A patient with ankylosing spondylitis sustained C3-C4 vertebral subluxation and C4-C5 myelopathy after a hyperextension trauma. Autopsy showed that several segments below the main cervical cord lesion at the fractured site, there was a second spinal cord lesion at the T1 vertebral level with no corresponding local bony or ligamentous damage. The thoracic cord lesion was probably secondary to traction of the upper thoracic cord, where the blood supply is poor, in a narrow and rigid spinal canal at the moment of extreme hyperextension.