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Fig 1. A 46-year old woman (patient 4; Table) experienced acute onset of headache. MR imaging and MR angiography showed a right-sided PICA aneurysm without any evidence of intracranial bleeding. In initial DSA (A), a 9- x 5.5-mm sidewall aneurysm was visualized in a tonsillomedullary segment of the right PICA. The artery is narrowed proximally and dilated distally to the aneurysm neck. A balloon occlusion test was performed with indeterminate findings. The aneurysm was treated by endosaccular coiling with parent artery preservation. The initial occlusion grade was incomplete, but after retreatment a complete occlusion was achieved, and it has remained stable during follow-up (Fig 2B).
