A fasciculation //, or "muscle twitch", is a small, local, involuntary muscle contraction and relaxation which may be visible under the skin or detected in deeper areas by EMG testing. They arise as a result of spontaneous depolarization of a lower motor neuron leading to the synchronous contraction of all of the skeletal muscle fibers within a single motor unit. Fasciculations can happen in any skeletal muscle in the body. Fasciculations have a variety of causes, the majority of which are benign, but can also be due to disease of the motor neurons. Fasciculations are commonly encountered in healthy people and are rarely bothersome. In some cases the presence of fasciculations can be annoying and interfere with quality of life. In such cases, where the remainder of the neurological exam is normal, and EMG testing does not indicate any additional pathology a diagnosis of benign fasciculation syndrome is usually made.
Risk factors 
||This article may contain original research. (December 2011)|
Pathological conditions 
- Neuromyotonia, also known as Isaacs' syndrome
- Diseases of the lower motor neuron including:- Poliomyelitis, Spinomuscular atrophy or SMA group of diseases including Werdnig-Hoffman disease, Amyotrophic lateral sclerosis (ALS), Kennedy disease
- Organophosphate poisoning (e.g. insecticides) or use of acetylcholinesterase inhibitors (commonly used in Myasthenia Gravis)
- Benzodiazepine withdrawal
- Magnesium deficiency
- Myalgic Encephalomyelitis
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 ALS.
Other risk factors may include the use of anticholinergic drugs over long periods, in particular ethanolamines such as Benadryl, used as an antihistamine and sleep aid, and Dramamine for nausea and motion sickness. Persons with benign fasciculation syndrome (BFS) may experience paraesthesia shortly after taking such medication; fasciculation episodes begin as the medication wears off.
Stimulants can cause fasciculations directly. These include caffeine, pseudoephedrine (Sudafed), amphetamines, and the asthma bronchodilators salbutamol (e.g. Proventil, Combivent, Ventolin). Medications used to treat attention deficit disorder often contain stimulants as well, and are common causes of benign fasciculations.
The depolarizing neuromuscular blocker, succinylcholine, causes fasciculations. It is a normal side effect of the drug's administration, and can be prevented with a small dose of a nondepolarizing neuromuscular blocker prior to the administration of succinylcholine, often 10% of a nondepolarizing NMB's induction dose.
Inadequate magnesium intake can cause fasciculations, especially after a magnesium loss due to severe diarrhea. Over-exertion is another risk factor for magnesium loss. As 70-80% of the adult population does not consume the recommended daily amount of magnesium, inadequate intake may also be a common cause. Treatment consists of increased intake of magnesium from dietary sources such as nuts (especially almonds) and bananas. Magnesium supplements or pharmaceutical magnesium preparations may also be taken. However, too much magnesium may cause diarrhea, resulting in dehydration and nutrient loss (including magnesium itself, leading to a net loss, rather than a gain). Chelated magnesium can help reduce this effect.
Fasciculation also often occurs during a rest period after sustained stress, such as that brought on by unconsciously tense muscles. Reducing stress and anxiety is therefore another useful treatment.
There is no proven treatment for fasciculations in people with ALS. Among patients with ALS, fasciculation frequency is not associated with the duration of ALS and is independent of the degree of limb weakness and limb atrophy. No prediction of ALS disease duration can be made based on fasciculation frequency alone.
See also 
- Blexrud MD, Windebank AJ, Daube JR (1993). "Long-term follow-up of 121 patients with benign fasciculations". Ann. Neurol. 34 (4): 622–5. doi:10.1002/ana.410340419. PMID 8215252.
- "Strength, physical activity, and fasciculations in patients with ALS." Amyotroph Lateral Scler. 9(2):120-1. PMID 18428004.
- Galan P, Preziosi P, Durlach V, Valeix P, Ribas L, Bouzid D, Favier A, Hercberg S (1997). "Dietary magnesium intake in a French adult population." Magnesium Research 10(4):321-8. PMID 9513928.
- Mateen FJ, Sorenson EJ, Daube JR (2008). "Strength, physical activity, and fasciculations in patients with ALS." Amyotroph Lateral Scler. 9(2):120-1. PMID 18428004.