Microsurgical Clipping of an Unruptured Basilar Tip Aneurysm with a Posterior Thalamoperforating Artery Mimicking Dome Origin on Preoperative Angiography.

Basilar tip (BT) aneurysms are challenging due to their deep location and proximity to posterior thalamoperforating arteries (PThPAs) and the oculomotor nerve.1-5 Posterior circulation aneurysms have a higher rupture risk than those in the anterior circulation.6 Surgical complexity depends on aneurysm size, projection, and the relationship to the PThPAs, which may not be fully delineated by angiography, despite its gold standard role. Given the severe consequences of perforator occlusion, microsurgical treatment remains an important option in selected patients, offering direct anatomical clarification when perforator involvement is suspected.7-10 We present a BT aneurysm with the angiographic impression that a PThPA arose from the aneurysm dome. A 53-year-old female patient presented with nonspecific headache, dizziness, nausea/vomiting, and mild left ptosis. The aneurysm was identified incidentally during this workup. Computed tomography and cerebral angiography revealed an unruptured superoposteriorly projecting BT aneurysm (5.0 × 4.3 × 4.5 mm), with 3D imaging raising concern that a PThPA arose from the dome, which was felt to make endovascular treatment less suitable. The patient underwent microsurgical clipping via a pterional pretemporal approach with anterior and posterior clinoidectomy. Intraoperative inspection showed that the suspected PThPA did not arise from the dome but draped over it. After full exposure, we applied a fenestrated titanium clip. Postoperative angiography confirmed complete obliteration with an uneventful course. Microsurgical clipping provided durable aneurysm control with direct preservation of the perforator. Although endovascular treatment is the first-line approach for most BT aneurysms, microsurgical clipping can be performed with contemporary microsurgical techniques that increase the exposed area and improve visualization of the PThPAs.8,10 The surgical technique is demonstrated in Video 1.