Pain after avulsion injuries and complete palsy of the brachial plexus: the possible role of nonavulsed roots in pain generation.

OBJECTIVE: Pain after complete brachial palsy has been attributed to the deafferentation of the spinal cord subjected to root avulsion. However, the large majority of patients have at least one nonavulsed root. We postulated that pain, be it subacute or chronic, originates in the stump of the nonavulsed roots.
METHODS: Thirty-six patients underwent brachial plexus grafting within 8 months of their initial injury. Ten other patients with palsy that had lasted for more than 2 years underwent selective, computed tomography-guided anesthetic blocks of the nonavulsed root. Pain was evaluated at different intervals, using a numerical scale ranging from 0 (no pain) to 10 (severe pain).
RESULTS: In all groups, pain decreased substantially or disappeared after a local anesthetic block or grafting. In the patients who underwent grafting, pain reduction was noted the first day after surgery in 56% of the 36 patients. Three weeks after surgery, pain decreased dramatically, by 80% (P < 0.001). By 12 months after surgery, pain had decreased by 90%, and within 24 months, by 95%. Only the difference between 3 weeks and 24 months after surgery was significant (P < 0.001). At final evaluation, 80% of the patients receiving grafts reported either no or minimal pain.
CONCLUSION: Our data suggest that nonavulsed roots mediate pain in subacute and chronic complete brachial plexus palsy.