History of Tourette syndrome
Encyclopedia
Tourette syndrome
is an inherited
neurological disorder with onset in childhood, characterized by the presence of multiple physical (motor) tic
s and at least one vocal (phonic) tic.
The eponym
was bestowed by Jean-Martin Charcot
(1825–93) 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. The possibility that movement disorder
s, including Tourette syndrome, might have an organic origin was raised when an encephalitis
epidemic from 1918–1926 led to a subsequent epidemic of tic disorder
s. Research in 1972 advanced the argument that Tourette's is a neurological, rather than psychological
, disorder; since the 1990s, a more neutral view of Tourette's
has emerged, in which biological vulnerability and adverse environmental events are seen to interact.
Findings since 1999 have advanced TS science in the areas of genetics, neuroimaging
, neurophysiology
, and neuropathology
. Questions remain regarding how best to classify Tourette syndrome, and how closely Tourette's is related to other movement disorders or psychiatric
disorders. Good epidemiologic data is still lacking, and available treatments
are not risk free and not always well tolerated.
, reported the first case of Tourette syndrome in 1825, describing Marquise de Dampierre, an important woman of nobility in her time, whose episodes later understood to be coprolalia
"were obviously in stark contrast to the lady's background, intellect, and refined manners".
Jean-Martin Charcot, an influential French physician, assigned his resident Georges Albert Édouard Brutus Gilles de la Tourette, a French physician and neurologist, to study patients at the Salpêtrière
Hospital, with the goal of defining an illness distinct from hysteria
and from chorea. Charcot and Tourette believed that the "tic illness" they had observed was an untreatable, chronic, and progressive hereditary condition. History is unclear on whether Charcot had examined the Marquise de Dampierre, but his publications mention having met her socially and overhearing her most common utterances of "merde and foutu cochon (which translates literally as filthy pig but the truer colloquial meaning is 'fucking pig')".
In 1885, Gilles de la Tourette published an account of nine patients, Study of a Nervous Affliction, concluding that a new clinical category should be defined. His description included accounts of Marquise de Dampierre, previously described by Itard, as a reclusive aristocratic lady who "ticked and blasphemed" from the age of seven until her death at the age of 80 years. Gilles de la Tourette describes the common feature of involuntary movements or tics in all nine patients. The eponym was later bestowed by Charcot after and on behalf of Gilles de la Tourette.
Little progress was made over the next century in explaining or treating tics. With limited clinical experience, involving typically one or two patients, authors advanced different ideas, including brain
lesion
s similar to those resulting from rheumatic chorea
or encephalitis lethargica
as a cause of tics, faulty mechanisms of normal habit
formation, and treatment with Freudian
psychoanalysis
. The psychogenic view prevailed well into the 20th century.
was raised when an encephalitis epidemic
from 1918–1926 led to a subsequent epidemic of tic disorders. The psychoanalytic theory was so dominant that it was claimed that an organic component alone would not be sufficient to produce Tourette syndrome. At the time, psychiatrists believed patients with tics must also be suffering from unresolved psychological disturbances or psychosexual conflicts, and psychiatric intervention was the preferred method of treatment. Patients and their families were told that their own psychological maladjustments were to blame for their symptoms, adding to the burden carried by the patients and their families. Until the early 1970s, psychoanalysis was the preferred intervention for Tourette syndrome.
During the 1960s and 1970s, as the beneficial effects of haloperidol
(Haldol) on tics became known, the psychoanalytic approach to Tourette syndrome was questioned. The first description of haloperidol in the treatment of Tourette's was published by Seignot in 1961. The turning point came in 1965, when Arthur K. Shapiro
—described as "the father of modern tic disorder research"—treated a Tourette’s patient with haloperidol. Dr. Shapiro and his wife, Elaine Shapiro (PhD), reported the treatment in a 1968 article, and severely criticized the psychoanalytic approach.
The Shapiros, working with the patient families who founded the Tourette Syndrome Association
(TSA) in 1972, advanced the argument that Tourette's is a neurological, rather than psychological, disorder, and worked to persuade the media to promote information about Tourette's. The U.S. National Institutes of Health
(NIH) turned down a 1972 grant proposal from the TSA because "the reviewers believed there were probably no more than 100 cases of TS in the entire nation", and a 1973 registry reported only 485 cases worldwide. Subsequent articles on Tourette's in Good Housekeeping
, The New York Times
and Ann Landers produced an "enormous response, proving that there were many undiagnosed cases of TS across the United States".
