ESTIMULACION REPETITIVA DEL NERVIO (RNS)

Repetitive nerve stimulation (RNS) and single-fiber electromyography (SFEMG) are important confirmatory tests for the diagnosis of disorders of the nicotinic neuromuscular junction, particularly for myasthenia gravis, Lambert-Eaton myasthenic syndrome (LEMS), and botulism. Repetitive nerve stimulation – Repetitive nerve stimulation (RNS) represents a modification of conventional motor nerve conduction studies. The interval between repeated motor nerve stimulations is designed to maximally stress the neuromuscular junction safety factor. (See 'Repetitive nerve stimulation' above.) •Slow RNS – Slow rates of RNS (1 to 5 Hz) deplete the number of quanta of acetylcholine available for release with subsequent depolarizations. In pathologic states where the safety factor for neuromuscular junction transmission is considerably reduced, some muscle fibers will fail to depolarize in the later stimuli of a train and the compound muscle action potential (CMAP) amplitude will drop, which is referred to as a decremental response (waveform 1). A reproducible decrement of >10 percent is considered abnormal in most muscles. •Rapid RNS – In disorders of the presynaptic terminal of the neuromuscular junction, where the number of released vesicles is markedly reduced, voluntary maximal isometric muscle contraction or high-frequency RNS can markedly increase the release of acetylcholine and thus enlarge the size of the resultant CMAP amplitude and area, which is referred to as an incremental response (waveform 2). <a id="