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{{otheruses|tic (disambiguation)}}
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A '''tic''' is a sudden, repetitive, nonrhythmic, stereotyped motor movement or vocalization involving discrete muscle groups.<ref name=phenomenology>Leckman JF, Bloch MH, King RA, Scahill L. "Phenomenology of tics and natural history of tic disorders". ''Adv Neurol.'' 2006;99:1–16. PMID 16536348</ref><ref name=BehaveNet> [[American Psychiatric Association]] (2000). [http://behavenet.com/capsules/disorders/touretteTR.htm DSM-IV-TR: Tourette's Disorder.] ''Diagnostic and Statistical Manual of Mental Disorders'', 4th ed., text revision ([[DSM-IV-TR]]), ISBN 0-89042-025-4. Available at BehaveNet.com Retrieved on August 10, 2009.</ref>   Tics can be invisible to the observer, such as abdominal tensing or toe crunching.  Common motor and phonic tics are, respectively, eye blinking and throat clearing.<ref>Malone DA Jr, Pandya MM. "Behavioral neurosurgery". ''Adv Neurol.'' 2006;99:241–47. PMID 16536372</ref> Movements of other [[movement disorder]]s (for example, [[chorea (disease)|chorea]], [[dystonia]], [[myoclonus]]) must be distinguished from tics. Other conditions, such as [[autism]] and [[stereotypic movement disorder]], also include movements which may be confused with tics. Tics must also be distinguished from the compulsions of [[Obsessive-compulsive disorder|OCD]] and from [[seizure]] activity.

== Description and classification ==
{{Clips of tics}}
Tics are classified as motor vs. phonic and simple vs. complex. 

'''Motor tics''' are movement-based tics affecting discrete muscle groups. 

'''Phonic tics''' are involuntary sounds produced by moving air through the nose, mouth, or throat. They may be alternately referred to as '''verbal tics''' or '''vocal tics''', but most diagnosticians prefer the term ''phonic tics'' to reflect the notion that the [[vocal cords]] are not involved in all tics that produce sound.<ref>Robertson MM. Tourette syndrome, associated conditions and the complexities of treatment. ''Brain''. 2000 Mar;123 Pt 3:425-62. PMID 10686169</ref>

Tics may increase as a result of [[Stress (medicine)|stress]], fatigue, boredom, or high-energy emotions, which can include negative emotions, such as [[anxiety]], but positive emotions as well, such as excitement or anticipation. Relaxation may result in a tic increase (for instance, watching television or using a computer), while concentration on an absorbing activity often leads to a decrease in tics.<ref>National Institutes of Health (NIH). [http://web.archive.org/web/20050323092424/http://www.ninds.nih.gov/disorders/tourette/detail_tourette.htm Tourette Syndrome Fact Sheet.] Retrieved on March 23, 2005.</ref><ref>Packer, L. [http://www.tourettesyndrome.net/tourette_primer4.htm Tourette Syndrome "Plus"]. Retrieved on February 12, 2006.</ref>  Neurologist and writer [[Oliver Sacks]] described a physician with severe [[Tourette syndrome]] (Canadian Mort Doran, M.D., a pilot and surgeon in real life, although a [[pseudonym]] was used in the book), whose tics remitted almost completely while he was performing surgery.<ref>Doran, Morton L. The Tourette Syndrome Association, Inc., Connecticut Chapter 1998 Educators' Conference; 1998 Nov 6; Danbury, CT.</ref><ref>Sacks O. ''[[An Anthropologist on Mars]]''. Knopf, New York, 1995.</ref>  

Immediately preceding tic onset, most individuals are aware of an urge<ref>Cohen AJ, Leckman JF. Sensory phenomena associated with Gilles de la Tourette's syndrome. ''J Clin Psychiatry''. 1992 Sep;53(9):319–23. PMID 1517194</ref> that is similar to the need to yawn, sneeze, blink, or scratch an itch. Individuals describe the need to tic as a buildup of tension<ref>Bliss J. Sensory experiences of Gilles de la Tourette syndrome. ''Arch Gen Psychiatry''. 1980 Dec;37(12):1343–47. PMID 6934713 </ref> that they consciously choose to release, as if they "had to do it".<ref>  Kwak C, Dat Vuong K, Jankovic J. "Premonitory sensory phenomenon in Tourette's syndrome". ''Mov Disord''. 2003 Dec;18(12):1530–33. PMID 14673893</ref>  Examples of this premonitory urge are the feeling of having something in one's throat or a localized discomfort in the shoulders, leading to the need to clear one's throat or shrug the shoulders. The actual tic may be felt as relieving this tension or sensation, similar to scratching an itch. Another example is blinking to relieve an uncomfortable sensation in the eye. 

