Aneurysms fusiform

Fusiform aneurysms are dilated, tortuous and elongated arterial segments. The term dolichoectasia describes a giant ectatic vessel of this type of aneurysms. Fusiform aneurysms are characterized by the absence of a defined neck, circumferential involvement of the parent artery and a longish course. The aneurysm can be partially thrombosed. 

Atherosclerosis mainly affects large- and mediumsized arteries. Extracranial manifestations at the carotid bifurcation statistically dominate the intracranial arteries. Besides typical manifestations at the carotid siphon or the vertebrobasilar junction, atherosclerosis is occasionally also found in peripheral intracranial vessel segments. Typical sequelae of atherosclerosis are stenosing plaque formations, ulcerations, dilatations or the evolution of fusiform aneurysms, which can be accompanied by extensive formation of thrombus. 

Fig. 5.20a-d. Subacute thrombus formation in a large fusiforme aneurysm of the basilar artery. Parts of the thrombus are still isoin-tense to brain, while others are moderately hyperintense on spin echo Tl-weighted image (a). Residual flow within the vessel is outlined against thrombus much better on post-contrast Tl-weighted spin echo (c) and post-contrast TOF-MRA (d) than on unenhanced TOF-MRA (b)... 

These materials have an obvious application to fusiform aneurysms, which are difficult to treat using coils or liquid embolics due to migration into the parent vessel. Shape memory polymers can potentially remove this limitation since the device is pre-formed to the aneurysm topography. Metcalf et al (2003) investigated a porous polyurethane shape memory polymer as an embolic device for fusiform aneurysms in an animal model. In this study, thick neointimal formation was found over aneurysm necks after a 12-week period. The porous nature of this material may have encouraged cell infiltration and neointimal growth to seal off the aneurysm from the rest of the vasculature (Metcalfe et al,... 

Lohani, B. (2004) Fusiform middle cerebral artery aneurysm. Journal of Neuroscience, 1,... 

Small, W., Buckley, P. R., Wilson, T., Benett, W. J., Hartman, J., Saloner, D. Maitland, D. (2007) Shape memory polymer stent with expandable foam a new concept for endovascular embolization of fusiform aneurysms. IEEE Transactions on Biomedical Engineering, 54, 1157—1160. 

Phatouros CC, Sasaki TY, Higashida RT,et al. (2000) Stent-supported coil embolization the treatment of fusiform and wide-neck aneurysms and pseudoaneurysms. Neurosurgery 47 107-113... 

AAAs present in three different types or shapes. Fusiform aneurysms, the most typical, are mostly symmetrical bulges that occur around the entire circumference of the aorta. These are sometimes referred to as false aneurysms or pseudoaneurysms, because layers of the wall of the aorta are missing (as opposed to the presence of all three layers in a true aneurysm). An aortic dissection, on the other hand, is when blood penetrates the inner layer of the aortic wall, and flows between the layers, similar to delamination. This typically occurs in the thoracic region of the aorta, but can sometimes occur in the abdominal region. Figure 21.3 shows these various types of aneurysms. 

A transient encephalopathy has been reported after the use of an iodinated contrast medium in a neurointerventional procedure with development of psychomotor agitation, disorientation, and progressive left faciobrachial hemiparesis 30 minutes after successful treatment of a right carotid-ophthalmic fusiform aneurysm [6 ]. A CT scan showed marked cortical enhancement and edema in the right cerebral hemisphere, thought to be due to contrast extravasation after disruption of the blood-brain barrier. Treatment with dexa-methasone and maimitol produced complete recovery. 

Fig. 5.3a-d. Fusiform basilar aneurysm causing massive brain stem compression in a 54-year-old man with hemiparesis and dysarthria. Stent deployment (Leo, Balt) and coiling was performed, 3 month later patient was able to walk... 

Fig. 5.20. Acutely ruptured fusiform posterior cerebral artery aneurysm before and after endovascular treatment. Overlay of 3D vessel anatomy on cross-sectional CT-like images showing extensive SAH...

Fig. 5.23. a,b 3D CTA of bilateral MCA aneurysm and a small vertebral aneurysm, c-e DSA (ap view), aneurysmog-raphy and 3D CTA of a large MCA aneurysm demonstrating that one major MCA branch is originating very close to the neck of the aneurysm. f,g Fusiform MCA aneurysm 3D CTA and DSA match perfectly, h-j Broad-based basilar artery aneurysm encroaching both PI segments demonstrated on 3D CTA as well as on DSA. k-m Ruptured Pcom aneurysm (arrow)... 

Findlay JM, Hao C, Emery D (2002) Non-atherosclerotic fusiform cerebral aneurysms. Can J Neurol Sci 29 41-48 Fiorella D, Albuquerque FC, Deshmukh VR, McDougall CG (2005) Usefulness of the Neuroform stent for the treatment of cerebral aneurysms results at initial (3-6 mo.) follow-up. Neurosurgery 56(6) 1191-1201 discussion 1201-1202... 

Morphologically, there are fusiform aneurysms (synonymous with circumferential) and sacciform aneurysms, which lead only to a partial dilatation of the aortic wall (Isselbacher 2005). The most common examinations for clinical diagnostics of TAA include echocardiography, MDCT, and MRl (Rubin and Kalra 2006). CTA of the aorta provides a clear visualization of the diameter and allows an evaluation of the relative position of the aneurysm to the neighboring anatomic structures (Fig. 23.5). Dystrophic calcifications of thrombi adherent to the aortic wall can sometimes simulate a dissection of the aortic wall. In the case of a suspected leakage of the aneurysm, an additional nonenhanced scan is recommended in order to detect a periaortic hematoma. 

Fig. 40.2 Fusiform acutely ruptured posterior cerebral artery aneurysm before and after parent artery coil occlusion (DSA). Postprocessing of FD-dataset with overlay of 3D-DSA vessel anatomy (displayed in red color) and soft tissue imaging of FD-CT...

Aneurysms can be either saccular or fusiform. Saccular aneurysms are typically spherical in shape and have a small communication or neck arising from the parent vessel (Fig. 8.1). Fusiform implies longitudinal dilatation along the course of the... 

Aneurysm configuration should influence treatment planning. Proximal and distal control should be obtained if the aneurysm itself cannot be occluded. It is typically easier to occlude short necks seen with the saccular form therefore many different treatment options exist. These will be discussed later in the chapter. Fusiform aneurysms may not allow for both proximal and distal control and are often better treated with surgical ligation or reconstruction. 

Higashida RT, Smith W, Gress D, Urwin R, Dowd CF, Balousek PA, Halbach VV (1997) Intravascular stent and endovascular coil placement for a ruptured fusiform aneurysm of the basilar artery. Case report and review of the literature. J Neurosurg 87 944-949... 

Figure 3 Fusiform aneurysm of the pulmonary artery in a patient with Behget s disease.

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