Spinal injury following inertial loading of the head and neck (whiplash) is a common sequel of low speed traffic crashes. A variety of non-musculoskeletal injuries have been described in association with injury to the spine following whiplash trauma, including traumatic brain injury, vestibular derangement, and cranial nerve injury, among others. Vascular injuries in the head and neck have, however, only rarely been described. We present the case of a middle-aged male who sustained an ultimately fatal injury that resulted from injury to the internal carotid artery (ICA) and intracerebral vascular structures following a hard braking maneuver, with no direct head- or neck contact with the vehicular interior. Based on this unusual mechanism of injury we reviewed hospital data from the United States nationwide inpatient database (NIS) to assess the frequency of similar injuries reportedly resulting from traffic crashes. The post-mortem examination revealed a left internal carotid artery dissection associated with subarachnoid hemorrhage (SAH). Based on the close temporal association, the absent prior history, and the plausibility of the injury mechanism, the injury was attributed to the braking maneuver. An analysis of NIS data demonstrated that the prevalence of subarachnoid hemorrhage is significantly higher when there is a traumatic etiology, and higher yet when the trauma is a traffic crash (odds ratio 3.3 and 4.3, respectively). The presented case, together with the hospital inpatient data analysis, indicate that although SAH in combination with ICA dissection is relatively rare, it is substantially more probable following a traffic crash. In a clinical or forensic setting the inference that magnitude of a trauma was low should not serve as a basis for either excluding a cervical artery dissection from a differential diagnosis, or for excluding the trauma as a cause of a diagnosed dissection. This case report illustrates a rare fatal outcome of inertial load to the head and neck induced by a sudden braking event in a commonly experienced non-collision traffic incident. The likely mechanism of injury resulted from interaction between the occupant and the 3-point seat belt. These findings indicate that ICA dissections are substantially more likely to be associated with SAH following head and neck trauma, regardless of the magnitude of the traumatic event or whether an impact was involved.
