A case is reported of a 52-year-old man who sustained a cervical spine dislocation in a road traffic accident, which was complicated by an initially asymptomatic vertebral arterial thrombosis. Embolism from this thrombosis into the vertebrobasilar territory during the surgical manoeuvers to reduce the dislocation was the cause of a fatal postanaesthetic coma. Such unexpected but life-threatening neurological consequences may be found with trauma of the cervical spine of various intensities. The diagnosis may be made by angiography. However, the usefulness of atraumatic investigations, such as the cervical doppler, and the indications for angiography need to be assessed.