Post-traumatic aneurysmal rupture involving the circle of Willis affected by fibromuscular dysplasia. A case report and literature review.

The fatal rupture of a saccular aneurysm at the junction between the left anterior cerebral artery and anterior communicating artery affected by fibromuscular dysplasia (FMD) is a rare condition. Here is reported the case of a subject involved in a road traffic accident a few minutes before the death, which opened the debate on the real cause of death in a forensic setting. By autopsy, subarachnoid haemorrhage with flooding of the ventricles due to the breached saccular aneurysm of the junction between the left anterior cerebral artery and anterior communicating artery was detected in a subject otherwise presenting FMD affecting the circle of Willis arteries. A spontaneous aneurysmal rupture was excluded on the basis of probabilistic analysis, in the presence of alternative hypotheses that could fully explain the facts. The passenger’s delayed loss of consciousness may be explained as much by a hypertension-linked rupture of the aneurysm triggered by the emotional stress experienced, as by the traumatic shaking/impact of the aneurysm against the bony skull structures, both of them in a subject predisposed to aneurysm frailty due to FMD. Both these hypotheses converged on the described road traffic accident, which was the primal event triggering the chain of events culminating in death. The recognition of anatomical variants, jointly with identification of uncommon diseases at the examination of the brain base arteries in any case of isolated basal subarachnoid haemorrhage, may avoid wrong legal consequences even when the cause of death seems to be obviously of traumatic origin. https://doi.org/10.1016/j.legalmed.2020.101742