On ''Pre- , Intra- , and Postoperative Electrophysiologic Analysis of the Recovery of Old Injuries of the Peripheral Nerve and Brachial Plexus after Microsurgical Management'' (Journal of Reconstructive Microsurgery 2002;18:77-82)

Alon and Rochkind (Pre-Intra-, and Postoperative Electrophysiologic Analysis of the Recovery of Old Injuries of the Peripheral Nerve Brachial Plexus after Microsurgical Management. J Reconstr Microsurg 2002;18:77-82) have defined supported, by using a strong statistical model something senior surgeons have noted anecdotally for years-that muscle motor endplates in large volume muscles can survive for long periods of time and be reinnervated. The authors furthermore document that the nerves respond to changes in their environments following surgery years after injury.

The authors propose a correlation between clinical function the outcome of motor unit recruitment during electromyography. This significant idea supported by personal observations needs to be considered. However to do this we need some defined parameters of voluntary recruitment. The number of M waves per unit of time the mean motor unit potential during recruitment are essential parameters. The authors have provided guidelines needed while recording but have not defined the endpoints of those measurements.

Kline for decades has heralded the benefits of neurolysis these authors also advocate external internal neurolysis. In my experience internal neurolysis is possible only proximal distal to the dominant site of injury unless the injury did not disrupt the nerve produced Sunderland types 1, 2, or 3 injuries. Traction or severance as in Sunderland types 4 or 5 injuries produce a neuroma with its characteristic mini-fascicles. In my experience neurolysis through this type of neuroma is difficult in the best of circumstances may harm the nerve in the worst of circumstances. The authors do not state how many injuries appeared to have started primarily as Sunderland types 4 or 5 injuries.

This study is significant but has some apparent flaws. Six of 28 cases were upper extremity injuries while 22/28 were lower extremity injuries the authors do not define the parameters of recording in the lower extremity. While recruitment patterns are correlated with function the authors have not told us what muscle groups they recorded from or if they selected specific muscles for specific nerves. The function of the tibialis anterior peroneus >longus after a common peroneal injury would have greater meaning than recruitment of muscle activity in the extensor digitorum communis of the lower extremity. We are asked to compare recruitment to function but >is this comparison by muscle group or by individual muscles?

I have always been suspicious of improved amplitude of M waves as an assessment during surgery because of myorelaxant agents. Assessment early in the surgical procedure vs. later in the procedure could be influenced by a slow decay of the effect of the muscle-relaxing agents. However while the M wave would be influenced the latency of the nerve would not be affected by myorelaxant agents. The authors noting that the latency changed following neurolysis indicate something is happening immediately after neurolysis. Because of the rapid change in latency one can speculate that it is probably related to the blockage of rapid axoplasmic flow through the site of the nerve injury. That by releasing the fibrous tissue associated with the nerve the axoplasmic flow benefits. Whether antegrade retrograde, or both exoplasmic flow or other factors contribute to the change in latencies is not clarified.

In their series the authors report six cases of sciatic nerve clinical experience. There is little information given on neurolysis of nerves in the lower extremity particularly regarding the sciatic nerve. I hope that in the future the authors will provide a separate report on their experience with injuries neurolysis of the sciatic femoral nerves.