Pain phenomena and sensory recovery following brachial plexus avulsion injury and surgical repairs.

Seventy-six patients with severe brachial plexus avulsion injuries were studied using pain questionnaires and quantitative sensory testing. There was significant correlation between pain intensity and the number of roots avulsed prior to surgery (P=0.0004) and surgical repairs were associated with pain relief. Sensory recovery to thermal stimuli was observed, mainly in the C5 dermatome. Allodynia to mechanical and thermal stimuli was observed in the border zone of affected and unaffected dermatomes in 18% of patients assessed early (<6 months) and 37% patients at later stages. Pain and sensations referred to the original source of afferents occurred at a later stage (>6 months) in 12% of patients and were related to nerve regeneration. By contrast, "wrong-way" referred sensations (e.g. down the affected arm while shaving or drinking cold fluids) were reported by 44% of patients and often occurred early, suggesting CNS plasticity. Understanding sensory mechanisms will help develop new treatments for severe brachial plexus injuries.