Chapter 13 Neurography – motor and sensory nerve conduction studies

Publisher Summary Sensory- and motor-nerve-conduction studies are among the most important single methods used in a clinical neurophysiology (CNP) laboratory. Neurography is essential in the diagnosis of both local and diffuse neuropathies, and it can be used to localize and characterize the severity and pathophysiology of neuropathies. A nerve is usually stimulated at points where it is easy to reach and allow transcutaneous stimulation; these points are called “stimulation sites.” The part of the nerve between two stimulation sites is called a “nerve segment.” In a fractionated study, two or more adjacent nerve segments are studied in the same nerve. Motor-nerve-conduction studies yield several parameters that can be measured. In all electromyography (EMG) laboratories, the maximal motor nerve conduction velocity (CV) and the distal latency (DLAT) are measured. The CV represents the function of only the fastest fibers. The amplitude and shape of the M-wave can also be measured. In addition, the proportional change in the amplitude and duration of M-waves can be assessed when a conduction block is suspected.