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Tourette syndrome

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For the Nirvana song, see tourette's (song)
For the Heavy Metal band, see Tourettes (band)
Tourette syndrome
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Tourette syndrome (also called Tourette's syndrome, Tourette's disorder, Gilles de la Tourette syndrome, GTS or TS) is an inherited neurological disorder with onset in childhood, characterized by the presence of multiple motor tics and at least one phonic tic, which characteristically wax and wane. Tourette's syndrome occurs along a spectrum of tic disorders, which includes transient tics and chronic tics.

Tourette syndrome was once considered a rare and bizarre syndrome. It is no longer considered rare, but is often undetected because of the wide range of severity, with most cases classified as mild.

The eponym was bestowed by Jean-Martin Charcot after and on behalf of his resident, Georges Albert Édouard Brutus Gilles de la Tourette, (1859 - 1904), a French physician and neurologist, who published an account of nine patients with Tourette's in 1885. Another French doctor, Jean Marc Gaspard Itard, reported the first case of Tourette syndrome in 1825, describing Marquise de Dampierre, an important woman of nobility in her time. [1]

Description

The hallmarks of Tourette's syndrome are repetitive, involuntary movements (motor tics) and utterances (phonic tics) that constantly change in number, frequency, severity, and anatomical location. The Tourette Syndrome Association describes tics as movements or sounds "that occur intermittently and unpredictably out of a background of normal motor activity".[2] The tics of Tourette's characteristically come and go. Waxing and waning — a natural increase and decrease in severity and frequency of tics — occurs differently in each individual. Tics are described as occurring in "bouts of bouts", which vary for each person.[3]

Coprolalia (the spontaneous utterance of socially objectionable or taboo words or phrases) is the most publicized symptom of Tourette's syndrome, but it is not required for a diagnosis of Tourette's. Fewer than 15% of TS patients exhibit coprolalia.[4] More common tics are eye blinking, throat clearing, coughing, neck stretching, and shoulder shrugging.

In contrast to the stereotyped movements of some other movement disorders (e.g.; choreas, dystonias, myoclonus, and dyskinesias), the tics of Tourette's are temporarily suppressible and preceded by a premonitory urge.[3] Immediately preceding tic onset, most individuals with TS are aware of a premonitory urge,[5] which is similar to the need to sneeze or scratch an itch. Individuals describe the need to tic as the buildup of tension in a particular anatomical location,[6] which they consciously choose to release, as if the subject "had to do it".[7] Some 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. These urges and sensations, preceding the expression of the movement or vocalization as a tic, are referred to in Tourette's subjects as "premonitory sensory phenomena". Some published descriptions of the tics of Tourette's identify sensory phenomena as the core symptom of TS, even though they are not included in the diagnostic criteria.[8][9]

Due to the sensory nature of tics, they can be described as semi-voluntary or "unvoluntary", because they may be experienced as a voluntary response to an unwanted, premonitory urge. Tics are experienced as irresistible and must eventually be expressed. People with TS are sometimes able to suppress their tics to some extent for limited periods of time, but doing so often results in an explosion of tics afterward. The control which can be exerted (from seconds to hours at a time) may merely postpone and exacerbate the ultimate expression of the tic. People with TS may seek a secluded spot to release their symptoms after suppressing them in school or at work. Some people with TS 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. They may have tics for several years before becoming aware of premonitory urges. Children may suppress tics while in the doctor's office, so they may need to be observed while they are not aware they are being watched. The ability to suppress tics varies among individuals, and may be more developed in adults than children.[10]

Tourette syndrome patients may exhibit symptoms of other conditions along with their motor and phonic tics. Associated conditions include attention-deficit hyperactivity disorder (ADD or ADHD), obsessive-compulsive disorder (OCD), learning disabilities and sleep disorders.[11] Disruptive behaviors, overall functioning, and cognitive function in patients with co-occurring Tourette's syndrome and ADHD may be accounted for by the comorbid ADHD, highlighting the importance of identifying and treating co-occurring conditions when they are present.[12][13][14][15]

Diagnosis

According to the DSM-IV-TR, TS is indicated when a person exhibits both multiple motor and one or more vocal tics (although these do not need to be concurrent) over the period of 1 year, with no more than 3 consecutive tic-free months. Previous versions of the Diagnostic and Statistical Manual of Mental Disorders (DSM) included a requirement for distress or impairment in social, occupational, or other important areas of functioning, but this requirement has been removed from the most recent version of the DSM, in recognition that not everyone with the diagnosis has distress or impairment to functioning. The onset must have been before the age of 18, and cannot be attributed to the use of a substance or another medical condition.[16] Hence, other medical conditions which include tics or tic-like movements (such as autism) must be ruled out before conferring a Tourette's diagnosis.

