Assessing motor nerve lesion from CMAP decomposition

Quantitative characterization of peripheral nerve lesion has been facilitated by estimating the distribution of added delays (DADs) from the compound nerve action potentials (CAPs) evoked from stimulating the proximal and distal site of the lesion. In this paper, compound muscle action potentials (CMAPs) are proposed for estimating the DADs of motor nerves. A case of ulnar nerve entrapment at elbow is used to illustrate the assessment methods where the CMAPs above abductor digiti minimi (ADM) are recorded from stimulating ulnar nerve at wrist, at below-elbow, and at above-elbow. Three kinds of approximation are proposed to assess the motor DAD based on the MUAP-CMAP model. A simplified method could provide a more sensitive noninvasive assessment on motor nerve lesion.