Traumatic Peripheral Nerve Lesions Follow-up
- Author: Neil R Holland, MBBS, MBA, FAAN; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE more...
Further Inpatient Care
An attempt should be made to classify all nerve injuries according to the completeness of the injury and the predominant pathophysiologic process involved: however, recognize that individual fascicles can be affected differently.
The results of nerve conduction studies may be difficult to interpret during the first 10 days after nerve injury until the effects of wallerian degeneration have had a chance to fully evolve in both motor and sensory fibers.
The best measure of axonal loss is the amplitude of the evoked CMAP response (compared to the other side) in a weak muscle from nerve stimulation distal to the injury site at least 7 days after the injury.
The density of denervation potentials in weak muscles is a poor measure of axonal loss. Denervation potentials may be absent for as long as 14-21 days after nerve injuries with severe axonal loss. Denervation potentials may be "profuse" in mixed injuries, even if the predominant pathophysiologic process is neurapraxia.
The presence of voluntary motor unit potentials in a clinically paralyzed muscle indicates that the nerve injury is partial, even if the distal CMAP response is absent.
Intraoperative nerve conduction testing often is required to differentiate axonotmesis from neurotmesis in closed nerve injuries that appear continuous. However, beware of "super normal" NAPs with more proximal nerve root avulsions.
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