Although there is no such thing as a "typical" case, and each individual is different, Tourette's syndrome follows a fairly typical and reliable course in terms of age of onset and the natural time course of severity of symptoms. Tics may appear up to the age of 18, but the most typical age of onset is six or seven. The ages of statistical highest tic severity are 8 to 12 (average 10), with tics steadily declining for most patients as they pass through adolescence.[17] The most common, first-presenting tics are eye blinking, facial movements, sniffing and throat clearing. Tics most frequently present initially in midline body regions where there are many muscles: the head, neck and facial region.[10] This can be contrasted with the stereotyped movements of other disorders (e.g.; stims and stereotypies) which tend to have an earlier age of onset, are more symmetrical, and involve extremities (e.g.; flapping hands). [18] The most common tics to appear early in the course of the condition are frequently confused with other conditions: examples are allergies, asthma, and vision problems.[10]

There are no medical or screening tests which can be used in diagnosing Tourette's disorder. The diagnosis is made based on a history of symptoms, and after ruling out other conditions which can include tics.[4] If a physician believes that there may be another condition present which could explain tics, some tests may be ordered as necessary to rule out those other conditions. An example of this would be when diagnostic confusion between tics and seizure activity exists, which would call for an EEG, or if there are indications that an MRI is warranted to rule out brain abnormalities. However, most cases are diagnosed by merely observing a history of tics, and medical tests are not always called for.[10][4]

Because co-occurring conditions like OCD or attention-deficit hyperactivity disorder can be more impairing than tics, these conditions should be included in an evaluation of patients presenting with tics.[10][19] "It is critical to note that the comorbid conditions may determine functional status more strongly than the tic disorder." [10]

Differential diagnosis

Dystonias, choreas, other genetic conditions, and secondary causes of tics should be ruled out in the differential diagnosis for Tourette's syndrome.[19] Other conditions which may manifest tics or stereotyped movements include developmental disorders (autism spectrum disorders) and Stereotypic movement disorder;[20] other genetic conditions such as Huntington's disease, Neuroacanthocytosis, Hallervorden-Spatz disease, Idiopathic dystonia, Duchenne's disease, Tuberous sclerosis, Chromosomal disorders, Down syndrome, Klinefelter's syndrome, XYY karyotype, and Fragile X syndrome; Wilson's disease or Syndenham's chorea; and secondary or acquired causes of tics, such as drug-induced tics, head trauma, encephalitis, stroke, and carbon monoxide poisoning. Secondary causes of tics (not related to inherited Tourette's syndrome) are commonly referred to as tourettism. [19][21] The symptoms of Lesch-Nyhan syndrome may also be confused with Tourette syndrome. 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. [10]

Prognosis

Tourette's syndrome is a spectrum disorder, which means that the severity of the condition can range along a continuum from mild to severe. However, it should be emphasized that "the majority of cases can be categorized as mild." [22] Those with mild cases may be minimally impacted by symptoms, to the extent that casual observers might not know of their condition. Severe cases (which are the rare minority in adulthood) can inhibit or prevent the individual from engaging in common activities such as holding a job or having a fulfilling social life.

