Effects of continuous epidural block on motor nerve conduction velocity in patients with lower spine disorders.

Thirty-one patients with severe low back pain were treated by continuous epidural block for 18±3 (mean±SEM) days. Motor nerve conduction velocity (MCV) of the common peroneal nerve was measured before and after the treatment. After the treatment, the visual analogue scale score (VAS) and straight leg-raising (SLR) test were markedly reduced (P<0.01), and MCV was increased significantly (P<0.001). A significant correlation (P<0.01) between the SLR test and MCV was found before the treatment. A significant correlation (P<0.001) between VAS and MCV was demonstrated after treatment. However, in three patients who showed no reduction in VAS even after the treatment, MCV became significantly (P<0.05) slower in spite of nearly normal SLR test results. These results suggest that epidural block treatment improves not only pain but also MCV, and that two parameters, SLR test and pain intensity, are related closely to the MCV.