Fibromuscular dysplasia of the basilar artery: an unusual case with medico-legal implications

A 28-year-old male car driver was reported to suddenly loose the control over his vehicle, to hit the right and middle crash barrier, and to be unconscious as the car came to a halt in a position at right angles to the road. The car was hit in its left side by an automobile with high velocity, and the 28-year-old driver died. Examination of the brain revealed a massive isolated basal subarachnoid hemorrhage and a complete tearing of the basilar artery. A macroscopically detectable aneurysm was not found. However, histological examination of the large arteries at the base of the brain showed (i) fibromuscular dysplasia (FMD) mostly involving the basilar artery (ii) with a ruptured micro-aneurysm in its upper third part. The observations of the eye witnesses that the driver initially lost control over his car were judged in favour of the accused to be due to that rupture of the micro-aneurysm, while complete transverse tearing of the basilar artery occurred during the car crash due to hyperextension and rotation of his neck. Intracranial FMD is a rare cause in the differential diagnosis of isolated basal subarachnoid hemorrhage. The medico-legal implications of this entity are described in the presented case.