Tics are described as semi-voluntary or ''unvoluntary'',<!-- Please do NOT CHANGE "UNVOLUNTARY" to "INVOLUNTARY"; it is not a typo, it is the correct term, please read the text and the references. --><ref name=TSADef>"The Tourette Syndrome Classification Study Group. Definitions and classification of tic disorders". ''Arch Neurol.'' 1993 Oct;50(10):1013–16. PMID 8215958 [http://web.archive.org/web/20060426232033/http://www.tsa-usa.org/research/definitions.html Full text], archived April 26, 2006.</ref> because they are not strictly ''involuntary''—they may be experienced as a ''voluntary'' response to the unwanted, premonitory urge. A unique aspect of tics, relative to other movement disorders, is that they are suppressible yet irresistible;<ref name=Dure>Dure LS 4th, DeWolfe J. Treatment of tics. ''Adv Neurol.'' 2006;99:191-96. PMID 16536366</ref> they are experienced as an irresistible urge that must eventually be expressed.<ref name=TSADef/>  Some people with tics may not be aware of the premonitory urge. Children may be less aware of the premonitory urge associated with tics than are adults, but their awareness tends to increase with maturity.<ref name=TSADef/> 

===Simple tics===

'''Simple motor tics''' are typically sudden, brief, meaningless movements that usually involve only one group of muscles, such as eye blinking, head jerking or shoulder shrugging.<ref name=SingerBehavior>Singer HS. "Tourette's syndrome: from behaviour to biology". ''Lancet Neurol.'' 2005 Mar; 4(3):149–59. PMID 15721825</ref>  Motor tics can be of an endless variety and may include such movements as hand clapping, neck stretching, mouth movements, head, arm or leg jerks, and facial grimacing. 

A '''simple phonic tic''' can be almost any sound or noise, with common vocal tics being throat clearing, sniffing, or grunting.<ref name=SingerBehavior/>

===Complex tics===
'''Complex motor tics''' are typically more purposeful-appearing and of a longer nature.  They may involve a cluster of movements and appear coordinated.<ref name=SingerBehavior/> Examples of complex motor tics are pulling at clothes, touching people, touching objects, [[echopraxia]] and [[copropraxia]]. 

'''Complex phonic tics''' may fall into various series (categories), including [[echolalia]] (repeating words just spoken by someone else), [[palilalia]] (repeating one's own previously spoken words), lexilalia (repeating words after reading them) and [[coprolalia]] (the spontaneous utterance of socially objectionable or taboo words or phrases). Coprolalia is a highly publicized symptom of [[Tourette syndrome]]; however, only about 10% of TS patients exhibit coprolalia.<ref name=SingerBehavior/>

Complex tics are rarely seen in the absence of simple tics. Tics "may be challenging to differentiate from compulsions",<ref>Scamvougeras, Anton. [http://ww1.cpa-apc.org:8080/publications/archives/bulletin/2002/february/specialfeaturescamvougeras.asp "Challenging Phenomenology in Tourette Syndrome and Obsessive–Compulsive Disorder: The Benefits of Reductionism".] Canadian Psychiatric Association (February 2002). Retrieved on June 5, 2007.</ref> as in the case of [[klazomania]] (compulsive shouting).

== Tic disorders ==
{{main|Tic disorder}}
Tic disorders occur along a spectrum, ranging from mild to more severe, and are classified according to duration and severity (transient tics, chronic tics, or Tourette syndrome). Tourette syndrome is the more severe expression of a spectrum of tic disorders, which are thought to be due to the same genetic vulnerability. Nevertheless, most cases of Tourette syndrome are not severe.<ref name=Zinner2000>Zinner SH. Tourette disorder. ''Pediatr Rev''. 2000 Nov;21(11):372-83. PMID 11077021</ref>  The treatment for the spectrum of tic disorders is similar to the [[treatment of Tourette syndrome]].

== Differential diagnosis ==
[[Dystonia]]s, choreas, other genetic conditions, and secondary causes of tics should be ruled out in the [[differential diagnosis]].<ref name=Bagheri/>  Conditions besides Tourette syndrome that may manifest tics or stereotyped movements include [[developmental disorder]]s, [[autism spectrum disorder]]s,<ref>Ringman JM, Jankovic J. "Occurrence of tics in Asperger's syndrome and autistic disorder".  ''J Child Neurol.'' 2000 Jun;15(6):394–400. PMID 10868783</ref> and [[stereotypic movement disorder]];<ref>Jankovic J, Mejia NI. "Tics associated with other disorders". ''Adv Neurol.'' 2006;99:61–8. PMID 16536352</ref><ref name=FreemanBlog>Freeman, RD.  [http://www.tourette-confusion.blogspot.com/ Tourette's Syndrome: minimizing confusion]. Roger Freeman, MD, blog. Retrieved on February 8, 2006.</ref>  [[Sydenham's chorea]]; [[idiopathic]] dystonia; and genetic conditions such as [[Huntington's disease]],  [[neuroacanthocytosis]], [[Hallervorden-Spatz syndrome]], [[Duchenne muscular dystrophy]], Wilson's disease, and [[tuberous sclerosis]]. Other possibilities include chromosomal disorders such as [[Down syndrome]], [[Klinefelter's syndrome]], [[XYY syndrome]] and [[fragile X syndrome]]. Acquired causes of tics include drug-induced tics, head trauma, [[encephalitis]], [[stroke]], and [[carbon monoxide poisoning]].<ref name=Bagheri/><ref name=Mejia>Mejia NI, Jankovic J. [http://www.scielo.br/pdf/rbp/v27n1/23707.pdf "Secondary tics and tourettism"] (PDF).  ''Rev Bras Psiquiatr''. 2005;27(1):11–17. PMID 15867978</ref> Most of these conditions are rarer than tic disorders, and a thorough history and examination may be enough to rule them out, without medical or screening tests.<ref name=Zinner2000/> 

