Head injury without loss of consciousness is seldom accompanied by grave complications. We report the case of an 18 year old cyclist who was struck by a car in a minor road traffic accident, suffered minor head injury without loss of consciousness, and died unexpectedly seven weeks later with vomiting and coma. Necropsy revealed an expanding cerebellar infarct and vertebral artery thrombosis, superimposed on an old dissecting intramural haematoma of the right vertebral artery in the atlantoaxial region. Vertebrobasilar occlusion after minor head trauma, hyperextending or rotating neck injury, or neck manipulation is commonest in young people. Occult ligamentous injury to the cervical spine after trauma may be a contributing factor to the pathogenesis of vertebral artery damage after injury to the neck.