Pain following human brachial plexus injury with spinal cord root avulsion and the effect of surgery

Brachial plexus injury leading to spinal cord root avulsion in humans produces a characteristic constant crushing and intermittent shooting pain, which is often intractable. Preliminary observations suggested that this pain might be alleviated after successful nerve transfers to restore limb function. We therefore studied a group of 14 patients prospectively, to establish the validity of this observation, and to elucidate the underlying mechanisms. We found a strong correlation and temporal relationship between reduction in pain and successful nerve repair. All five patients with motor recovery experienced significant relief of de-afferentation pain, while in the seven patients with persistent pain, none had motor recovery. There was no correlation between pain relief and the minimal recovery of sensation in some cases, and no case had any return of sensory or sympathetic cutaneous axon-reflexes. While skin sympathetic axon-reflexes were reduced with T1 root lesions, there was no relationship between T1 root damage and pain. It was concluded that nerve repair can reduce pain from spinal root avulsions and that the mechanism may involve successful regeneration, and/or restoration of peripheral connections prior to their function, possibly in muscle.