Common Focal Mononeuropathies and Their Electrodiagnosis

Common focal mononeuropathies can be produced by compression, entrapment, crush, stretch, and transection. Injuries resulting from acute or chronic repetitive external pressure produce compressive neuropathy, whereas chronic distortion or angulation of the nerve from an internal source produces entrapment neuropathy. Electrodiagnostic techniques used in the electromyographic laboratory include nerve conduction studies and the needle electrode examination. Measurement of distal latency, amplitude, conduction velocity, and identification of focal conduction block may help in the localization of focal mononeuropathies. The needle electrode examination gives further information about the distribution of nerve damage, the activity and chronicity of axon loss, and can sometimes date the onset of injury. Basic clinical features and electrodiagnostic patterns are discussed for median, ulnar, radial, and peroneal neuropathies. Differential diagnosis is provided, and illustrative cases are presented.