Myelography in Spinal Metastases

During the past five years a total of 75 tumors involving the spinal canal have been studied by myelography at Montefiore Hospital. Twenty (27 per cent) of these proved to be metastatic cancer and 6 (8 per cent) lymphoma, a total of 26 (35 per cent). The relatively high incidence of malignant tumors in this series can be explained by the fact that the institution from which this report emanates has a large, active neoplastic service, and patients are maintained under surveillance for the duration of their illness. The experience of others indicates a much lower frequency of spinal metastatic tumors. Sachs (15) found 20 (9 per cent) metastatic carcinomas and 28 (12 per cent) sarcomas (no further specification as to type) in a total of 234 spinal tumors. Elsberg (9) encountered only 14 (5 per cent) metastatic tumors in 267 cases. Wood (20) indicates the incidence to be 10 per cent. However, he makes no mention of lymphoma. Lymphomas of the spinal canal are less frequently encountered than would be implied by our statistics. Small collections of cases of lymphosarcoma (total of 20) have been reported in the past by Davison and Michaels (7), Browder and deVeer (4), Drake (8), Verda (18) and Shenkin, Horn and Grant (16). In a recent article on cord compression by Hodgkin's disease, by Smith and Stenstrom (17), the total number of cases of this disease with involvement of the central nervous system described in the literature was brought to about 66. Pathology Several mechanisms have been described to explain the occurrence of metastatic lesions in the epidural space of the spinal canal. 1. Hematogenous Spread: Tumor may seed in the spine via the arterial system. A primary pulmonary tumor may embolize directly into a pulmonary vein, avoiding the capillary bed. This holds true, also, for tumors which have metastasized to the lung and thus set up foci for further dissemination. Controversy exists regarding the ability of metastatic cells passing through the right side of the heart to filter through the lung. 2. Vertebral Vein System: The role of the vertebral veins in metastatic processes involving the spine was described initially by Batson (1, 2). This auxiliary system consists of a collection of valveless veins producing a rich anastomosis about the pelvic region, the vertebral column, and the cranium. The blood is carried through this system under low pressure, and the flow may be subject to arrest and even reversal in direction away from the heart. Batson showed experimentally in human cadavers and monkeys that, with increased intra-abdominal pressure, the venous blood flow from the pelvis and abdomen would not be through the portocaval channels but rather through the vertebral system of veins.