Ruptured aneurysm at the cortical segment of the distal posterior inferior cerebellar artery associated with hemodynamic stress after basilar artery occlusion

BACKGROUND: A distal posterior inferior cerebellar artery (PICA) de novo aneurysm at the cortical segment after atherosclerotic basilar artery occlusion is extremely rare. Here, we report the case of a ruptured distal PICA de novo aneurysm 8 years after basilar artery occlusion. CASE DESCRIPTION: A 75-year-old man experienced sudden disturbance of consciousness; computed tomography demonstrated cerebellar and subarachnoid hemorrhage due to a ruptured distal PICA aneurysm. Neck clipping of the aneurysm prevented re-rupture initially, and superficial temporal artery-superior cerebellar artery (STA-SCA) bypass was performed 3 months after admission. Postoperative angiography confirmed patency of the bypass, and the patient was discharged without any new neurological deficits. CONCLUSION: This report describes a case of de novo development of a saccular distal PICA aneurysm after atherosclerotic basilar artery occlusion. We believe that increased hemodynamic stress at the PICA might have contributed to the occurrence and rupture of the aneurysm. STA-SCA bypass, introduced in the territory of the cerebellar hemisphere, reduces hemodynamic stress, which would prevent the occurrence of de novo aneurysm and recurrent bleeding.