Electrophysiological Evaluation Practice Test

Inplexus lesions, because the injury involves a proximal, branching network feeding many nerves, the EMG pattern is not confined to a single nerve territory. Needle EMG tends to show a patchwork of denervation and reinnervation across multiple muscles supplied by different branches of the plexus. You’ll often see active denervation (fibrillation potentials or positive sharp waves) in several muscles, alongside motor units that are large or polyphasic due to collateral reinnervation, leading to a very complex overall picture. This complexity reflects the involvement of multiple nerve roots and trunks and the resulting mix of affected and partially spared fibers, rather than a straightforward, uniform deficit seen with a single nerve lesion. The other descriptions don’t fit: a simple pattern would suggest involvement of only one nerve; no denervation would be unusual with plexus injury; and focusing on decreased conduction velocity in distal nerves points to demyelination in a different setting, not the axonal, multifocal pattern typical of plexus injury.