[Investigation of pseudolocalizing signs in the lumbar region: analysis of L5 monoradiculopathy due to upper lumbar compressive lesions].

Background And Purpose: Pseudolocalizing signs in lumbar spinal disease seems to be rarely encountered. To our knowledge, only six cases which caused L5 monoradiculopathy due to upper lumbar lesions have been described. We retrospectively reviewed patients with similar signs in our center, and we discussed the pathogenesis of such interesting neurological signs depending on our own and reported cases.

Results: Between January, 2005 and August, 2010, 1,229 patients with lumbar degenerative disease underwent spinal decompression surgery, 3 of which (0.24%) presented with L5 monoradiculopathy due to upper compressive lesions in lumbar spinal disease.

Discussion And Conclusion: As pathological mechanisms, 2 hypotheses are speculated: Direct compression at the epiconus level or circulatory disturbance at the nerve root itself. If the level of the conus medullaris is situated at the lower lumbar level, such as L2 level, a compressive lesion at the L1-2 level, for example lumbar disc herniation, can compress the L5 nerve root resulting in L5 nerve palsy. However, the affected level below the cauda equina doesn't seem to compress only the L5 nerve root directly, because the cauda equina is mobile enough to avoid the compression. Another speculated mechanism is the so-called circulatory disturbance. When the cauda equina is remarkably compressed at the upper level, less severe compressive change may cause selective monoradiculopathy at the lower lumbar level. Based upon the presented analyses, we adopt the circulatory mechanism in our cases as the causative factor in lumbar pseudolocalizing signs.