Total myelography with radiopaque emulsions.

Abstract

Myelography continues to be the basic and essential procedure for the diagnosis of abnormalities of the spinal cord and canal. The shortcomings of the procedure as currently performed are due, in large measure, to the inadequacies of the contrast media. Our experimental studies with various radiopaque emulsions are the subject of this report. Air was the original contrast medium, introduced by Dandy (1) in 1919. Air myelography does not require fluoroscopic manipulation and the air is completely absorbed. However, a large number of inconclusive examinations due to the relatively poor contrast qualities of air and the high percentage of complicating severe headaches have severely limited its use. Positive contrast myelography with iodized oil (Lipiodol) was introduced in 1922 by Sicard and Forestier (2). Although visualization was satisfactory, the medium was too dense, tended to break up into droplets, and was extremely difficult to remove from the spinal canal. Chronic meningeal irritation frequently resulted from the retained oil. Fluoroscopic manipulation was required for moving the oil column. Pantopaque, a less viscous insoluble synthetic oil, was introduced in 1944 (3, 4). It also is practically nonabsorbable and irritating to the meninges if retained, but it is more easily removed because of its lower viscosity. Pantopaque is now the standard myelographic medium in the United States. The shortcomings of conventional myelographic media are obvious and it is readily apparent that the ideal myelographic medium has not been devised. The theoretical criteria of such a medium would be (a) thorough miscibility with the spinal fluid allowing for total opacification of the spinal subarachnoid spaces, (b) satisfactory density which would permit opacification of the spaces and visualization of the cord mass, (c) no toxicity, and (d) complete absorption and elimination of the medium. Theoretically, three types of media are miscible with the spinal fluid and will produce total opacification of the spinal subarachnoid space. These are water-soluble agents, aqueous suspensions of finely divided opaque particles, and emulsions of an opaque oil in water. Water-soluble media: In 1931 Arnell and Lidström (5) introduced water-soluble abrodil (Skiodan) in Sweden. Several other water-soluble preparations have subsequently been tried. Regardless of the chemical structure of the soluble medium, the solution must contain sufficient solute to be adequately radiopaque; this requires a concentration which makes the solution strongly hypertonic and therefore irritating to the meninges. In addition, the chemical nature of the material also contributes to meningeal irritation. The water-soluble preparations, however, are all rapidly absorbed.