting cavernous aneurysm, CT is mandatory. As an example, see pre- and post- AVM resection angiograms of this patient, where the cavernous segment is perfectly delineated as a region or relative vascular constriction (left image, yellow arrow), whereas the subsequent study the same area (red arrow) actually marks a subtle change towards relative dilatation. The classic, superiorly-pointing one arises just distal to the ophthalmic ositum, or incorporating the initial, cisternal portion of the ophthalmic artery into its base. Petrous segment ICA aneurysms are rare, usually asymptomatic, and, hence, typically incidentally detected on imaging for other indications.12 Occasionally, they cause pulsatile tinnitus, cranial neuropathies, or Horner syndrome.12 On CT, petrous segment ICA aneurysms manifest as well-defined lytic lesions with variable expansion of the anterior petrous apex. What is certain is that nontraumatic cavernous aneurysms are usually fusiform, and have a strong female predominance. This operation involves both an intracranial carotid artery approach and a cervical carotid artery exposure for proximal arterial control of the vessel. IJV thrombophlebitis mimics neck abscess clinically and is easily diagnosed because of the tubular luminal clot and surrounding soft tissue inflammatory changes. This happens somewhere along the distal vertical /ascending cavernous subsegment. This is a lateral left ICA injection in a young epileptic patient status post craniotomy (blue arrow) and subdural strip placement (purple arrow) for invasive EEG monitoring (study done as part of Wada evaluation). If the transient occlusion produces no new neurologic deficits, and if adequate collateral flow exists, occlusion of the ICA can be considered. Visual loss from optic tract compression is rare, and cranial neuropathies other than oculomotor nerve dysfunction do not occur. Blister aneurysms, infrequent, but as such often encountered at this segment, re probably dissecting in nature. At the same time, more reliable endovascular techniques were emerging with introduction of the GDC. Repeat angiography at the 3-month follow-up examination revealed a decrease in size of the aneurysm. Aneurysms of the transitional segment are heterogeneous in all respects. One more…  Now did the ophthalmic ostium get there? Notice also how the ophthalmic stays open with what now looks like a kind of “infundibulum”. The anterior clinoid process and optic strut interfere with exposure and eventual surgical clipping and therefore need to be removed (Fig. The entire carotid artery segment is dysplastic, with what appears as a separate “ophthalmic” segment aneurysm (red arrows) . A somewhat special type is one which arises medially from the ICA at the level of the ophthalmic — as it may in fact be a very proximal superior hypophyseal aneurysm, if such an artery happens to have a proximal origin. Its relationship to the superior hypophyeal arteries is unclear. Medially-projecting transitional segment aneurysms are a special category, since they frequently fall under the distinct rubric of “carotid cave” aneurysms. There is intrinsic angiographic uncertanty about location of the proximal and distal dural rings, with which one must become comfortable. Aneurysms of the petrous segment seem to come in two types — post-traumatic and “other.”  Post-traumatic (not aneurysms but pseudoaneurysms) are usually created by skull base fractures involving the temporal bone, with secondary petrous segment tear/dissection/pseudoaneurysm formation. Publications that reported coexistence of internal carotid artery stenosis with intracranial aneurysm, detected by any modality of imaging, was included in the current study. They are below the distal dural ring, and yet INTRADURAL, and thus potentially more dangeous. The course of the anterior choroidal artery is also confirmed as well as all the branching arteries in the vicinity of the aneurysm. 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