Basilar Artery Trunk Aneurysm: Giant Transitional Aneurysm, Mass Effect, Balloon Test Occlusion, Occlusion of Both Vertebral Arteries with Relief of Mass Effect and Good Outcome

Abstract

A giant basilar trunk transitional aneurysm was treated using deconstructive techniques after confirming clinical tolerance to bilateral vertebral artery (VA) balloon test occlusion. A 38-year-old male presented with a history of chronic headaches, diplopia, right facial hypoesthesia, and progressive ataxia with repeated falls during the last eight months. CT and MRI revealed a giant basilar artery aneurysm with critical compression of the brainstem. Diagnostic cerebral angiography confirmed the presence of a right posterior communicating artery (PcomA) connecting the right internal carotid artery (ICA) to the right posterior cerebral artery (PCA), and the absence of a left PcomA. In the first-stage interventional procedure, the patient underwent bilateral VA balloon test occlusion (BTO) with hypotensive challenge (controlled hypotension 80 mmHg of mean arterial pressure vs. baseline 100 mmHg). He remained clinically stable despite dizziness. Following the BTO, the right VA was occluded using detachable coils placed at the distal VA immediately proximal to the origin of the aneurysm. In the second-stage interventional procedure, performed one month later, the left VA was occluded immediately distal to the origin of the left posterior inferior cerebellar artery (PICA). After the procedure, the patient was neurologically stable when in a flat position, but developed dizziness and nausea when semi-sitting and after sudden positional changes. He was hospitalized in the intensive care unit for hemodynamic management (maintaining controlled hypertension/normotension) and received anticoagulation. At 6-month follow-up, he showed complete clinical recovery. MRI at 1-year follow-up showed remodeling of the basilar trunk and complete resolution of the mass effect on the brainstem. In the flow-diverter stent era, this case reaffirms the validity and efficacy of deconstructive techniques in the management of selected cases of basilar trunk aneurysms.