Since the 1990s, a more neutral view of Tourette's has emerged, in which biological vulnerability and adverse environmental events are seen to interact. In 2000, the American Psychiatric Association
published the DSM-IV-TR, revising the text of DSM-IV to no longer require that symptoms of tic disorders cause distress or impair functioning. However, multiple studies published since 2000 have consistently demonstrated that the prevalence is much higher than previously thought. The emerging consensus is that 1–10 children per 1,000 have Tourette's, with several studies supporting a tighter range of 6–8 children per 1,000. Using year 2000 census data, a prevalence range of 1–10 per 1,000 yields an estimate of 53,000–530,000 school-age children with Tourette's in the US and a prevalence range of 6–10 per 1,000 means that 64,000–106,000 children aged 5–18 years may have Tourette's in the UK. Most of these children are undiagnosed and have mild symptoms without distress or impairment.
, neurophysiology
, and neuropathology
. The TSA
supports a clinical database that may help identify genes involved in Tourette syndrome, and the TSA International Genetic Consortium has collected a database on large extended families for future studies. Novel neuroimaging studies are being employed to study tic expression and functional or cognitive deficits in TS patients. Studies of Tourette's neurophysiology and neuropathology are attempting to link deficits in Tourette's to specific brain mechanisms, and have taken advantage of a brain bank sponsored by the TSA. Clinical trial
s have focused on understanding tic suppression, comorbid conditions, novel treatment approaches such as botulinum toxin
, and targeted behavioral therapies. Controversy remains in the areas of deep brain stimulation
and PANDAS.
Questions remain regarding how best to classify Tourette syndrome, and how closely Tourette's is related to other movement disorders or psychiatric disorders. Good epidemiologic data is still lacking, and available treatments are not risk free and not always well tolerated.
The direction of current and future research in Tourette's was outlined in a 2005 journal article 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 it should be studied, and how it should be (medically) treated.
According to Swerdlow, "the 'core' TS conundrum" is a lack of consensus about the definition of Tourette syndrome. 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 disorder
s. Individuals who have only tics may not be functionally impaired, raising the question of whether Tourette's as currently defined should be a DSM diagnosis. Swerdlow highlights the importance of studies in new areas such as behavioral techniques, and says that "the whole-cloth dismissal of psychologic forces in the pathobiology of TS was a strategic error". Questions remain about whether co-occurring (comorbid) 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 estimates of the prevalence of TS (the question of "who has it?"). Older estimates "came from tertiary referral samples, the sickest of the sick"; greater prevalence casts the condition in an entirely new light, and calls for new biological models of the condition and new approaches to addressing a more common disorder. Discovering the causes of Tourette's may help resolve the questions of what it is and who has it. The autosomal dominant inheritance model has not been validated, and past research has been affected by the problem of referred samples, which may not reflect broader populations of persons with Tourette's. Probabilistic genetic models may yield better clues than the "one gene equals one disorder" approach. One of the most controversial presumed causes, the PANDAS hypothesis, has sparked disagreement.
Expanding criteria for the diagnosis, and increasing awareness of the impact of comorbid diagnoses, has resulted in further questions of how to study Tourette's. Tourette's patients are often recruited from sources that introduce ascertainment bias towards one 'type' of TS. Developing and applying standardized instruments, along with a greater awareness of ascertainment bias in recruitment sources, will be important in genetic studies. We do not know if "we lose both signals and are just adding noise to the experimental outcome" when comorbid 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 heterogeneous condition, with waxing and waning symptoms. The inherently changing nature of its core symptoms complicates research design, resulting in questions about medications in clinical practice. Results from case studies may not be borne out by controlled or prospective, longitudinal studies, stimulant
s may be underused, 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
, and alternative therapies involving unstudied efficacy and side effects are pursued by many parents.
In the USA, the NIH has ongoing clinical trials, and the TSA funds ongoing research through its Research Program and Research Grant Awards. Other worldwide ongoing trials can be found by contacting Tourette syndrome advocacy groups.
Tourette syndrome
Tourette syndrome is an inherited neuropsychiatric disorder with onset in childhood, characterized by multiple physical tics and at least one vocal tic; these tics characteristically wax and wane...
is an inherited
Heredity
Heredity is the passing of traits to offspring . This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause some species to evolve...
neurological disorder with onset in childhood, characterized by the presence of multiple physical (motor) tic
Tic
A tic is a sudden, repetitive, nonrhythmic, stereotyped motor movement or vocalization involving discrete muscle groups. 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...
s and at least one vocal (phonic) tic.
