Delayed radiation myelopathy in man: Report of twelve necropsy cases

Abstract

The necropsy findings in 12 adult humans with myelopathy following conventional X-ray, 60Co or betatron radiotherapy of cervical and mediastinal tumours are reported. The latencies varied from 3–41 months, survival time after the onset of neurological defects ranged from 3 weeks to 75 months. No relations of latency and clinical course to calculated maximum-minimum cord doses could be established. Time-dose considerations showed that the average cord doses in all except 2 cases were above the tolerance levels suggested by Franke (1963). “Early” delayed lesions occurring in 2 patients 26 weeks and 12 months, resp., after irradiation took the form of spongy demyelination and astroglial reaction with loss of oligodendroglia in the absence of definite vascular lesions. Later stages of delayed radiation myelopathy were largely consistent with those of earlier reports. Telangiectasias and relative preservation of nerve cells were constant findings. One case showed flaky demyelination of thoracic nerve roots associated with almost complete transverse necrosis of the dorsal spinal cord. The pathogenesis of delayed radiation lesions of the spinal cord is discussed in relation to recent experimental data. Biophysically induced lesions of the oligodendroglia and damage to the vascular endothelium together with secondary permeability disorders of the blood-brain barrier are suggested as the most important factors. The causes of individual susceptibility to radiation are still unknown. No relation between hypertension and regional selectivity or development of delayed radiation damage to the spinal cord was noted in the present and comparable human case series. The concepts of threshold levels of the human spinal cord in relation to radiation damage are not yet clearly defined.