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CT and MR Imaging Findings and Their Implications in the Follow-up of Patients with Intracranial Aneurysms Treated with Endosaccular Occlusion with Onyx

Isil Saatcia, H. Saruhan Cekirgea, Elisa F. M. Ciceric, Michel E. Mawadd, A. Gulsun Pamukb and Aytekin Besima

a Departments of Radiology; Hacettepe University Hospital, Ankara, Turkey
b Anesthesiology and Reanimation; Hacettepe University Hospital, Ankara, Turkey
c Instituto Neurologico C. Besta, Milan, Italy
d Department of Radiology, Methodist Hospital, Baylor College of Medicine, Houston, TX



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  		FIG 1. A, Pretreatment angiogram demonstrates partially thrombosed giant right ICA aneurysm.

B, Immediate posttreatment angiogram shows obliteration of the aneurysm sac with minimal filling, if any, at the neck.

C, Follow-up angiogram reveals regrowth at the neck of the aneurysm.

D, Control angiogram after retreatment with the stent and the polymer shows complete obliteration of the aneurysm.

E, Pretreatment contrast-enhanced CT image demonstrates partially thrombosed giant aneurysm with the patent portion of the aneurysm enhancing (arrow). Note the calcification at the aneurysm wall.

F and G, Nonenhanced CT images obtained after initial treatment with parenchyma (F) and bone (G) settings. Attenuating streak artifact hinders the evaluation of the parenchyma. With the bone setting, the attenuating cast of the polymer is seen extending beyond the patent portion; this finding indicates the extension of the material into the thrombus, though it does not completely fill the sac.

H and I, Corresponding T1-weighted images before (H) and after (I) treatment. The images differ in regard to the loss of pulsation artifact (arrows) and the increased hypointensity in the occluded nonthrombosed portion of the aneurysm after treatment.

J–M, Fluid-attenuated inversion recovery images (J, K) and T2-weighted turbo spin-echo images (L, M) demonstrate disappearance of the pulsation artifact (arrows). J and L were obtained before treatment, and K and M, after treatment. The hyperintense interface between the thrombosed portion and the lumen of the patent aneurysm appears thinner, possibly because of the absence of flow and consequent turbulence after treatment. Otherwise, the polymer itself does not create any signal intensity. No change in mass effect and no edema are observed after treatment.



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  		FIG 2. A, Lateral left internal carotid angiogram reveals partial recanalization of the giant left ICA aneurysm that had been initially treated with GDC occlusion.

B, Left internal carotid right oblique angiogram after polymer treatment shows that the regrowth at the neck is completely occluded.

C and D, Axial T2-weighted turbo spin-echo MR images before (C) and after (D) polymer treatment. The entire aneurysm sac is hypointense after being filled; this finding includes the hypointense patent regrowth (arrowhead) and the thrombosed portion containing the GDC (arrows). The signal intensity change in the thrombosed portion may suggest penetration of the polymer into the coil mass and thrombus.



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  		FIG 3. A and B, Right internal carotid angiograms obtained before (A) and after (B) treatment. Images show that the partially thrombosed giant right ICA aneurysm is almost completely occluded; it has a small residual neck.

C, Time-of-flight MRA successfully demonstrates the neck residuum (arrow). Note the slight hyperintensity due to thrombus in the region of giant aneurysm (arrowhead).

D, Pretreatment nonenhanced CT image shows the partially thrombosed giant aneurysm with surrounding edema and mass effect. Arrows indicate the thrombosed portion.

E, Posttreatment CT image (bone settings) shows that the attenuating cast of the polymer fills the aneurysm sac, except for the thrombosed portion.

F–J, Axial MR images through the same level shows the hypointensity of the aneurysm lumen becomes more prominent. The hypointensity extends into the isointense or hyperintense thrombosed portion after treatment; this may indicate the insinuation of the polymer into the thrombus in the sac. The edema and mass effect of the aneurysm persist but do not increase after treatment.

F, Pretreatment T1-weighted image. Note the pulsation artifact with the same caliber as the patent portion (arrows).

G, Posttreatment T1-weighted image.

H, Pretreatment fluid-attenuated inversion recovery image.

I, Posttreatment proton density–weighted image. The artifact disappears on this corresponding image.

J, Posttreatment T2-weighted turbo spin-echo image.




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  		FIG 4. A and B, Pre- and posttreatment angiograms demonstrating large ICA aneurysm occluded completely

C–J, Corresponding pre- and posttreatment T1-weighted (C, D), fluid-attenuated inversion recovery (E, F), turbo spin-echo (G, H), and GRE (I, J) T2-weighted MR images. On the pretreatment images, the left ICA aneurysm shows increased signal intensity due to slow flow (arrow, C, E, G, I). After it was filled with the polymer, the aneurysm appears homogeneously hypointense; the appearance resembles the signal void of a patent aneurysm.



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  		FIG 5. A, Pretreatment angiogram demonstrates the left ICA aneurysm.

B, Phase-contrast MRA obtained after treatment shows occlusion of the aneurysm with no compromise of the parent artery. The polymer does not create any artifact that hinders the application of MRA.

C–E, Corresponding pretreatment T2-weighted turbo spin-echo (C), posttreatment T2-weighted turbo spin-echo (D) and GRE (E) MR images show the hypointense aneurysm. It has an identical appearance before and after treatment that is not possible to appreciate if the aneurysm is patent.



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  		FIG 6. MR imaging appearances of the aneurysms. Graph shows the distribution according to aneurysm size.



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  		FIG 7. A and B, Post-treatment subtracted (A) and nonsubtracted (B) selective angiograms of the right ICA show complete occlusion of the aneurysm. A dense cast of the polymer fills the aneurysm. The parent artery is patent.

C and D, Time-of-flight (C) and phase-contrast (D) MRAs show complete occlusion of the giant aneurysm. The parent artery is patent but markedly narrowed (arrows) due to the presence of the stent, which results in a signal intensity loss.





Copyright © 2008 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X