A comparison of myelography and computer tomography in lumbar disc herniation.

We report a retrospective study of 219 patients with lumbar disc lesions in whom the operative findings were compared with the results of computer tomography (CT) and myelography. When used alone each method achieved virtually the same degree of accuracy (87.8% and 87.4%). Particular attention was paid to 70 "problem" cases in whom the initial CT diagnosis suggested herniations at different levels which were not in keeping with the clinical symptoms or signs. The operative findings showed that CT had produced 10.4% false positives and 4.4% false negatives. The corresponding results for myelography were 5.9% and 8.9%. Myelography is, therefore, a more exact method of diagnosis for segmental and lateral herniations. After initial computerised tomography, myelography is indicated when there is a discrepancy between CT and the clinical findings.