The oil myelogram after operation for lumbar disc lesions.

Post-operative myelograms in patients with renewed or persistant pain in the back or sciatica after lumbar disc surgery were reviewed in an attempt to differentiate between recurrent disc prolapse and other changes, particularly scarring and inflammation of the meninges. The most useful sign of recurrent disc prolapse was anterior indentation of the iophendylate (Myodil) column opposite a disc space. Inflammatory changes in the meninges were indicated by loculation of the subarachnoid space, matting or marked swelling of the nerve roots, irregularity of the theca, and by the absence of a posterior bulge of the subarachnoid space at the level of the operation. Waisting of the contrast medium column, non-filling of nerve root sheaths, complete myelographic block and posteriorly placed indentations were confirmatory evidence of the presence of disease, but not helpful in determining its nature.