Evidence for end-to-side sensory nerve regeneration in a human. Case report.

Division of a peripheral nerve produces an axotomy leading to neurite outgrowth from the proximal stump and wallerian degeneration in the distal stump. Because there is no longer a connection between the distal stump and neuronal cell bodies in the anterior spinal cord or dorsal root ganglion, it is assumed that no neurites should exist in the distal stump. The authors present the case of a patient who unexpectedly had a neuroma on the proximal end of the distal segment of a previously severed nerve. The lateral antebrachial cutaneous nerve had been surgically severed. Innervated by the radial nerve, a neuroma subsequently formed in the distal segment. Our hypothesis is that the proximal end of the distal portion of a severed nerve may be innervated by collateral sprouts of axons that branch at points of more distal plexus formation. This invokes a similar pathophysiology to the controversial notion of end-to-side nerve sprouting. Neuromas that develop on the "wrong side" of a nerve become an additional potential source of pain in patients with injured nerves.