Although tic disorders are commonly considered to be childhood syndromes, tics occasionally develop during adulthood; adult-onset tics often have a secondary cause.<ref>[http://cat.inist.fr/?aModele=afficheN&cpsidt=16202816 Adult-onset tic disorder, motor stereotypies, and behavioural disturbance associated with antibasal ganglia antibodies]</ref>  Tics that begin after the age of 18 are generally not considered symptoms of Tourette's syndrome. 

Tests may be ordered as necessary to rule out other conditions: for example, when diagnostic confusion between tics and [[seizure]] activity exists, an [[Electroencephalography|EEG]] may be ordered, or symptoms may indicate that an [[MRI]] is needed to rule out brain abnormalities.<ref name=Assessment>Scahill L, Erenberg G, Berlin CM Jr, Budman C, Coffey BJ, Jankovic J, Kiessling L, King RA, Kurlan R, Lang A, Mink J, Murphy T, Zinner S, Walkup J; Tourette Syndrome Association Medical Advisory Board: Practice Committee. "Contemporary assessment and pharmacotherapy of Tourette syndrome". ''NeuroRx.'' 2006 Apr;3(2):192–206.  PMID 16554257</ref>  [[Thyroid-stimulating hormone|TSH]] levels can be measured to rule out [[hypothyroidism]], which can be a cause of tics.  [[Brain imaging]] studies are not usually warranted.<ref name=Assessment/>  In teenagers and adults presenting with a sudden onset of tics and other behavioral symptoms, a [[Drug test#Urine drug screen|urine drug screen]] for [[cocaine]] and [[stimulants]] might be necessary. If a family history of [[liver disease]] is present, serum copper and [[ceruloplasmin]] levels can rule out [[Wilson's disease]].<ref name=Bagheri>Bagheri, Kerbeshian & Burd (1999).</ref> most cases are mild.<ref name=TSAWhat>[http://web.archive.org/web/20060524115004/http://www.tsa-usa.org/what_is/whatists.html What is Tourette syndrome?] [[Tourette Syndrome Association]]. Archived May 24, 2006.</ref>  

Tics must be distinguished from [[fasciculation]]s. Small twitches of the upper or lower eyelid, for example, are not tics, because they do not involve a whole muscle. They are twitches of a few muscle fibre bundles, which one can feel but barely see.<ref>Freeman, R. [http://www.tourette-confusion.blogspot.com/ Tourette syndrome:  minimizing confusion.]  Retrieved on February 18, 2006.</ref>

== Society and culture ==
There is some confusion in [[Sociological_and_cultural_aspects_of_Tourette_syndrome#References_in_the_entertainment_industry|media portrayals of tics]]; by sensationalizing the symptoms of Tourette's, the video media have contributed to warped perceptions about tics.

==Notes==
{{reflist|2}}

== Further reading ==
* Black, Kevin J. [http://www.emedicine.com/neuro/topic664.htm Tourette Syndrome and Other Tic Disorders.]
* Evidente, GH. [http://web.archive.org/web/20080731231002/http://www.postgradmed.com/issues/2000/10_00/evidente_tic.shtml "Is it a tic or Tourette's? Clues for differentiating simple from more complex tic disorders."] ''PostGraduate Medicine Online''. October 2000 108:5.
* Swerdlow, NR. "Tourette Syndrome: Current Controversies and the Battlefield Landscape". ''Curr Neurol Neurosci Rep''. 2005, 5:329-331. PMID 16131414
The Tourette Syndrome Classification Study Group. [http://web.archive.org/web/20050322170245/http://www.tsa-usa.org/research/definitions.html "Definitions and classification of tic disorders"]. ''Arch. Neurol.''  50 (10): 1013-6. PMID 8215958. Retrieved on 2005-03-22

{{Topics related to Tourette syndrome}}
{{Obsessive–compulsive disorder}}
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[[Category:Habits]]
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[[Category:Tourette syndrome]]

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