Lumbar disk herniation: diagnosis with CT or myelography.

The value of computed tomography (CT) and myelography as single investigations in the diagnostic evaluation of patients with radiating leg pain probably due to lumbar disk herniation (LDH) has been adequately demonstrated. However, the extent to which CT can replace myelography and the conditions in which the examinations should be combined and in which order are still uncertain. Results of CT scans and myelograms from 461 patients with symptoms of lumbar root compression, probably due to LDH, were evaluated and compared with surgical results, if available. The sensitivity of myelography exceeded that of CT (82% vs. 73%), but its specificity was lower (67% vs. 77%). The positive predictive value of myelography only slightly differed from that of CT (93% vs. 94%). These results were used to establish a sequential diagnostic workup for patients with radiating leg pain. If, in this population with a high prior probability for surgery, CT had been the investigation of first choice in patients suspected of having LDH, the number of myelographic procedures performed could have been reduced by two-thirds.