View source for Fasciculation

{{Short description|Spontaneous, involuntary muscle twitch}}
{{more medical citations needed|date=July 2020}}
{{Infobox medical condition (new)
| name            = Fasciculation
| synonyms        = Muscle twitch
|image         = Bfs spasm.gif
 |image_size    =
 |alt           = Animated image showing involuntary twitching in the upper eyelid of a young adult male
 |caption       = Animated image showing involuntary twitching in the upper eyelid of a young adult male
| pronounce       = {{IPAc-en|f|ə|ˌ|s|ɪ|k|j|ʊ|ˈ|l|eɪ|ʃ|ən}}
| field           = [[Neurology]]
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A '''fasciculation''', or '''muscle twitch''', is a spontaneous, involuntary [[muscle contraction]] and relaxation, involving fine muscle fibers.<ref name= Blackman2019>{{cite journal |vauthors=Blackman G, Cherfi Y, Morrin H, ''et al'' |title=The association between benign fasciculations and health anxiety: a report of two cases and a systematic review of the literature |journal=Psychosomatics |volume=60 |issue=5 |pages=499–507 |date=2019 |pmid=31174866 |doi=10.1016/j.psym.2019.04.001 |s2cid=146012381 |url= https://discovery.ucl.ac.uk/id/eprint/10076229/3/David_The%20Association%20Between%20Benign%20Fasciculations%20and%20Health%20Anxiety_AAM.pdf}}</ref> They are common, with as many as 70% of people experiencing them.<ref name= Blackman2019/> They can be benign, or associated with more serious conditions.<ref name= Blackman2019/>  When no cause or pathology is identified, they are diagnosed as [[benign fasciculation syndrome]].<ref name= Blackman2019/>

==Diagnosis==
{{further|Benign fasciculation syndrome}}
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]]<ref name=pmid18428004>{{cite journal |vauthors=Mateen FJ, Sorenson EJ, Daube JR |title=Strength, physical activity, and fasciculations in patients with ALS |journal=Amyotrophic Lateral Sclerosis |volume=9 |issue=2 |pages=120–1 |year=2008 |pmid=18428004 |doi=10.1080/17482960701855864 |s2cid=43321868 }}</ref> (ALS).

Deeper areas of contraction can be detected by electromyography (EMG) testing, though they can happen in any [[skeletal muscle]] in the body. Fasciculations arise as a result of [[depolarization|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.

[[Tics]] must also be distinguished from fasciculations. Small twitches of the upper or lower eyelid, for example, are not tics, because they do not involve a whole muscle, but rather are unsuppressible twitches of a few muscle fibre bundles.<ref>
{{cite journal|url= https://d1wqtxts1xzle7.cloudfront.net/62154985/22._TIC_10.1920200220-73731-xvf2fo.pdf?1582237254=&response-content-disposition=inline%3B+filename%3DTic_disorder_definition_clinical_context.pdf&Expires=1594852037&Signature=M5jspfaapRSdO3HtflIOLfUA1LTFzYnhBpyq5WKoNWvzokN-ZBxxGQupdgroalVSF7iBch5mBOygBYllUqPrCV1KRaVVUd-MWHovSHFFjnEGVdW-2sdHUQXejhXVx-0DfMZVufscBG7Dvl~4dR8u50E0KAECaP69SxN2aaA3Q3Vpf3ivoOCU9fj8WqxUsqJgelEnq6smwiXU5zujC90xyDvetTTfJYZweNEobMH-cqY0sTMjWXmH~-mCX8O6SKa0Lf1RdvDgXO-FLPml36Zf20sD6RR8IO1poxgtPsIrZ632qJL23ELOQTnDwUUNDkNBnz0YJU6hyxFLTGYBy0mz1w__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA |archive-url= https://web.archive.org/web/20200715213358/https://d1wqtxts1xzle7.cloudfront.net/62154985/22._TIC_10.1920200220-73731-xvf2fo.pdf?1582237254=&response-content-disposition=inline%3B+filename%3DTic_disorder_definition_clinical_context.pdf&Expires=1594852037&Signature=M5jspfaapRSdO3HtflIOLfUA1LTFzYnhBpyq5WKoNWvzokN-ZBxxGQupdgroalVSF7iBch5mBOygBYllUqPrCV1KRaVVUd-MWHovSHFFjnEGVdW-2sdHUQXejhXVx-0DfMZVufscBG7Dvl~4dR8u50E0KAECaP69SxN2aaA3Q3Vpf3ivoOCU9fj8WqxUsqJgelEnq6smwiXU5zujC90xyDvetTTfJYZweNEobMH-cqY0sTMjWXmH~-mCX8O6SKa0Lf1RdvDgXO-FLPml36Zf20sD6RR8IO1poxgtPsIrZ632qJL23ELOQTnDwUUNDkNBnz0YJU6hyxFLTGYBy0mz1w__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA |url-status= dead |archive-date= 2020-07-15 |title= Tic disorder: definition, clinical contexts, differential diagnosis, neural correlates and therapeutic approaches |publisher= MeDOA Publications |journal= Journal of Neuroscience and Rehabilitation |date= 2019 |volume=  2019 |issue= 1 |vauthors= Perrotta G |quote= Tics must also be distinguished from fasciculations. Small contractions of the upper or lower eyelid, for example, are not tics, because they do not involve an entire muscle. They are contractions of some bundles of muscle fibres, which can be felt but just seen. These contractions of the eyelids also differ from tics in that they are not suppressible, are strictly involuntary and tend to fade after a day or two.}}</ref>

