Role of stenosis of spinal canal in L4-L5 nerve root compression assessed by flexion-extension myelography.

Myelographic flexion-extension studies were performed in four groups of 10 patients each, with (A) normal myelogram; (B) bilateral nerve root compression at L4-L5; (C) unilateral nerve root compression at L4-L5 and (D) nerve root compression at L5-S1. The aim of the investigation was to assess the role of spinal stenosis in contributing to nerve root compression. The results indicate that a form of stenosis of the spinal canal plays an important role in bilateral nerve root compression at L4-L5, and to a lesser extent in unilateral nerve root compression at L4-L5. It does not appear to play a role in L5-S1 nerve root compression (stenosis of the lateral recess left aside). It is advocated that in myelographic L4-L5 nerve root compression additional flexion-extension studies should be performed in order to evaluate the possible role of stenosis of the spinal canal contributing to this compression. Even in nerve root compression by disc extrusion, concomitant spinal stenosis may necessitate additional decompressive laminectomy.