The possible role of regenerating axons in pain persistence after brachial plexus grafting

We tested the hypothesis that chronic pain in patients with grafted brachial plexus injuries stems from regenerating axons. Eight patients who had undergone brachial plexus grafting still reported persistent pain 24 months after surgery, and were followed for an additional 6 months. After recording each patient's self-reported pain severity using a 10-point verbal analogue scale, a tourniquet was inflated in the injured arm for 90 seconds. Then, patients were asked again to rate their pain. Finally, anesthetic blocks were administered to the nonavulsed C5 root. After tourniquet application to the injured limb, pain significantly decreased by 85% (P < 0.001) in all grafted patients. Anesthetic blocks yielded at least 90% pain reduction. Our findings suggest that pain after brachial plexus injury arises from nonavulsed rather than avulsed roots. After grafting, regenerating axons which have attained the periphery might be responsible for pain maintenance.