Massive intracranial bleeding due to the rupture of a rare spontaneous pseudoaneurysm of the middle cerebral artery in a pediatric patient: case report with clinical, radiological, and pathologic findings.

Intracranial pseudoaneurysm (IPA) is a rare but likely underdiagnosed cause of intracranial hemorrhage, which accounts for just 1-6% of all intracranial aneurysms. Spontaneous IPAs are exceptionally rare, and their etiology and features are not well defined. Herein, we report a case of a pediatric patient who died from massive intracranial bleeding due to the rupture of a spontaneous IPA after undergoing multiple radiological studies and neurosurgical operations. At the postmortem examination of the brain, a giant size pseudoaneurysm of the right middle cerebral artery was observed. Microscopic examination demonstrated variable wall thickness and dense fibrosis focally in the vessel wall with disruption of the media structure together with a loss and fragmentation of the elastic laminae, loss of organization of smooth muscle cells in the media, and multifocal areas of hemorrhage throughout the vessel wall, as well as direct evidence of wall dissection. Since IPAs without any traumatic or infective history are extremely uncommon, further pathologic studies should be performed to clarify spontaneous pseudoaneurysm etiology.