An electrophysiological and histological study of myelinated axon regeneration after peripheral nerve injury and repair in the cat.

Electrophysiological and histological methods have been combined to obtain quantitative measures of the success of regeneration of myelinated axons in a cutaneous nerve after injury and repair by a variety of procedures. Following a simple transection injury more axons regenerated successfully when the nerve was repaired by epineurial suturing or stump suturing than when it was left unrepaired; both types of repair gave similar results. After loss of a 10-mm piece of the nerve trunk, repair with an autograft produced more regeneration than when the nerve was left untouched, but repair by stump mobilization with epineurial suturing made matters worse. On the whole, the regenerated afferents had receptive field properties similar to those found in control animals but there was a higher incidence of units that could not be typed using conventional criteria. A small proportion of them had split receptive fields. Fibre diameters and conduction velocities were reduced compared with controls; this was particularly so through the neuroma and in the distal stump. There was also evidence of abnormal interactions, possibly ephaptic, between some regenerated axons.