Air Myelography in the Diagnosis of Intraspinal Lesions Producing Low Back and Sciatic Pain

Abstract

VISUALIZATION of the spinal canal by the use of air as a contrast medium was suggested by Dandy (1), in 1918, but until recent years the necessary combination of good detail and adequate contrast in roentgenograms was not available. In 1934, Coggeshall and von Storch (2) showed that the lumbo-caudal sac could be visualized by air but their report was limited to the findings in three normal patients. The same year Van Wageneen (3) reported three cases of complete spinal block in which the lower level of the lesion was visualized by injection of small amounts of air. Our use of air was prompted by our desire to find a substitute for lipiodol because of the possible harmful effects of lipiodol on nervous tissue and the necessity of laminectomy for its removal. Gaseous contrast media, such as air or oxygen, are readily absorbed and, therefore, spinal canal visualization need not be restricted to patients whose symptoms and neurologic findings are clearcut.2 This means that a contrast medium will be used more often and a greater number of patients with low back pain will have the benefit of this procedure if air is used instead of lipiodol. We have used air myelography routinely for the past three years in all patients who have had symptoms and sufficient neurologic findings to make us suspect an intraspinal lesion. The method is applicable for a lesion at any level in the spine but is especially valuable to demonstrate the lumbo-caudal sac. The lumbo-caudal sac should be examined in any patient with persistent sciatic pain who exhibits abnormalities in the Achilles reflex, in sensation especially to heat or cold over the dorsum of the foot, or impairment of muscle power in the foot. Our experience is based on the findings in over 150 cases of myelography, and in more than half of this number the lumbo-caudal sac was studied. Ten of the group of patients who had positive findings in this region after air injection came to operation and in each case the uncovered lesion was at the exact level demonstrated by the roentgenograms. The method is not misleading as we have not had any cases in which the myelograms indicated a lesion without finding it at operation. Of the ten cases operated on, herniated disc was uncovered in four, neoplasm in three, hypertrophied ligamentum flavum in two, and arachnoiditis with hour-glass constriction in one. The diagnosis of an intraspinal tumor or space-taking lesion depends upon the indentation of, or the encroachment upon, the limiting membrane of the lumbo-caudal sac. The boundaries of the subarachnoid space are sharply delineated by air so that any change of configuration of the margins can be visualized by roentgenograms. A herniated cartilaginous disc carries the posterior longitudinal ligament dorsad so that an indentation of the ventral aspect of the air column is produced (Fig. 2).