Occipital Artery to Anterior Inferior Cerebellar Artery (AICA) Bypass for Treatment of a Ruptured Proximal AICA-Posterior Inferior Cerebellar Artery Mycotic Aneurysm.

BACKGROUND: Intracranial mycotic aneurysms are uncommon. They can occur due to extravascular extension or intravascular seeding of the vessel wall. They often result in subarachnoid hemorrhage with poor prognosis. We present a rare case of subarachnoid hemorrhage due to vertebral artery dissection with aproximal anterior inferior cerebellar artery (AICA)-posterior inferior cerebellar artery common trunk mycotic aneurysm after an episode of bacterial meningitis.

CASE DESCRIPTION: A 66-year-old male with history of 2 episodes of culture-negative bacterial meningitis presented with a Hunt and Hess grade II, Fisher grade III subarachnoid hemorrhage. Catheter angiography showed a right-sided intracranial vertebral artery (VA) dissection and a fusiform AICA-posterior inferior cerebellar artery trunk aneurysm. The patient underwent an endovascular occlusion of the VA dissecting aneurysm followed by an occipital artery to AICA bypass with trapping of the aneurysm. The patient developed a left-sided numbness and weakness after the coiling procedure due to anteromedian medullary stroke (occlusion of the right anterior spinal artery). The patient's magnetic resonance imaging 3 weeks before the aneurysm rupture and during the second episode of meningitis showed new enhancement of both vertebral arteries with a mild reduction in the right VA caliber. At 6 weeks' follow-up the patient was off the ventilator but had a modified Rankin Scale score of 5.

CONCLUSIONS: Bacterial meningitis can lead to inflammatory injury of the intracranial vessels with resultant aneurysm formation. New enhancement of the vessel wall indicates that patients are at risk of developing mycotic aneurysms; therefore close observation with repeated vascular imaging is necessary.