Single fiber EMG (SFEMG) is an electrophysiological technique that can provide useful informations about the physiolohy and pathophysiology of the Motor Unit and mainly of the neuromuscular junction. A special needle is needed for measuring fiber density, the number of single muscle fiber potentials recordable in the pick-up area of the electrode. Fiber density is altered whenever a rearrangement of Motor Units takes place. For recording neuromuscular jitter however a conventional needle can be used. Abnormally increased neuromuscular jitter and neuromuscular blocks can be detected in patients affected by diseases of the neuromuscular junction. SFEMG is the most sensitive electrophysiological test for myasthenia gravis and other neuromuscular junction pathology.
The lesson will provide definition of SFEMG and single fiber potential, technical information on SFEMG needle and recording techniques including machine setting and software needed to perform and analyze the SFEMG examination. Mean parameters of SFEMG, fiber density and jitter, will be specified. Moreover the stimulated SFEMG and the volitional effort SFEMG will be discussed. Jitter analysis, normative data and criteria for abnormality will be described. Examples of recordings in normal and pathological conditions will be showed. Usefulness and limits of the technique will be outlined.
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