The eponym
Eponym
An eponym is the name of a person or thing, whether real or fictitious, after which a particular place, tribe, era, discovery, or other item is named or thought to be named...
was bestowed by Jean-Martin Charcot
Jean-Martin Charcot
Jean-Martin Charcot was a French neurologist and professor of anatomical pathology. He is known as "the founder of modern neurology" and is "associated with at least 15 medical eponyms", including Charcot-Marie-Tooth disease and amyotrophic lateral sclerosis...
(1825–93) on behalf of his resident, Georges Albert Édouard Brutus Gilles de la Tourette
Georges Gilles de la Tourette
Georges Albert Édouard Brutus Gilles de la Tourette was a French neurologist who is the eponym of Tourette syndrome, a neurological condition...
(1859–1904), a French physician and neurologist
Neurology
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
, who published an account of nine patients with Tourette's in 1885. The possibility that movement disorder
Movement disorder
Movement disorders include:* Akathisia * Akinesia * Associated Movements * Athetosis...
s, including Tourette syndrome, might have an organic origin was raised when an encephalitis
Encephalitis
Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...
epidemic from 1918–1926 led to a subsequent epidemic of tic disorder
Tic disorder
Tic disorders are defined in the Diagnostic and Statistical Manual of Mental Disorders based on type and duration of tics...
s. Research in 1972 advanced the argument that Tourette's is a neurological, rather than psychological
Psychology
Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...
, disorder; since the 1990s, a more neutral view of Tourette's
Causes and origins of Tourette syndrome
Causes and origins of Tourette syndrome have not been fully elucidated. Tourette syndrome 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...
has emerged, in which biological vulnerability and adverse environmental events are seen to interact.
Findings since 1999 have advanced TS science in the areas of genetics, neuroimaging
Neuroimaging
Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain...
, neurophysiology
Neurophysiology
Neurophysiology is a part of physiology. Neurophysiology is the study of nervous system function...
, and neuropathology
Neuropathology
Neuropathology is the study of disease of nervous system tissue, usually in the form of either small surgical biopsies or whole autopsy brains. Neuropathology is a subspecialty of anatomic pathology, neurology, and neurosurgery...
. Questions remain regarding how best to classify Tourette syndrome, and how closely Tourette's is related to other movement disorders or psychiatric
Psychiatry
Psychiatry is the medical specialty devoted to the study and treatment of mental disorders. These mental disorders include various affective, behavioural, cognitive and perceptual abnormalities...
disorders. Good epidemiologic data is still lacking, and available treatments
Treatment of Tourette syndrome
Tourette syndrome is an inherited neuropsychiatric disorder with onset in childhood, characterized by the presence of motor and phonic tics...
are not risk free and not always well tolerated.
Nineteenth century
The first presentation of Tourette syndrome is thought to be in a 1489 book, Malleus maleficarum ("Witch's hammer") by Jakob Sprenger and Heinrich Kraemer, describing a priest whose tics were "believed to be related to possession by the devil". A French doctor, Jean Marc Gaspard ItardJean Marc Gaspard Itard
Jean Marc Gaspard Itard was a French physician born in Provence.Without a university education and working at a bank, he was forced to enter the army during the French Revolution but presented himself as a physician at that time...
, reported the first case of Tourette syndrome in 1825, describing Marquise de Dampierre, an important woman of nobility in her time, whose episodes later understood to be coprolalia
Coprolalia
Coprolalia is involuntary swearing or the involuntary utterance of obscene words or socially inappropriate and derogatory remarks. Coprolalia comes from the Greek κόπρος meaning "feces" and λαλιά from lalein, "to talk"...
"were obviously in stark contrast to the lady's background, intellect, and refined manners".
Jean-Martin Charcot, an influential French physician, assigned his resident Georges Albert Édouard Brutus Gilles de la Tourette, a French physician and neurologist, to study patients at the Salpêtrière
Pitié-Salpêtrière Hospital
The Pitié-Salpêtrière Hospital is a teaching hospital located in Paris, France. Part of the Assistance publique - Hôpitaux de Paris, it is one of Europe's largest hospitals...