Regardless of symptom severity, individuals with TS can expect to live a normal life span. Although TS symptoms may be lifelong and chronic for some, it is not a degenerative condition and is not life-threatening. Life span and intelligence are normal, although learning disabilities may be present.[4]

Multiple studies have demonstrated that the condition in most children improves with maturity. Tics may be at their highest severity at the time that they are brought to diagnostic awareness, and often improve with understanding of the condition. The statistical age of highest tic severity is typically between 8 and 12, with most individuals experiencing steadily declining tic severity as they pass through adolescence. One study showed no correlation with tic severity and the onset of puberty, in contrast to the popular belief that tics increase at puberty. In many cases, complete remission of tic symptoms occurs after adolescence.[17] [23][24]

It is not uncommon for parents of affected children to be unaware that they, too, may have had tics as children. Because Tourette's syndrome tends to remit or subside in severity as one matures, and because milder cases of Tourette's are now more likely to be recognized, the first realization that a parent had tics as a child may not come until their offspring are diagnosed. It is not uncommon for several members of a family to be diagnosed together, as parents bringing children to a physician for an evaluation of tics come to the realization that, "I did that, too, as a child."

Children with Tourette's may suffer socially if their tics are viewed as "bizarre". If a child has disabling tics, or tics which interfere with social or academic functioning, supportive psychotherapy or school accommodations can be helpful. [4] Because co-occurring conditions (such as ADHD or OCD) can cause more impact on overall functioning than tics, a thorough evaluation for co-occurring conditions is called for when symptoms and impairment warrant. [19]

A supportive environment and family generally gives one skills to manage the disorder. Persons with Tourette's syndrome may learn to camouflage socially inappropriate tics or channel the energy of their tics into some other endeavor, to their advantage. Accomplished musicians, athletes, public speakers, and professionals from all walks of life are found among people with Tourette's syndrome.

There is currently no reliable means of predicting the outcome for any individual. The gene or genes for Tourette's syndrome have not been identified, and there is no potential "cure".[4]

Discussions with adults who have Tourette syndrome reveal that not everyone wants treatment or a "cure", especially if that means they may "lose" something else in the process. Some believe that there may even be latent advantages associated with the genetic vulnerability. [3]

Prevalence

Tourette's syndrome has historically been described as a rare disorder, with about 5 to 10 people in 10,000 having TS.[10] However, multiple studies published since 2000 demonstrate that the prevalence is much higher than previously thought, and that Tourette's syndrome can no longer be considered rare. Contemporary prevalence estimates range from 1 to 3 per 1,000[25] to 10 per 1,000.[26] A large, community-based study suggested that over 19% of school-age children have tics, with almost 4% of children in regular education fulfilling the diagnostic criteria for Tourette's Syndrome. The children with tic disorders in that study were usually undiagnosed.[27] As many as 1 in 100 people may experience some form of tic disorder, which includes transient tics, chronic tics, or Tourette's Syndrome.[11] Males are affected 3 to 4 times more often than females.[11][22] The disorder is frequently misdiagnosed or underdiagnosed, partly because of the wide expression of severity, ranging from mild (the majority of cases) or moderate, to severe (the rare, but more widely-recognized and publicized cases). Because the tics of Tourette's syndrome tend to remit or subside with maturity, such that a diagnosis may no longer be warranted for many adults, prevalence rates in pediatric populations are higher than those in adult populations.[17]

Tourette syndrome is found among all social, racial and ethnic groups.[11][28]

Causes and origins: genetic and epigenetic factors

Main article: Causes and origins of Tourette syndrome

Genetic studies have proven that the overwhelming majority of cases of Tourette's syndrome are inherited, although the exact mode of inheritance is not yet known. [28] Tic disorders have long been thought to be inherited as an autosomal dominant gene. Recent research challenges the autosomal dominant hypothesis, and suggests an additive model involving multiple genes.[10][19] In some cases, tics may not be inherited; these cases are identified as "sporadic" TS (also known as tourettism) because a genetic link is missing.[21]

Tourette's is a condition of incomplete penetrance, meaning not everyone who inherits the genetic vulnerability will show symptoms; Tourette's also shows variable expression — even family members with the same genetic makeup may show different levels of symptom severity. The gene(s) may express as TS, as a milder tic disorder (transient or chronic tics), or as obsessive compulsive symptoms with no tics at all. Only a minority of the children who inherit the gene(s) will have symptoms severe enough to ever require medical attention.[4] There is currently no way to predict the symptoms a child may display, even if the gene(s) are inherited.