==Causes==

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 up to 70% of all healthy people,<ref name= Blackman2019/> 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.<ref>{{Cite journal|last1=Filippakis|first1=Alexandra|last2=Jara|first2=Jordan|last3=Ventura|first3=Nick|last4=Ruthazer|first4=Robin|last5=Russell|first5=James|last6=Ho|first6=Doreen|date=2017-04-18|title=A Prospective Study of Benign Fasciculation Syndrome (S45.007)|url=https://n.neurology.org/content/88/16_Supplement/S45.007|journal=Neurology|language=en|volume=88|issue=16 Supplement|doi=10.1212/WNL.88.16_supplement.S45.007 |s2cid=80074693 |issn=0028-3878|url-access=subscription}}</ref>

===Risk factors===
[[Risk factor]]s for benign fasciculations are age, stress, fatigue, and strenuous exercise.<ref name= Blackman2019/> Fasciculations can be caused by [[anxiety disorder|anxiety]], caffeine or alcohol and thyroid disease.<ref name= Turner2013>{{cite journal |vauthors=Turner MR, Talbot K |title=Mimics and chameleons in motor neurone disease |journal=Pract Neurol |volume=13 |issue=3 |pages=153–64 |date=June 2013 |pmid=23616620 |pmc=3664389 |doi=10.1136/practneurol-2013-000557 |type= Review}}</ref>

Other factors may include the use of [[anticholinergic]] drugs over long periods.{{citation needed|date=August 2016}} In particular, these include [[ethanolamine]]s such as [[diphenhydramine]] (brand names Benadryl, Dimedrol, Daedalon and Nytol), used as an [[antihistamine]] and [[sedative]], and [[dimenhydrinate]] (brand names Dramamine, Driminate, Gravol, Gravamin, Vomex, and Vertirosan) for [[nausea]] and [[motion sickness]]. Persons with [[benign fasciculation syndrome]] (BFS) may experience [[paraesthesia]] (especially [[numbness]]) shortly after taking such medication; fasciculation episodes begin as the medication wears off.

[[Stimulant]]s can cause fasciculations directly. These include [[caffeine]], [[pseudoephedrine]] (Sudafed), [[amphetamines]], and the [[asthma]] [[bronchodilator]] [[salbutamol]] (brand names Proventil [albuterol sulfate], Combivent [ipratropion bromide and salbutamol], Ventolin [albuterol sulfate]). Medications used to treat [[ADHD|attention deficit disorder]] (ADHD) often contain stimulants as well, and are common causes of benign fasciculations. Since asthma and ADHD are much more serious than the fasciculations themselves, this [[side effect]] may have to be tolerated by the patient after consulting a physician or pharmacist.

The depolarizing [[neuromuscular blocker]] [[succinylcholine]] causes fasciculations. It is a normal side effect of the drug's administration. It 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.

Even if a drug such as caffeine causes fasciculations, that does not necessarily mean it is the only cause. For example, a very slight [[Magnesium deficiency (medicine)|magnesium deficiency]] by itself (see below) might not be enough for fasciculations to occur, but when combined with caffeine, the two factors together could be enough.{{Citation needed|date=December 2024}}

==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.<ref name=pmid18428004/>

== Epidemiology ==
Fasciculations are observed more often in males, and clinicians are overrepresented in study samples.<ref name= Blackman2019/>

==See also==
* [[Blepharospasm]]
* [[Carnitine palmitoyltransferase II deficiency]]
* [[Myokymia]]
* [[Fibrillation]]
* [[Myoclonus]]
* [[Seizure]] and [[convulsion]]
* [[Tremor]]
* [[Twitch (disambiguation)]]

==References==
{{Reflist}}

== External links ==
{{Medical resources
|   DiseasesDB     = 18832
|   ICD10          =  {{ICD10|R|25|3|r|25}} 
|   ICD9           = {{ICD9|781.0}}
|   ICDO           =
|   OMIM           =
|   MedlinePlus    = 003296
|   eMedicineSubj  =
|   eMedicineTopic =
|   MeshID         = D005207
}}
{{Nervous and musculoskeletal system symptoms and signs}}

[[Category:Symptoms and signs: Nervous system]]