Traumatic rupture involving the isthmus of the descending thoracic aorta is a rarely treated injury in vehicular accident victims. A possible long-term complication of prosthetic replacement of the damaged aortic segment is false aneurysm. This report describes a case of sudden-onset acute paraplegia resulting from thrombosis of a false aneurysm associated with a prosthesis placed 10 years earlier for repair of traumatic rupture of the aortic isthmus.