Delayed radiation myelopathy: serial MR-imaging and pathology

Clinical data, MR-scans, time-dose fractionation schemes and neuropathologic findings of two cases of delayed radiation myelopathy (DRM), are presented. Both patients, a 72-year-old diabetic woman with cervical lymphnode metastasis from a squamous cell carcinoma and a 46-year-old woman with tonsillar carcinoma, developed paraparesis followed by quadriplegia, at 7 and at 10 months following radiation. The spinal cord received 46 and 49 Gy. (Fraction dose 2.25 Gy and 2.0 Gy, 4 times/week). Serial MR-scans showed spinal cord enlargement and focally increased signal intensity (T1-gd). The second patient survived and stabilized following therapy with coumarins. The first patient died 13 months after radiotherapy. At autopsy necrosis, local calcium deposits, lipid macrophages and swollen astrocytes were observed in the white matter. There was slight hyalinosis of the intramedullary vessel walls. We conclude that serial MRI may be helpful to distinguish DRM from other causes of spinal cord injury. DRM may occur at a total dose less than 50 Gy. Additional risk factors (diabetes, hypertension), and fraction doses above 2 Gy contribute to the development of DRM.