Muscle twitching

Fasciculation
Classification and external resources
Specialty	Neurology
ICD-10	R25.3
ICD-9-CM	781.0
DiseasesDB	18832
MedlinePlus	003296
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A fasciculation /fəˌsɪkjᵿˈleɪʃən/, or muscle twitch, is a small, local, involuntary muscle contraction and relaxation which may be visible under the skin. Deeper areas can be detected by electromyography (EMG) testing, though they can happen in any skeletal muscle in the body. Fasciculations arise as a result of spontaneous depolarization of a lower motor neuron leading to the synchronous contraction of all the skeletal muscle fibers within a single motor unit. An example of normal spontaneous depolarization is the constant contractions of cardiac muscle, causing the heart to beat. Usually, intentional movement of the involved muscle causes fasciculations to cease immediately, but they may return once the muscle is at rest again.

Fasciculations have a variety of causes, the majority of which are benign, but can also be due to disease of the motor neurons. They are encountered by virtually all healthy people, though for most, it is quite infrequent. In some cases, the presence of fasciculations can be annoying and interfere with quality of life. If a neurological examination is otherwise normal and EMG testing does not indicate any additional pathology, a diagnosis of benign fasciculation syndrome is usually made.

The most effective way to detect fasciculations may be surface electromyography (EMG). Surface EMG is more sensitive than needle electromyography and clinical observation in the detection of fasciculation in people with amyotrophic lateral sclerosis.

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