Evaluation of the role of magnetic resonance myelography in lumbar spine imaging

The purpose of our study was to evaluate the accuracy of MR myelography in depicting disc herniation in the lumbar spine when compared with convention al MRI in patients presenting with clinical evidence of disc herniation. On e hundred patients re for conventional MR imaging of the lumbar spine also had coronal MR (TR 9000 ms, TE 272 ms eff, NEX 3, echo train length 32) mye lography performed. Three experienced observers compared magnetic resonance myelography (MRM) with conventional lumbar spine MR using the following va riables: visibility of thecal sac and nerve roots, and the presence, locati on and severity of disc herniation. Disc protrusions were seen at 110 disc space levels on conventional MR images as apposed to 93 on MRM. However, on ly 72% of lesions seen on conventional MR were diagnosed by MRM. Similarly only 63.8% of nerve root compression abnormalities seen at:conventional MR were visualized when compared with conventional MRM. The sensitivity, speci ficity and accuracy of MRM when compared with conventional MR was 72, 93 an d 85%. respectively. The MRM technique yields images that resemble conventi onal myelography and may be used to help confirm abnormalities seen on conv entional MR in selected cases; however,the large number of false-positive a nd false-negative examinations indicates-that caution should be used in int erpreting MRM images.