A person with TS has about a 50% chance of passing the gene(s) to one of his/her children. Gender appears to have a role in the expression of the genetic vulnerability, with males more likely to express tics than females.[10] The exact mechanism affecting the inherited vulnerability has not been established. Research presents considerable evidence that abnormal activity of the brain chemical, or neurotransmitter, dopamine, is involved. Other neurotransmitters may also be involved.[4] Neuroanatomic models implicate failures in circuits connecting the brain's cortex and subcortex.[10]

Studies suggest that non-genetic, environmental, infectious, or psychosocial factors — while not causing Tourette's — can influence the severity of the disorder.[10] For example, twin studies have shown that the lower birth weight is more likely to have more noticeable symptoms.[29] Other perinatal events, such as maternal stress[30] and obstetric complications[31] may impact upon the severity of the expression of the inherited genetic vulnerability. Autoimmune processes may affect tic onset and exacerbation in some cases: the unproven and contentious hypothesis that pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections, P.A.N.D.A.S., plays a role in the onset of tic disorders and OCD is a current focus of research.

In clinical (referred) samples, OCD and ADHD are often associated with Tourette's. Some forms of OCD may be genetically linked to Tourette's.[32] "...at least some forms of OCD are etiologically related to TS, and may, therefore, be a variant expression of the same etiologic factors that are important for the expression of tics." [18] The genetic relationship of ADHD to Tourette's syndrome has not been fully established.[3] Not all persons with Tourette's syndrome will have ADHD or OCD, although in clinical populations, a high percentage of patients presenting for care do have ADHD. [19]

Treatment

Main article: Treatment of Tourette syndrome

Treatment of Tourette syndrome can be divided into treatment of tics, and treatment of co-occurring conditions, which, when present, are often a larger source of impairment than the tics themselves. Not all persons with tics will also have co-occurring conditions, but when comorbid disorders are present, they often take treatment priority. Knowledge and understanding are the best treatments available for tics. The majority of people with TS require no medication, but medication is available to help when symptoms interfere with functioning. Because children with tics often present to physicians when their tics are at their highest severity, and because of the waxing and waning nature of tics, it is recommended that medication not be started immediately or changed often. Frequently, the tics subside with understanding of the condition and a supportive environment.

The classes of medications with the most proven efficacy in treating tics — typical and atypical neuroleptics — can have long-term and short-term adverse effects.[19] The antihypertensive agents, clonidine (Catapres®) and guanfacine (Tenex®), are also used to treat tics. Stimulants and other medications may be useful in treating ADHD when it co-occurs with tic disorders. Drugs from several other classes of medications can be used as alternatives when stimulant trials fail. Clomipramine (Anafranil®), a tricyclic antidepressant, and SSRIs, a class of antidepressants including fluoxetine, sertraline, and fluvoxamine, may be prescribed when a TS patient also has symptoms of Obsessive-compulsive disorder.

Cognitive Behavioral Therapy (CBT) is a useful treatment when OCD is present, and there is increasing evidence supporting the use of habit reversal in the treatment of tics. Relaxation techniques, such as exercise, yoga or meditation, may also be useful in relieving stress that may aggravate tics.

Research directions and controversies

The direction of current and future research in Tourette's syndrome was delineated in a 2005 journal article [33] by the outgoing chairman of the TSA Scientific Advisory Board. Swerdlow divides the research landscape into five broad questions about Tourette's: "what is it, who has it, what causes it, how do we study it, and how do we treat it"?

According to Swerdlow,[33] "we still lack consensus on the definition of TS." He calls this "the 'core' TS conundrum". Since vocal tics result from a "motor event (ie, a contracting diaphragm moving air through the upper airways)", TS could be defined as a disorder of motor tics, eliminating the distinction between TS and the other tic disorders. Because "individuals with tics alone may not be functionally impaired", should TS, as currently defined, be a DSM diagnosis? Swerdlow highlights the importance of studies in new areas, such as behavioral techniques, and that "the whole-cloth dismissal of psychologic forces in the pathobiology of TS was a strategic error". Questions remain about whether co-occurring conditions should be part of the core definition, and why sensory phenomena, which are a core part of Tourette's, are not part of the diagnostic criteria.

Dropping the criteria for impairment from the diagnosis resulted in higher prevalence estimates for TS (the question of "who has it?"). With TS prevalence estimates at 1% to 2%, the condition is cast in an entirely new light.

