Permanent radiation myelopathy

Because of the morbidity and mortality associated with radiation myelopathy, radiation injury to the spinal cord has been the subject of more clinical reports than any other normal-tissue injury. The spinal cord is perhaps second only to skin as the organ most frequently studied by radiobiologists. Its response has been investigated in mice, rats, cats, guinea pigs, rabbits, pigs, dogs, and rhesus monkeys—virtually every laboratory animal species. Given this level of attention, it is surprising what is not known about the radiation response of the spinal cord. Relatively few animal studies have been performed on the effect of cytotoxic drugs on the radiation response of the spinal cord, the age effects, the effects of blood pressure or other physiological conditions that are controllable in the laboratory, or the relative response of various anatomical levels of the spinal cord. In addition to these unresolved factors, the dose response in the human is still poorly defined. However, as a result of the attention this injury has received, substantial information is available on the diagnosis, pathogenesis and dose fractionation dependence. This review seeks to establish the facts, expose the myths and define the issues still in dispute regarding radiation-induced myelopathy.