Radiation myelitis of the dorsolumbar spinal cord.

Abstract

RADIATIONMYELITIS is a rather rare complication following therapeutic irradiation to neoplasms in which the spinal cord has been unavoidably included in the treatment portals. Since 1940 a total of 15 cases of myelitis involving the thoracolumbar spine has developed in association with the treatment of testicular tumors at Walter Reed General Hospital, Washington, D. C. The present paper is an analysis of these cases and will report on the relative risk of developing injury to the thoracolumbar spinal cord following such irradiation. Methods In the last twenty-eight years over 800 malignant germ-cell tumors of the testicle have been treated at Walter Reed General Hospital. Irradiation has been one of the primary modalities in treatment, principally to the lymphatic pathways draining the testicle following orchiectomy. This irradiation has been given prophylactically or therapeutically, either in conjunctionwith or without a retroperitoneallymphadenectomy. In most patients the fields included the inguinal and iliac lymph nodes on the involved side as well as the para-aortic lymph nodes to the level of the diaphragm. In a number of cases the lymphatic pathways of the mediastinum and left supraclavicular areas were also included. A total of 343 patients who received irradiation to these lymphatic pathways and survived a minimum period of three years is available for study. Of this group there were 313 in whom coplanar anterior and posterior opposing portals included the spinal cord in the field of irradiation. In these the spinal cord dose could be accurately calculated. The remaining 30 patients had angled fieldsor rotational therapy, and insufficient information is available for adequate dose calculations to the spinal cord. The source of radiation for this group of 313 patients is shown in TABLE I. Certain assumptions were made in dosage caIculations to the spinal cord. The overall bone density was taken as 1.40 g/cc. The average bone thickness posterior to the spinal cord was taken as 1.0 cm; the average thickness anterior to the spinal cord was taken as 3.0 ern. All dosage calculations were to the anterior aspect of the spinal canal which approximated 6.5 em depth in the lumbar area, 4.8 ern in the lower thoracic area, and 5.0 em for the high thoracic fields from the posterior skin surface. Clinical Features Symptoms of radiation myelitis with the therapeutic doses of radiation commonly employed are usually delayed and most often appear about one year following irradiation. In the present series the earliest symptom was seen at four months and the longest at thirteen years. Reagan et at. (20) have recently reviewed the clinical findings in radiation myelopathy and grouped the clinical manifestations into 4 major syndromes.