[Damage to the spinal medulla caused by radiation].

The current clinical and biological knowledge about radiation myelopathy is reviewed. Transient myelopathy with Lhermitte's sign develops within months after irradiation. Symptoms generally disappear within months without treatment. Chronic progressive radiation myelopathy develops with a latency of several months to years after spinal cord irradiation. The symptoms are paraesthesia, paresis or paralysis, leading to severe physical disability and eventually death due to secondary infections. The long term survival after myelopathy is 30% for cervical myelopathy and 70% for thoracic myelopathy. There is no effective treatment. Analysis of clinical reports shows that the risk of developing chronic myelopathy is less than 2% after 55 Gy, given in 2 Gy daily fractions. Other important radiobiological risk factors (dose per fraction, interfraction interval and volume) are discussed.