Severe brainstem compression by an unruptured giant vertebral aneurysm – An autopsy case

We describe an autopsy case of sudden unexpected death due to severe brainstem compression by an unruptured giant vertebral aneurysm. A 71-year-old male was found dead in his bedroom. The forensic autopsy revealed no severe trauma leading to his death. On internal examination, a giant intracranial aneurysm (3.4 × 2.6 × 2.7 cm) was observed on the trunk of the right vertebral artery. The aneurysm compressed the right side of the lower one-third of the pons and adjacent medulla oblongata. On sectioning, almost all of the aneurysm lumen was filled with a firm, clearly laminated organized thrombus. There was no evidence of subarachnoid hemorrhage. Histopathological analyses revealed congestion and hypoxic tissue changes in all organs examined. In microscopic sections of the giant vertebral aneurysm, thick fibrotic walls, intimal hyperplasia and organized thrombi in the lumen were found. Lots of intrathrombotic clefts with fresh erythrocytes were also observed. Moreover, Elastica van Gieson staining revealed fragmentation and disruption of the intimal elastic lamina in the aneurysmal wall. Collectively, we considered that some triggers in his daily life, including head rotation, might have caused the rapid onset of respiratory disturbance due to severe brainstem compression by a giant vertebral aneurysm.