[False negative myelography in surgically confirmed lumbar intervertebral disk prolapse].

A consecutive series of 821 lumbar myelograms in patients operated on for prolapsed disks were analysed. 47 or 5-7% had to be listed false-negative in spite of excellent technical quality. To find out, whether anatomical variations or a special functional state of the subarachnoid space could have prevented a correct diagnosis, clinical symptoms and some special radiological parameters were examined and statistically evaluated: 1. Distances between peduncles of L4, L5, S1 2. Width of subarachnoid space in a coronal section of L4, L5, S1 3. Width of subarachnoid space in a sagittal section of L5 4. Distance between the posterior limit of the body of L5 and the anterior limit of the subarachnoid space. Measurement and statistical correlations did not reveal any correlation between false-negative myelograms and any of the anatomical variants measured. We still cannot rule out false-negative myelograms.