Injury of the tunica media in fatal rupture of the vertebral artery.

The histologic findings in seven cases of traumatic basal subarachnoid hemorrhage from rupture of a vertebral artery are reported. In all cases, blows to the head or neck resulted in minor injury to the cranial or cervical soft tissues but the ipsilateral intracranial segment of the vertebral artery was the site of a longitudinal transmural tear. In addition to rupture, the arterial wall proximal and distal to the site of rupture showed evidence of distortional injury of the tunica media. These traumatic lesions appeared as patchy anuclear regions of the media with distinctive pallor of smooth muscle staining. We propose that the forces which cause vertebral artery rupture stretch the artery along its long axis, thereby distorting the artery leading to this characteristic histologic change.