Discovering "what causes TS" may resolve the questions of what it is and who has it. Research has been affected by the problem of referred samples, which may not reflect broader populations of persons with Tourette's. Probabilistic models may yield better results in finding the cause, as the autosomal dominant inheritance model has not been validated. The P.A.N.D.A.S. controversy remains contentious.

Expanding criteria for the diagnosis, and increasing awareness of the impact of co-occurring diagnoses result in further questions of how to study Tourette's. Developing and applying standardized instruments, along with awareness of ascertainment bias in recruitment sources, will be important in genetic studies. We don't know if "we lose both signals and are just adding noise to the experimental outcome"[33] when co-occurring conditions, such as OCD or ADHD, are included or excluded from study samples, or samples include/exclude children or adults, or patients with severe symptoms.

Tourette's is a heterogeous condition, with waxing and waning symptoms. The inherent changing nature of its core symptoms complicates research design. Results from case studies may not be borne out by controlled studies, stimulants may be under utilized, and behavioral therapies are understudied. High profile media coverage focuses on treatments that do not have established safety or efficacy e.g.; deep brain stimulation.

Sociological and cultural aspects

Main article: Sociological and cultural aspects of Tourette syndrome

With the increased knowledge of the full range of symptomatology of Tourette's syndrome, it has shifted from a condition only recognized in its most severe and impairing forms, to being recognized as a condition which is often mild, and which may be associated with some advantages and disadvantages. There are many individuals with Tourette's, living and deceased, recognized in their fields, or for whom obsessive-compulsive tendencies associated with Tourette's may have helped fuel their success. The best known example of a person who may have used obsessive-compulsive traits to advantage is Dr Samuel Johnson, lexicographer, who certainly had Tourette syndrome as evidenced by the writings of James Boswell.[34] Johnson wrote A Dictionary of the English Language in 1747, and was a prolific writer, poet, and critic. There are numerous recognized athletes, musicians, and authors with Tourette's.

Some authors have speculated that Mozart may have had Tourette syndrome.[35][36] However no Tourette's syndrome expert or organization has voiced concurrence that there is credible evidence to conclude that Mozart had Tourette's.[37]

The entertainment industry often depicts those with TS as being social misfits whose only tic is coprolalia, which has furthered stigmatization and the general public's misunderstanding of persons with Tourette's. The symptoms of Tourette syndrome are fodder for radio and television talk shows. Many television shows have addressed the topic of Tourette's, but often, television and film productions are not accurate representations of the condition, and many of them have used misconceptions about coprolalia as a plot device, or portrayed people with Tourette's as being dangerously out of control.

