Involvement of a sensory afferent pathway in human discogenic low back pain - Comparison of upper and lower spinal nerveblock effects on discogenic low back pain

To clarify the afferent pathways from intervertebral discs to dorsal root ganglia (DRGs) in humans we evaluated the effect of an upper and lower spinal nerve block on discogenic low back pain. Patients suffering from discogenic low back pain originating from the L4/5 or L5/S1 intervertebral disc received a spinal nerve root block (L2 nerve block group: n=34, L4 or L5 nerve block group: n=34). Lidocaine (1.5 ml of 1% solution) was administrated to L2, L4, or L5 spinal nerves. In both groups, spinal nerve blocks were significantly effective in alleviating discogenic low back pain (P<0.05). Fifteen minutes after the block, the average visual analogue pain scale score decreased from 8.0 to 4.3 (L2 root block group) and from 7.8 to 3.4 (L4 or L5 root block group). The average effective period was significantly longer in the L2 root block group (13 days) than in the L4 or L5 root block group (8 days) (P<0.05). The upper and lower spinal nerves appear to include sensory afferent nerves from the L4/5 or L5/S1 intervertebral disc. There were differences in the intensity and the period of effective relief between the upper and lower nerve block.