Clinical Evidence of Retrograde Axonal Growth in Chronic Brachial Plexus Injury.

Nerve axons grow from proximal to distal after axonometric injury; however, they have been seen to regenerate via alternate routes, with some also demonstrating retrograde growth in neuromas. We present the case of a 33-year-old male with a 16-year-old traumatic brachial plexus injury presenting with neuropathic pain and isolated spontaneous recovery. Following a successful pre-operative anaesthetic block, a neurectomy of the median and ulnar nerves was planned for pain relief. Intraoperatively, median nerve stimulation resulted in muscle contractions in the pectoralis major (PM) and extensor carpi radialis brevis (ECRB). This was confirmed by electrical and mechanical stimuli. Histological analysis confirmed the presence of viable axons in the median nerve despite no distal nerve function. Post-surgery motor activity was preserved. A plausible explanation for the intraoperative observations, suggesting neural connectivity between the median nerve and PM and ECRB, would be retrograde growth into various nerve pathways. Alternative explanations such as axonal bifurcation, light anaesthesia, or anatomical variations were considered but the evidence favoured retrograde axonal regrowth. These findings challenge conventional understanding and offer potential new approaches to nerve reconstruction.