Recovery of cutaneous pain sensitivity after end-to-side nerve repair in the rat

Object. The hypothesis that collaterally sprouting axons from an uninjured donor nerve may provide recovery of pain sensitivity in the skin after end- to-side nerve repair was investigated in rats. In addition, the effect of t his technique on the donor nerve was examined. Methods. The distal stump of the transected peroneal nerve was sutured end to side to the intact sural nerve. No epineurial window or perineurial slit was made in the,ural nerve at the site of coaptation. Other nerves in the leg were transected and ligated. Eighteen weeks later, the sural nerve was transected at a site distal from the coaptation site. The residual pain sen sitivity in the peroneal innervation field in the instep was documented usi ng the skin pinch test in three of 11 animals. The area of sensitivity enco mpassed 19 to 40% of the maximum nociceptive innervation area of the normal peroneal nerve. The nerve pinch test revealed functional sensory axons in all communicating peroneal nerves, in which 277 +/- 119 myelinated axons (m ean +/- standard deviation) were found by histological investigation. Conclusions. The authors conclude that at least partial recovery of sensory function due to collateral sprouting of axons after end-to-side nerve repa ir is possible in principle. However. the presence of functional sensory ax ons in the peroneal nerve stumps did not guarantee the recovery of skin sen sitivity to pain in all animals. No functional or morphological evidence of an untoward effect of collateral sprouting into the end-to-side communicat ing nerve was detected in the axons of the donor nerve itself.