References


See also

Video clips of tics

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  2. ^ Tourette Syndrome Association. Definitions and Classification of Tic Disorders. Accessed 22 Mar 2005.
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  4. ^ a b c d e f g h Tourette Syndrome Association. Tourette Syndrome: Frequently Asked Questions Accessed 8 Feb 2006.
  5. ^ 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
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  7. ^ Kwak C, Dat Vuong K, Jankovic J. Premonitory sensory phenomenon in Tourette's syndrome. Mov Disord. 2003 Dec;18(12):1530-3. PMID 14673893
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  12. ^ Sukhodolsky DG, Scahill L, Zhang H, et al. Disruptive behavior in children with Tourette's syndrome: association with ADHD comorbidity, tic severity, and functional impairment. J Am Acad Child Adolesc Psychiatry. 2003 Jan;42(1):98-105. PMID 12500082
  13. ^ Hoekstra PJ, Steenhuis MP, Troost PW, et al. Relative contribution of attention-deficit hyperactivity disorder, obsessive-compulsive disorder, and tic severity to social and behavioral problems in tic disorders. J Dev Behav Pediatr. 2004 Aug;25(4):272-9. PMID 15308928
  14. ^ Carter AS, O'Donnell DA, Schultz RT, et al. Social and emotional adjustment in children affected with Gilles de la Tourette's syndrome: associations with ADHD and family functioning. Attention Deficit Hyperactivity Disorder. J Child Psychol Psychiatry. 2000 Feb;41(2):215-23. PMID 10750547
  15. ^ Spencer T, Biederman J, Harding M, et al. Disentangling the overlap between Tourette's disorder and ADHD. J Child Psychol Psychiatry. 1998 Oct;39(7):1037-44. PMID 9804036
  16. ^ Behavenet.Tourette's disorder. Accessed 10 Mar 2005.
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  18. ^ a b Cohen, DJ, Jankovic J, Goetz CG, (eds). Advances in Neurology, Vol. 85, Tourette Syndrome. Lippincott, Williams & Wilkins, Philadelphia, PA, 2001.
  19. ^ a b c d e f g Bagheri MM, Kerbeshian J, Burd L. Recognition and management of Tourette's syndrome and tic disorders. Am Fam Physician. 1999; 59:2263-2274.
  20. ^ Freeman, RD. Tourette's Syndrome: minimizing confusion. Accessed 8 February 2006.
  21. ^ a b Mejia NI, Jankovic J. Secondary tics and tourettism. Rev Bras Psiquiatr. 2005;27(1):11-7. PMID 15867978
  22. ^ a b Tourette Syndrome Association. What is Tourette syndrome? Accessed 11 Feb 2005.
  23. ^ Bloch MH, Peterson BS, Scahill L, et al. Adulthood outcome of tic and obsessive-compulsive symptom severity in children with Tourette syndrome. Arch Pediatr Adolesc Med. 2006;160(1):65-69. PMID 16389213
  24. ^ Burd L, Kerbeshian PJ, Barth A, et al. Long-term follow-up of an epidemiologically defined cohort of patients with Tourette syndrome. J Child Neurol. 2001;16(6):431-437. PMID 11417610
  25. ^ Scahill L, Tanner C, Dure L. The epidemiology of tics and Tourette syndrome in children and adolescents. Adv Neurol. 2001;85:261-71. PMID 11530433
  26. ^ Kadesjo B, Gillberg C. Tourette's disorder: epidemiology and comorbidity in primary school children. J Am Acad Child Adolesc Psychiatry. 2000 May;39(5):548-55. PMID 10802971
  27. ^ Kurlan R, McDermott MP, Deeley C, et al. Prevalence of tics in schoolchildren and association with placement in special education. Neurology. 2001 Oct 23;57(8):1383-8. PMID 11673576
  28. ^ a b Robertson MM. Tourette syndrome, associated conditions and the complexities of treatment. Brain. 2000;123 Pt 3:425-462. PMID 10686169
  29. ^ Hyde TM, Aaronson BA, Randolph C, et al. Relationship of birth weight to the phenotypic expression of Gilles de la Tourette's syndrome in monozygotic twins. Neurology. 1992 Mar;42 (3 Pt 1):652-8. PMID 1549232
  30. ^ Leckman JF, Dolnansky ES, Hardin MT, et al. Perinatal factors in the expression of Tourette's syndrome: an exploratory study. J Am Acad Child Adolesc Psychiatry. 1990 Mar;29(2):220-6. PMID 1969861
  31. ^ Santangelo SL, Pauls DL, Goldstein JM, et al. Tourette's syndrome: what are the influences of gender and comorbid obsessive-compulsive disorder? J Am Acad Child Adolesc Psychiatry. 1994 Jul-Aug;33(6):795-804. PMID 8083136
  32. ^ Pauls DL, Towbin KE, Leckman JF, et al. Gilles de la Tourette's syndrome and obsessive-compulsive disorder. Evidence supporting a genetic relationship. Arch Gen Psychiatry. 1986 Dec;43(12):1180-2. PMID 3465280
  33. ^ a b c Swerdlow, NR. Tourette Syndrome: Current Controversies and the Battlefield Landscape. Curr Neurol Neurosci Rep. 2005, 5:329-331. PMID 16131414
  34. ^ Tourette Syndrome Association. Samuel Johnson. Accessed 10 February 2005.
  35. ^ Simkin, Benjamin. Medical and Musical Byways of Mozartiana. FITHIAN PRESS.
  36. ^ Simkin B. Mozart's scatological disorder. BMJ. 1992 Dec 19-26;305(6868):1563-7. PMID 1286388
  37. ^ Tourette Syndrome Association:Did Mozart really have TS? Accessed online 14 Aug 2002.
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