PMC8769443_01
(A) Axial T2-weighted magnetic resonance imaging (MRI) on admission demonstrates an extra-axial mass in the right ambient cistern causing marked compression of the right cerebral peduncle. Coronal (B) and sagittal (C) T1-weighted enhanced MRI shows homogeneous peripheral enhancement. Magnetic resonance angiography (D) demonstrates the lesion as an avascular area, and the right posterior cerebral artery is occluded distally. On anteroposterior (E) and lateral (F) left vertebral angiography, the right P2 is shifted medially and inferiorly, elongated, and tenuous; no contrast is visualized in the posterior temporal artery.
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Magnetic resonance imaging (MRI) showed a 30 mm diameter mass in the right ambient cistern compressing the brainstem; the periphery of the lesion exhibited contrast enhancement, and the signal intensity within the mass suggested thrombus (Figs. 1A-1C). The vasculature distal to the right P2 segment was poorly visualized on magnetic resonance angiography (Fig. 1D). Cerebral angiography showed medial and inferior displacement of the main trunk of the right P2 segment (Figs. 1E and 1F).
Intraoperative photograph showing the view after a right posterior transpetrosal approach (asterisk: aneurysm; black arrow: oculomotor nerve; white arrow: P2 main trunk; white arrowhead: proximal posterior temporal artery (PTA); black arrowhead: distal PTA). (A) The right oculomotor nerve and proximal P2 can be seen in the ambient cistern; the giant aneurysm is located distally along the right posterior temporal artery. (B) The distal P2 is coagulated. (C) Intra-aneurysmal thrombus is excised after temporary clip placement. Postoperative contrast-enhanced axial T1-weighted magnetic resonance imaging demonstrates a shrunken residual aneurysm (D) without evidence of cerebral infarction on diffusion-weighted sequences (E).
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PTA; then, the aneurysm wall was incised, the intra-aneurysmal thrombus was removed as much as possible, and a permanent titanium clip was applied to the proximal PTA (Figs. 2A-2C). Postoperative MRI showed a shrunken residual aneurysm (Fig. 2D) and no cerebral infarction (Fig. 2E).