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AJNR - American Journal of Neuroradiology

A, Gross photograph showing thin membranous tissue at the neck with coil loops that are visible through the membrane.

B, Section of the vertebrobasilar aneurysm stained with H&E (magnification 100x). The photomicrograph shows hypocellular, amorphous tissue in the dome.

C, Section of the aneurysm stained with H&E (magnification 60x). This photomicrograph shows a large area of poorly organized thrombus in the aneurysm dome.

D, Section stained with H&E (magnification 20x). A photomicrograph showing a thin layer of hypocellular tissue covering the neck of aneurysm.

E, Immunofluorescent double stain of the vertebrobasilar aneurysm, with antibodies for SMA (red) and vimentin (green) (magnification 20x; oil). This photomicrograph shows scattered, sparse cells within the aneurysm dome, which are positive for vimentin, but negative for SMA.

F, Stained with Masson trichrome (magnification 60x). It reveals that collagen deposition was absent in the aneurysm.

A, Gross photograph showing a thin, translucent membranous tissue at the neck, through which coils loops are visible.

B, Section of the rabbit aneurysm stained with H&E (magnification 60x). The photomicrograph shows loose, hypocellular, amorphous tissue in the dome.

C, Section stained with H&E (magnification 60x). The photomicrograph illustrates the thin layer of tissue along the entire neck.

D, Masson trichrome stain (magnification 60x). The photomicrograph reveals no collagen deposition within the aneurysm dome’s loose tissue.

E, Immunofluorescent double stain with antibodies for SMA (red) and vimentin (green) (magnification 20x; oil). This photomicrograph reveals that the scattered cells within the aneurysm dome are positive for vimentin and negative for SMA. In addition, the cells lining the thin neovessels were shown to be positive for SMA and vimentin.

A, Gross photograph showing a smooth, thick membrane completely covering the neck. Coil loops are not visible through this membrane.

B, Section of the swine aneurysm stained with H&E (magnification 60x). The photomicrograph shows diffuse, attenuated chronic inflammatory tissue within the aneurysm dome.

C, Stained with H&E (magnification 60x). This photomicrograph shows extensive, attenuated, fibrous tissue within the dome, which is associated with rich neovessels.

D, Section stained with Masson trichrome (magnification 60x). A photomicrograph shows diffuse, attenuated, abundant, collagen fibers within the aneurysm dome.

E, Section stained with H&E (magnification 40x). A photomicrograph of this stained section shows a thick layer of hypercellular tissue along aneurysm neck.

F, Immunofluorescent double stain with antibodies for SMA (red) and vimentin (green) (magnification = 20x; oil). This photomicrograph reveals the attenuated cells at neck of aneurysm are positive for both SMA and vimentin, which indicates classic neointimal formation.