Evolution from an Infundibulum of the Posterior Communicating Artery to a Saccular Aneurysm

Introduction An infrequent case of a de novo aneurysm formation originating from an infundibulum at the origin of the posterior communicating artery (PcomA) is presented. The aneurysm developed within 7 years in a patient who initially presented with subarachnoid hemorrhage (SAH) from a saccular aneurysm of the vertebral artery. Case summary A 43-year-old female patient was admitted to our hospital on 16th June 2000 after an acute onset of massive occipital headache. A computed tomography (CT) scan showed a subarachnoid hemorrhage (SAH) around the brainstem and 4-vessel angiography revealed an aneurysm originating from the V4 segment of the right vertebral artery (VA) as the cause of the S AH. A small aneurysm at the basilar artery (BA)/superior cerebellar artery (SCA) bifurcation was also found. Injection of the left internal carotid artery (ICA) showed a diffuse enlargement at the origin of the left P comA, which at this time was considered to be a so-called infundibulum. The VA aneurysm was treated by coil occlusion. Follow-up digital subtraction angiography (DSA) in 2005 showed a de novo aneurysm formation at the VA junction, again treated by coil occlusion. The P comA infundibulum at the left ICA was not examined. Followup angiography performed in 2007 revealed a saccular de novo aneurysm of the left ICA arising from the origin of the left P comA with a maximum diameter of 12 mm. Coil occlusion of the P comA aneurysm was subsequently carried out. Conclusion Infundibular widening of cerebral arteries can develop into true aneurysms. Mid-term and long-term follow- up MRI (e.g., in yearly intervals) is advised for infundibula with a diameter of 3 mm or more. In patients with other aneurysm(s), with a documented de novo aneurysm formation or with a familial occurrence of aneurysms, the risk of evolution of an infundibulum to a saccular aneurysm may be increased and follow-up should be even more stringent.