COMMON FOCAL MONONEUROPATHIES AND THEIR ELECTRODIAGNOSIS

Common focal mononeuropathies can be produced by compression, entrapme nt, crush, stretch, and transection. Injuries resulting from acute or chronic repetitive external pressure produce compressive neuropathy, w hereas chronic distortion or angulation of the nerve from an internal source produces entrapment neuropathy. Electrodiagnostic techniques us ed in the electromyographic laboratory include nerve conduction studie s and the needle electrode examination. Measurement of distal latency, amplitude, conduction velocity, and identification of focal conductio n block may help in the localization of focal mononeuropathies. The ne edle electrode examination gives further information about the distrib ution of nerve damage, the activity and chronicity of axon loss, and c an sometimes date the onset of injury. Basic clinical features and ele ctrodiagnostic patterns are discussed for median, ulnar, radial, and p eroneal neuropathies. Differential diagnosis is provided, and illustra tive cases are presented.