[Electrophysiological exploration of tunnel syndromes].

The compressive neuropathies often lead to segmental demyelination injury. These injuries can be detected using speed motor conduction and sensitivity conduction. The corresponding abnormalities are localized conduction abnormalities, presenting as deceleration or as a conductive block. Segmentary deceleration is perfectly well observed, such as in cases of carpal tunnel syndrome. The detection examination, recording motor unit potentials, can distinguish between a peripheral injury and a central injury as well as between a neurogenic injury and a myogenous injury. The precise study of the sensitivity potentials makes it possible to distinguish between a radicular injury, in which the sensitivity potentials are normal, and a plexus injury, in which the sensitivity potentials are altered because of a postganglionic injury.