A comparison of myelopathy associated with megavoltage irradiation and remote cancer.

Two middle-aged women with malignancy of the aerodigestive tract were treated by megavoltage irradiation. Both subsequently developed transverse myelopathy. The diagnosis of radiation myelitis was rendered in one. The other was thought to have metastatic compression of the spinal cord; in this case, evidence was such that radiation myelopathy also was appropriate. The irradiation dose-time relationships in both patients were biologically low compared to published isoeffect curves available in the literature. The first patient had injury within the irradiated region and the main neurological damage was found there. In the second patient the entire spinal cord was necrotic, clearly placing the second case outside the radiation myelopathy syndrome. Gross and microscopic examinations of the tissues of these two patients show that the remote effects of malignancy upon the central nervous system can imitate the clinical picture of radiation myelitis.