TwitchMeSweetheart
Well-known member
I may have got this link here but I found it to do a pretty good job of summing EMG's up. Parts are a bit technical, but I find the fasciculation section to support a lot of what has been said here many times. Fasciculations by themselves are pretty meaningless.
Fasciculation potentials are another type of spontaneous activity. In contrast to fibrillation potentials, which are produced by single denervated muscle fibers, fasciculation potentials are generated by motor units or portions of motor units. Thus, they are considerably larger than the typical fibrillation potential. Moreover, because the motor unit generating them must be intact to do so, they are evidence of motor unit irritation, rather than motor unit disintegration, as are fibrillation potentials. Finally, from the viewpoint of recognition, fasciculation potentials typically fire irregularly, whereas fibrillation potentials characteristically fire with metronomic regularity. Although fasciculation potentials theoretically can be seen with any PNS disorder, in fact, they are relatively uncommon and most often limited to those that are causing focal demyelination and are chronic in nature (e.g., ulnar neuropathy at the elbow, radiation plexopathy, multifocal motor neuropathy). In regard to intraspinal canal disorders, fasciculation potentials may occur with almost any one of them, including intramedullary neoplasms and radiculopathies, although they rarely have any diagnostic significance in these instances. The sole exception is one of the AHC disorders, ALS, in which their presence is nearly mandatory for diagnosis. The most common situation in which fasciculation potentials appear, however, is the benign fasciculation syndrome. As its name implies, this disorder (if it can be designated as such) consists solely of an otherwise healthy person's experiencing widespread, persistent fasciculations, and often cramps as well. (Because both fasciculations and cramps are caused by muscle membrane irritability, they often are seen together) (5,9,13).
Fasciculation potentials are another type of spontaneous activity. In contrast to fibrillation potentials, which are produced by single denervated muscle fibers, fasciculation potentials are generated by motor units or portions of motor units. Thus, they are considerably larger than the typical fibrillation potential. Moreover, because the motor unit generating them must be intact to do so, they are evidence of motor unit irritation, rather than motor unit disintegration, as are fibrillation potentials. Finally, from the viewpoint of recognition, fasciculation potentials typically fire irregularly, whereas fibrillation potentials characteristically fire with metronomic regularity. Although fasciculation potentials theoretically can be seen with any PNS disorder, in fact, they are relatively uncommon and most often limited to those that are causing focal demyelination and are chronic in nature (e.g., ulnar neuropathy at the elbow, radiation plexopathy, multifocal motor neuropathy). In regard to intraspinal canal disorders, fasciculation potentials may occur with almost any one of them, including intramedullary neoplasms and radiculopathies, although they rarely have any diagnostic significance in these instances. The sole exception is one of the AHC disorders, ALS, in which their presence is nearly mandatory for diagnosis. The most common situation in which fasciculation potentials appear, however, is the benign fasciculation syndrome. As its name implies, this disorder (if it can be designated as such) consists solely of an otherwise healthy person's experiencing widespread, persistent fasciculations, and often cramps as well. (Because both fasciculations and cramps are caused by muscle membrane irritability, they often are seen together) (5,9,13).