Paraplegia in hyperextension cervical injuries with normal radiographic appearances.

This communication deals solely with a group of cases, hitherto rather obscure, in which damage to the cervical part of the spinal cord occurs without radiographic evidence of vertebral injury or displacement. Two alternative explanations of such injury have been postulated. The first is that the spinal cord pressure is due to acute massive prolapse of an intervertebral disc : but our limited experience of this lesion suggests that as a rule this is recognisable on radiographic examination by narrowing of the intervertebral space. The second explanation is that paraplegia is due to hyperfiexion dislocation which undergoes spontaneous reduction ; but it is doubtful whether this occurs at all, because forward flexion or dislocation of the cervical spine which is sufficient to damage the cord would necessarily be associated with locking of the articular facets, or crush fracture of a vertebra, or both. Neither of these lesions undergoes spontaneous reduction, and moreover both are demonstrable by radiographic examination. \Ve suggest that the usual mechanism of these injuries, in which radiographic examination reveals no significant displacement, is forced hyperextension.