Isolated basilar traumatic subarachnoid hemorrhage: an observer's 25 year re-evaluation of the pathogenetic possibilities

Abstract

This paper was inspired by Leadbeatter's recent review [1] on the subject, and consists primarily of a recapitulation of this author's observations in the 25 years since publication of his paper [2] describing three cases of traumatic basilar subarachnoid hemorrhage resulting from direct trauma to the upper lateral neck. Those observations include personal experience and case reports personally communicated or published. Leadbeatter's analysis makes the following three salient points to which the author considers a response to be appropriate: 1. For the ten years following Contostavlos' paper, all traumatic basilar subarachnoid hemorrhages were considered to have resulted exclusively from direct extracranial trauma to the vertebral artery. That belief has since gradually been eroded. 2. The mechanisms of injury and hemorrhage have been inadequately explored and demonstrated due to absence of appropriate and adequate anatomic dissection. 3. Attention has been increasingly turned toward other factors besides direct arterial injury such as indirect mechanisms of injury, hyperextension of head on neck, hemodynamic effects and congenital anomalies of the craniocervical articulation. This author responds to these assertions thus: 1. Traumatic subarachnoid hemorrhages do not have one mechanism only. The lesion described in Contostavlos' paper merely represents one commonly observed syndrome, as supported by the numerous case reports which have followed and also preceded his account. There may have been a tendency to ‘pigeon-hole’ too many cases into that category but this author's personal experience in the past 25 years has shown that ∼50% of traumatic isolated basilar subarachnoid hemorrhage fall into that category (direct trauma to lateral or posterolateral neck). 2. The anatomic location of the injury virtually prevents effective demonstration by dissection, and the possibilities of misleading artefacts incurred during the autopsy are such that many erroneous conclusions are reached by prosectors, as well as many sites of significant trauma remaining undiscovered. Accordingly, empirical factors have to be considered for a diagnosis in most cases. Four diagnostic criteria have been established for a firm conclusion of death due to traumatic basilar subarachnoid hemorrhage. 3. While over half of traumatic basilar subarachnoid hemorrhages involve a completely different site of trauma, and many indirect mechanisms of injury may come into play, the author still considers that in the commonly observed syndrome as described by him in 1971, direct trauma to the vertebral artery is the primary causative factor.