Acute traumatic paralysis may also be the indirect consequence of a vascular mechanism, mainly through infarction from fibrocartilaginous emboli arising in an intervertebral disc that has ruptured into a radicular artery or vein of the cord. Or a traumatic dissecting aneurysm of the aorta may occlude the segmental arteries of the spinal cord, as in the cases reported by Weisman and Adams and by Kneisley. One striking variant of this type of vascular injury is infarction of the upper cervical cord, resulting in hemi-, tri-, or tetraplegia, from dissection of one or both vertebral arteries and occlusion of their tributary anterior spinal arteries at the cervicomedullary junction.
Vertebral fracture and dislocation An analysis from a long-past but still instructive era, by jefferson of 2,000 cases of spinal injury collected from the medical literature up to 1927 showed that most vertebral injuries occurred at the levels of the first and second cervical, fourth to sixth cervical, and eleventh thoracic to second lumbar vertebrae. Industrial accidents most often involved the thoracolumbar vertebrae. Impact to the head with the neck flexed or sharply retroflexed, as mentioned earlier, was the main cause of injuries to the cervical region. These are not only the most mobile portions of the vertebral column but also the regions in which the cervical and lumbar enlargements of the cord greatly reduce the space between neural and bony structures. The thoracic cord is relatively small and its spinal canal is capacious; additional protection is provided by the high and overlapping articular facets, making dislocation difficult, and by limitations in anterior displacement of vertebral bodies imposed by the thoracic cage.
Several configurations of vertebral fractures are common enough that they are designated by eponyms or descriptive terms. The knowledgeable clinician has some familiarity with them. They are summarized in Table 42-1. They include the Jefferson fracture, hangman’s fracture, the Chance fracture, atlanto-axial (C1-C2) and the more common atlanto-occipital fracture–dislocation, including fracture of the dens of C2. Regarding hangman’s fracture, contrary to the popular notion, most penal hangings do not cause vertebral bony disruption and death is instead by strangulation; a more common mechanism for hangman’s fracture is an elderly person who falls and strikes the chin, causing hyperextension of the neck. The majority of fatal cases of cervical spine injury are from fracture–dislocations of the upper cervical spine (C1 to C3 vertebrae, thus encompassing atlanto-occipital and atlanto-axis dislocations with sudden respiratory paralysis).
Acute Evaluation of the Spine-Injured Patient
The level of the spinal cord damage and, by implication, the level of disruption of the spinal column, can be determined from clinical findings. Diaphragmatic paralysis occurs with lesions of the upper three cervical segments (transient arrest of breathing from brainstem paralysis is common in severe head injury). Complete paralysis of the arms and legs usually indicates a fracture or dislocation at the fourth to fifth cervical vertebrae. If the legs are paralyzed and the arms can still be abducted and flexed, the lesion is likely to be at the fifth to sixth cervical vertebrae. Paralysis of the legs and only the hands but not the proximal arms indicates a lesion at the sixth to seventh cervical level. Below the cervical region, the spinal cord segments and roots are not directly opposite their similarly numbered vertebrae (Fig. 42-1). The spinal cord ends at the first lumbar vertebra, usually at its rostral border. Vertebral column lesions below this point give rise predominantly to cauda equina syndromes; these carry a better prognosis than injuries to the lower thoracic vertebrae, which involve both cord and multiple roots.