Intracranial Fusiform Aneurysms: It's Pathogenesis, Clinical Characteristics and Managements

Abstract

Objective: The objective of this study is to investigate clinical characteristics, management methods and possible causes of intracranial fusiform aneurysm.

Methods: Out of a series of 2,458 intracranial aneurysms treated surgically or endovascularly, 22 patients were identified who had discrete fusiform aneurysms. Clinical presentations, locations, treatment methods and possible causes of these aneurysms were analyzed.

Results: Ten patients of fusiform aneurysm were presented with hemorrhage, 5 patients with dizziness with/without headache, 4 with ischemic neurologic deficit, and 1 with 6th nerve palsy from mass effect of aneurysm. Two aneurysms were discovered incidentally. Seventeen aneurysms were located in the anterior circulation, other five in the posterior circulation. The most frequent site of fusiform aneurysm was a middle cerebral artery. The aneurysms were treated with clip, and/or wrapping in 7, resection with/without extracranial-intracranial (EC-IC) bypass in 6, proximal occlusion with coils with/without EC-IC bypass in 5, EC-IC bypass only in 1 and conservative treatment in 3 patient. We obtained good outcome in 20 out of 22 patients. The possible causes of fusiform aneurysms were regard as dissection in 16, atherosclerosis in 4 and collagen disease or uncertain in 2 cases.

Conclusion: There is a subset of cerebral aneurysms with discrete fusiform morphology. Although the dissection or injury of internal elastic lamina of the cerebral vessel is proposed as the underlying cause for most of fusiform aneurysm, more study about pathogenesis of these lesions is required.

Keywords: Atherosclerosis; Cerebral aneurysms; Collagen disease; Dissection; Fusiform aneurysm; Lamina elastica.

Fig. 1

Drawings show pathogenesis of fusiform aneurysm by dissection. Arrows indicate direction of blood flow. A: Arterial dissection with intramural hemorrhage between the intima and media producing focal narrowing of vessel. B: Arterial dissection with rupture producing extension of blood into subarachnoid space or brain. C: Rupture of a dissection into the arterial lumen producing a distal embolization. D: Expansion of intramural clot leading to vessel occlusion. E: Progress enlargement of dissection both laterally and longitudinally. F: Serpentine channel within dissected thrombotic aneurysm. ( ): number of case(s).

Fig. 2

Example of arterial dissection with intramural hemorrhage producing focal narrowing of vessel (A & B) and rupture producing bleeding into brain (C & D). A: Intraoperative surgical microscopic picture of A2 in a 55 year-old male who received surgery for ruptured Acom aneurysm shows arterial dissection with intramural hemorrhage (marked in asterisk) with narrowing of vessel. B: Schematic drawing for the photograph(A) showing A2 with arterial dissection near partial resected gyrus rectus (arrowhead) and frontal lobe (arrow). C: Cerebral angiogram, lateral view, showing fusiform aneurysm (arrow) at central branch of right middle cerebral artery in 27 year-old male who presented with intracerebral hematoma. D: Histopathological findings of that aneurysm of resection showing focal loss of the internal elastic lamina (arrow) along part of the vessel wall (Elastic stain, original magnification ×100).

Fig. 3

Example of rupture into the true lumen with distal embolization(A & B) and expansion of intramural clot leading to vessel occlusion (C & D). A: Brain magnetic resonance image, T2-weighted axial view, showing a round thrombosed aneurysm surrounding with perilesional edema in 53 year-old female who presented with speech disturbance. B: Cerebral angiogram, A-P view of arterial phase, showing filling of small part of thrombosed aneurysm. This aneurysm was occluded with Guglielmi detachable coils by endovascular method. C: Cerebral angiogram, oblique view of arterial phase, showing abrupt occlusion of middle cerebral artery branch (arrow) in 42 year-old female who presented with a subarachnoid hemorrhage. D: Histopathologic findings of aneurysm of resection showing an organized thrombus, irregularly thickened intima (asterisk), and a fragmented or degenerated internal elastic lamina (arrows) along the vessel wall. There was no evidence of atheromatous plaque (Elastic stain, original magnification ×40).

Fig. 4

Example of progress enlargement of dissection both laterally and longitudinally (A, B and C) and serpentine channel within dissected thrombotic aneurysm (D, E, F, and G). A: Cerebral angiogram, anterior-posterior (A-P) view of arterial phase, showing fusiform dilated vessels at left M3 in a 38 year-old male who presented with SAH. B: Postoperative angiogram, A-P view of arterial phase, showing disappearance of previous fusiform aneurysm. C: Histopathologic findings of aneurysm showing disconnected internal elastic lamina (arrows) along the vessel wall. (Elastic stain, original magnification ×40). D: Axial view of enhanced brain computed tomography showing serpentine channel within thrombosed aneurysm(arrow) at left sylvian fissure in 68 year-old male who presented with dizziness. E: Three dimensional cerebral angiogram showing fusiform aneurysm at left M2. The aneurysm was resected followed by a superficial temporal artery-middle cerebral artery anastomosis. F & G: Postoperative internal (F) and external carotid (G) angiogram, lateral views of arterial phase, showing disappearance of previous aneurysm and filling of blood to distal M3 through superficial temporal artery.

Fig. 5

Example of pathogenesis of fusiform aneurysm by atherosclerosis (A) and by collagen disease or unknown cause (B). A: Oblique view of right vertebral artery (VA) angiogram showing a fusiform aneurysm of VA at proximal to posterior inferior cerebellar artery in 54 year-old male who presented with right abducens nerve palsy. This aneurysm was treated with occlusion of right VA and the aneurysm with Guglielmi detachable coils by endovascular method. B: Oblique view of cerebral angiogram showing a fusiform aneurysm at bifurcation of right middle cerebral artery in 37 year-old female who complained of headache. This aneurysm was treated with clipping of aneurysm followed by wrapping with periosteum.