Pathology

Saccular aneurysms (Fig. 2) are usually located at the vascular bifurcations within the Circle of Willis. At the bifurcation, the aneurysm most commonly originates at the apex. The wall of an aneurysm consists primarily of collagen, with some smooth muscle cells and only isolated fragments of elastic lamina (17,18). At the level of the neck, the IEL almost completely disappears. Furthermore, the intima becomes thickened near the neck, and atheroma is frequently present (19). The endothelial layer is generally preserved along the wall of the entire aneu-rysm. It is thin along the aneurysmal wall and becomes thicker at the aneurysmal neck. Larger aneurysms might contain layers of thrombus and occasionally become partially or completely thrombosed. The vasa vasorum might contain evidence of atherosclerosis and partial occlusion (19). Aneurysms are not uncommonly multiloculated (>1 discrete dome). In an autopsy review of ruptured and unruptured aneurysms, 57% of ruptured aneurysms and 26% of unruptured aneurysms >4 mm in size were found to be multiloculated (20).

Three types of early aneurysmal changes typically found at arterial bifurcations have been described: funnel-shaped dilations, areas of thinning, and microscopic evaginations (21). Funnel-shaped dilations, most commonly appearing at the posterior communicating artery/ internal carotid artery junction, have attenuated walls and a complete loss of the elastic lamina (21,22). Areas of thinning occur at the apex and/or tissue adjacent to the apex. These areas

Figure 2 This intraoperative photograph shows an aneurysm at the middle cerebral artery bifurcation. The distal middle cerebral branches can be seen on each side of the body or fundus of the aneurysm. A secondary bleb (or loculation) is arising from the fundus of this lesion, creating a new dome. The neck of the aneurysm lies at the base of the fundus and can be clearly seen in this image.

Figure 2 This intraoperative photograph shows an aneurysm at the middle cerebral artery bifurcation. The distal middle cerebral branches can be seen on each side of the body or fundus of the aneurysm. A secondary bleb (or loculation) is arising from the fundus of this lesion, creating a new dome. The neck of the aneurysm lies at the base of the fundus and can be clearly seen in this image.

are extremely thin and can be nearly transparent. Microscopic evaginations often involve a medial defect of the apex. Interestingly, these evaginations can incorporate a portion, if not the entirety, of the medial defect, but they generally do not originate from the defect itself (21). At the apex of the aneurysm, the fibrous wall is usually its thinnest and is the site most likely to rupture. In a review of 289 autopsy specimens of patients who died from intracerebral hemorrhage, the site of rupture of the aneurysm was evaluated. In 227 cases, the rupture occurred along the fundus, and only 6 ruptured along the neck (23).

Metabolism Masterclass

Metabolism Masterclass

Are You Sick And Tired Of All The Fat-Burning Tricks And Trends That Just Don’t Deliver? Well, Get Set To Discover The Easy, Safe, Fast, And Permanent Way To Mega-Charge Your Metabolism And Lose Excess Fat Once And For All! This Weight Blasting Method Is Easy AND Natural… And Will Give You The Hot Body And Killer Energy Levels You’ve Been Dreaming Of.

Get My Free Ebook


Post a comment