Aneurysm saccular

Aneurysms of the posterior circulation account for about 15% of all intracranial aneurysms saccular aneurysms and those of the basilar tip are the most frequent accounting for 5%-8% of all intracranial aneurysms. Ruptured aneurysms in the posterior circulation have a worse prognosis than patients with a ruptured aneurysm in another location (Schievink et al. 1995) and early rerupture occurs more often in this location. Despite improvement in microsurgi-cal therapy, clipping for posterior circulation aneurysms remains challenging. The main problems are the deep location, the presence of many eloquent... 

Primary intracerebral hemorrhage is more common than subarachnoid hemorrhage, and its incidence increases with age (see Fig. 1.1). It is more frequent in Southeast Asian, Japanese and Chinese populations than in whites. The most common causes are intracranial small vessel disease, which is associated with hypertension, cerebral amyloid angiopathy and intracranial vascular malformations (Sutherland and Auer 2006). Rarer causes include saccular aneurysms, hemostatic defects, particularly those induced by anticoagulation or therapeutic thrombolysis, antiplatelet drugs, infective endocarditis, cerebral vasculitis and recreational drug use (Neiman et al. 2000 O Connor et al. 2005). 

Intracranial aneurysms are not congenital but develop over the course of life. Approximately 10% of aneurysms are familial, and candidate genes identified thus far include those coding for the extracellular matrix. Saccular aneurysms tend to occur at branching points on the circle of Willis and proximal cerebral arteries approximately 40% on the anterior communicating artery complex, 30% on the posterior communicating artery or distal internal carotid artery, 20% on the middle cerebral artery and 10% in the posterior... 

Approximately 10% of untreated saccular aneurysms rebleed within hours and another 30% within a few weeks (Brilstra et al. 2002). Subsequently, the rebleeding rate is approximately 2-3% per aimum. Deterioration is usually sudden, with reduced conscious level or fixed dilatation of the pupils in ventilated patients. 

Non-traumatic subarachnoid hemorrhages are usually due to rupture of a saccular aneurysm, most often located at a branch of a major artery or the circle of Willis. Their source is radiographically apparent. 

Fig. 4.16 (a) Axial CTA source images demonstrate a right middle cerebral artery saccular aneurysm, (b) Axial and coronal MIP, and volume-rendered image confirm aneurysm at the right middle cerebral artery... 

Routh WD, Keller FS, Gross GM (1990) Transcatheter thrombosis of a leaking saccular aneurysm of the main renal artery with preservation of renal blood flow. AJR Am J Roentgenol 154 1097-1099... 

Guglielmi G, Vinuela F, Dion J, Duckwiler G (1991) Electrothrombosis of saccular aneurysms via endovascular approach. Part 2 Preliminary clinical experience [see comment], J Neurosurg 75 8-14... 

Rao VR, Mandalam RK, Joseph S, et al. (1990) Embolization of large saccular aneurysms with Gianturco coils. Radiology 175 407-410... 

Enright T.R., Kanne J.P. (2010) Saccular superior vena cava aneurysm - incidental diagnosis by MDCT. Clin Radiol 65 421-422. 

Saccular aneurysms are berry-like vessel outpouch-ings mostly arising from arterial bifurcations and account for 66%-98% of intracranial aneurysms (Yong-Zhong and van Alphen 1990). The vast majority of aneurysms (85%) are located in the anterior and only 15% are located in the posterior circulation (Kassell and Torner 1983). 

The most plausible pathogenetic theory is that they are acquired due to hemodynamic stress on the relatively unsupported bifurcations of cerebral arteries (Timperman et al. 1995). This is supported by the clinical observation that many patients with an anterior communicating artery (Acorn) aneurysm do have one hypoplastic or absent Al segment and thus an increased hemodynamic stress on the AcomA. Other factors than hemodynamics and structural alterations of the vessel wall contributing to the development of saccular aneurysms may be genetic, infection, trauma, neoplasms, radiation or idiopathic. 

Saccular aneurysms of spinal arteries are rare. The clinical features of spinal SAH are usually associated with those of a transverse spinal cord lesion but may mimic SAH due to an intracranial aneurysm (Mohsenipour et al. 1994, Kocak et al. 2006). 

Brunereau L, Cottier JP, Sonier CB, Medioni B, Bertrand P, Rouleau P, Sirinelli D, Herbreteau D (1999) Prospective evaluation of time-of-flight MR angiography in the follow-up of intracranial saccular aneurysms treated with Guglielmi detachable coils. J Comput Assist Tomogr 23 216-223... 

Van Rooij WJ, Sluzewski M, Menovsky T, Wijnalda D (2003) Coiling of saccular basilar trunk aneurysms. Neuroradiology 45 19-21... 

Weber W, Yousry TA, Felber SR, Henkes H, Nahser HC, Roer N, Kuhne D (2001) Noninvasive follow-up of GDC-treated saccular aneurysms by MR angiography. Fur Radiol 11 1792-1797... 

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