Contribution of collateral sprouting to the sensory and sudomotor recovery in the human palm after peripheral nerve injury

The contribution of collateral sprouting to the sensory and sudomotor recovery was studied in 52 patients aged 3-66 years (mean 35.5 years) from 2 to 9 years following nerve injury and repair. The study included three groups of patients: (1) patients with complete division of median and ulnar nerves (skin reinnervation exclusively due to axon regeneration), (2) patients with isolated division of ulnar or median nerve (skin reinnervation due to axon regeneration and possible collateral sprouting), and (3) patients in whom injured axons failed to regenerate (skin reinnervation exclusively due to collateral sprouting). The end stage of sensory and sudomotor recovery was studied by: clinical methods, sensory nerve action potential (SNAP) measurements, sympathetic skin response (SSR) and the ninhydrin test. We found that recovery of sensory and sudomotor function in groups 1 and 2 was similar. End-stage sudomotor and sensory recovery within the autonomous area of the nerve did not depend on possible collateral reinnervation. Collateral reinnervation from the uninjured nerve was limited to the border innervation area of the palm and ring finger. Adjacent uninjured nerve may contribute to sprouting of nociceptive axons providing a protective function.