PMC8769483_01
Case 1. (A) The initial CT scan (inset) and 3D CTA showed diffuse SAH predominantly in the right cerebellomedullary cistern and no bleeding source, respectively. (B and C) Selective angiography of the right VA, anteroposterior (B) and lateral views (C), showed no lesions. (D and E) 3D rotational angiography, mild left anterior oblique view (D) and lateral view from the left (E), showed a tiny sphere (arrow) on an aberrant tortuous artery. It arose from the proximal part of the PICA (curved arrow), ran medial and parallel to the VA, and merged into the distal part of the VA (arrowhead). Insets show enlarged images of the lesion. PICA: posterior inferior cerebellar artery, SAH: subarachnoid hemorrhage, VA: vertebral artery.
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F1
A bleeding source in the vertebrobasilar system was suspected, however, 3D CTA failed to show a bleeding source (Fig. 1A). On anteroposterior and lateral digital subtraction images, there was no evidence of vascular lesions (Fig. 1B and 1C). However, a 3D rotational image revealed a 2-mm diameter sphere on an aberrant tortuous artery that arose from the proximal part of the PICA (anterior medullary segment); it ran just medial and parallel to the VA and merged into the distal part of the VA (Fig. 1D and 1E).
Case 1. (A) Intraoperative view. The aberrant artery medial to the VA was tortuous and atherosclerotic; the rostral part was embedded in a clot (arrow). The caudal part showed an unruptured bulge (arrowhead). The inset is a corresponding 3D rotational angiography image; a part of the clot is opacified (arrow). (B) The lesion was trapped with aneurysm clips and removed. A cavity left in the clot at the site where the removed artery had been attached (arrow) suggested rupture at the rostral part that appeared as an aneurysm on the angiogram. (C) Microscopic findings on the affected artery (Elastica-van Gieson stain, magnification x100). Note thickening of the intima by collagen fibers (asterisk) and fragmentation of the internal elastic lamina (arrow). (D) Microscopic findings on the clot (hematoxylin-eosin stain, magnification x20). A fibrotic thickened layer (asterisk) encapsulated a thrombus (double asterisks). The inset shows absence of the internal elastic lamina and angiogenesis in the thrombus (Elastica-van Gieson stain, magnification x100.). VA: vertebral artery.
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F2
We extended a lateral suboccipital craniotomy to the foramen magnum and traced the aberrant artery from its origin at the proximal part of the PICA to its distal tortuous and atherosclerotic part that was partly embedded in a clot (Fig. 2A). The tortuous part was trapped and removed (Fig. 2B); detachment from the clot was easy; however, several perforating arteries supplying the medulla oblongata had to be sacrificed. The histological diagnosis was dissecting aneurysm on the affected artery (Fig. 2C) associated with a false aneurysm in the clot (Fig. 2D).
PMC8769483_02
Case 2. (A) The initial CT scan (inset) and 3D CTA showed SAH limited to the left ambient cistern and communicating segment carotid aneurysms on both sides, respectively. There was no bleeding source in the vertebrobasilar system. (B and C) Selective angiography of the left VA (B, anteroposterior; C, lateral views) revealed an engorged vasculature adjacent to the VA (arrows). (D) 3D rotational angiogram showing an irregular sphere (arrow) on an aberrant artery connecting the distal part of the PICA and the distal part of the AICA. The arrowhead and the curved arrow point to the junction with the PICA and the AICA, respectively. (E) 3D rotational angiogram adjusted for the working angle of the endovascular procedure. Arrow points to the lesion to be treated. (F) Introduction of a microcatheter into the aberrant artery through the PICA. The arrow and arrowheads point to the lesion to be treated and to the microcatheter, respectively. (G) After the selective delivery of detachable coils and n-butyl cyanoacrylate solution, the lesion and the aberrant parent artery were completely occluded. AICA: anterior inferior cerebellar artery, CT: computed tomography, PICA: posterior inferior cerebellar artery, SAH: subarachnoid hemorrhage, VA: vertebral artery.
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F3
There were no apparent lesions in the vertebrobasilar system (Fig. 3A). Left vertebral anteroposterior and lateral angiograms showed an engorged vasculature adjacent to the VA in the arterial phase (Fig. 3B and 3C). On 3D rotational images, the lesion (maximum diameter 4.5 mm) arose from an aberrant artery between the distal part of the PICA (telovelotonsilar segment) and the distal part of the AICA (flocculopeduncular segment) (Fig. 3D). Then a small amount of a 17% n-butyl cyanoacrylate/lipiodol mixture was slowly injected (Fig. 3E and 3F). We confirmed complete occlusion of the lesion and patency of the trunk of the PICA and the AICA (Fig. 3G).