Pantopaque Arachnoiditis

Conflicting opinions exist as to the advisability of removing ethyliodophenylundecylate (Pantopaque; Myodil) from the subarachnoid space after myelography. American authors (1–5) usually favor as complete removal as possible, whereas British workers (6) frequently recommend that the contrast material be left undisturbed. One reason for not removing the medium is the fear of additional trauma to the subarachnoid space. A puzzling aspect of the problem is the fact that reports in the literature show most patients to have very little reaction to Pantopaque (7), while some have had severe late symptoms and at surgery (1, 3–5) or autopsy (3,8) a severe arachnoiditis has been encountered. The idea occurred to us that subarachnoid bleeding during the course of needle positioning might produce an added irritant factor in an occasional patient and thereby explain the development of severe arachnoiditis. Review of the literature available to us has not disclosed any previous investigation of this possibility. Sarkisian (4), in 1956, suggested that “a bloody tap” should be considered a contraindication to the injection of oil intrathecally, evidently basing this recommendation on the possibility of emulsification of oil. Jaeger's (9) studies of the harmful effects of emulsified oils were cited. Because of the difficulty of being certain whether or not subarachnoid bleeding has occurred in human clinical material, it was decided to evaluate the effect of blood mixed with Pantopaque in the subarachnoid space of dogs. The dog is the experimental animal most frequently used for studies of Pantopaque (1, 2, 4, 10). Materials and Methods Four mongrel dogs in good clinical condition were used. In all, the material was injected into the cisterna magna through a posterior mid-line approach with a 20-gauge needle, under strict aseptic technic. Injection was made with the animal in a 60° tilt, the caudal portion lower and the neck flexed. The neck was extended immediately upon completion of the injection. In this position essentially all the material flowed slowly along the subarachnoid space of the cervical spinal cord to the lumbar region over a period of about one hour. After preliminary withdrawal of about 5 ml. of spinal fluid, the injection was made slowly, without trauma, and in a very easy manner in each animal. Radiographs were obtained at the completion of injection and at intervals until the opaque medium reached the lumbar region. The animal was maintained under light pentobarbital anesthesia during this period. The first dog was injected with 3 ml. of Pantopaque alone; the second and third with 3 ml. of Pantopaque plus 3 ml. of blood. The blood was withdrawn from the animal's leg vein immediately prior to injection, mixed with the Pantopaque in the syringe, and injected before clotting occurred. The fourth dog was injected with 3 ml. of unclotted blood.