Use the distribution of amplitude loss and the motor unit pattern together rather than in isolation, because either one alone can mislead localization. Conduction block points to demyelination or focal entrapment, while long-duration polyphasic units favor chronic reinnervation.

A 50 percent CMAP drop across a segment is classic evidence of conduction block; Myopathy tends to show small, short-duration motor units; Neuropathy tends to show large, long-duration, polyphasic motor units; Needle choice affects what you can measure and how easily you can sample a muscle; Recruitment and spontaneous activity should be analyzed with the morphology