[Dissection of the internal carotid artery].

Closed injury of the internal carotid artery is rare, as it represents only 4% of all the lesions affecting the carotid system. Diagnosis of this injury is difficult, the first signs often being missed as they usually occur in severely injured patients, with the neurological signs appearing later. The death rate remains high, and the sequelae very heavy. After a road traffic accident, three patients, all drivers wearing their seat-belts, presented with bone and/or abdominal lesions, a head injury and a left anterolateral flail chest. All three cases showed an unilateral mydriasis; the variations in their conscious levels led to further neurological investigations. The diagnosis was suggested in one patient by computerized axial tomography, and confirmed in all three by carotid arteriography. The results were excellent when early surgery could be performed (2 cases). However, in the absence of surgery, carotid dissection could only be a major contributing factor for the cerebral oedema associated with the previous hemispheric contusion. The mechanism of these carotid injuries would appear to involve rotation and extension or flexion movements of the neck, crushing the internal carotid artery against the transverse processes of the cervical vertebrae or the mandible: a possible part played by the seat-belt would explain the frequent association of the injury with chest trauma.