Hospital, with the goal of defining an illness distinct from hysteria
Hysteria
Hysteria, in its colloquial use, describes unmanageable emotional excesses. People who are "hysterical" often lose self-control due to an overwhelming fear that may be caused by multiple events in one's past that involved some sort of severe conflict; the fear can be centered on a body part, or,...
and from chorea. Charcot and Tourette believed that the "tic illness" they had observed was an untreatable, chronic, and progressive hereditary condition. History is unclear on whether Charcot had examined the Marquise de Dampierre, but his publications mention having met her socially and overhearing her most common utterances of "merde and foutu cochon (which translates literally as filthy pig but the truer colloquial meaning is 'fucking pig')".
In 1885, Gilles de la Tourette published an account of nine patients, Study of a Nervous Affliction, concluding that a new clinical category should be defined. His description included accounts of Marquise de Dampierre, previously described by Itard, as a reclusive aristocratic lady who "ticked and blasphemed" from the age of seven until her death at the age of 80 years. Gilles de la Tourette describes the common feature of involuntary movements or tics in all nine patients. The eponym was later bestowed by Charcot after and on behalf of Gilles de la Tourette.
Little progress was made over the next century in explaining or treating tics. With limited clinical experience, involving typically one or two patients, authors advanced different ideas, including brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s similar to those resulting from rheumatic chorea
Sydenham's chorea
Sydenham's chorea or chorea minor is a disease characterized by rapid, uncoordinated jerking movements affecting primarily the face, feet and hands. Sydenham's chorea results from childhood infection with Group A beta-hemolytic Streptococci and is reported to occur in 20-30% of patients with...
or encephalitis lethargica
Encephalitis lethargica
Encephalitis lethargica or von Economo disease is an atypical form of encephalitis. Also known as "sleepy sickness" , it was first described by the neurologist Constantin von Economo in 1917. The disease attacks the brain, leaving some victims in a statue-like condition, speechless and motionless...
as a cause of tics, faulty mechanisms of normal habit
Habituation
Habituation can be defined as a process or as a procedure. As a process it is defined as a decrease in an elicited behavior resulting from the repeated presentation of an eliciting stimulus...
formation, and treatment with Freudian
Sigmund Freud
Sigmund Freud , born Sigismund Schlomo Freud , was an Austrian neurologist who founded the discipline of psychoanalysis...
psychoanalysis
Psychoanalysis
Psychoanalysis is a psychological theory developed in the late 19th and early 20th centuries by Austrian neurologist Sigmund Freud. Psychoanalysis has expanded, been criticized and developed in different directions, mostly by some of Freud's former students, such as Alfred Adler and Carl Gustav...
. The psychogenic view prevailed well into the 20th century.
Twentieth century
The possibility that movement disorders, including Tourette syndrome, might have an organic originOrganic disease
An organic disease is one which involves or affects physiology or bodily organs. A disease in which there is a physiological change to some tissue or organ of the body....
was raised when an encephalitis epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
from 1918–1926 led to a subsequent epidemic of tic disorders. The psychoanalytic theory was so dominant that it was claimed that an organic component alone would not be sufficient to produce Tourette syndrome. At the time, psychiatrists believed patients with tics must also be suffering from unresolved psychological disturbances or psychosexual conflicts, and psychiatric intervention was the preferred method of treatment. Patients and their families were told that their own psychological maladjustments were to blame for their symptoms, adding to the burden carried by the patients and their families. Until the early 1970s, psychoanalysis was the preferred intervention for Tourette syndrome.
During the 1960s and 1970s, as the beneficial effects of haloperidol
Haloperidol
Haloperidol is a typical antipsychotic. It is in the butyrophenone class of antipsychotic medications and has pharmacological effects similar to the phenothiazines....
(Haldol) on tics became known, the psychoanalytic approach to Tourette syndrome was questioned. The first description of haloperidol in the treatment of Tourette's was published by Seignot in 1961. The turning point came in 1965, when Arthur K. Shapiro
Arthur K. Shapiro
Arthur K. Shapiro was a psychiatrist and expert on Tourette syndrome. His "contributions to the understanding of Tourette syndrome completely changed the prevailing view of this disorder"; he has been described as "the father of modern tic disorder research" and is "revered by his colleagues as...
—described as "the father of modern tic disorder research"—treated a Tourette’s patient with haloperidol. Dr. Shapiro and his wife, Elaine Shapiro (PhD), reported the treatment in a 1968 article, and severely criticized the psychoanalytic approach.
The Shapiros, working with the patient families who founded the Tourette Syndrome Association
Tourette Syndrome Association
The Tourette Syndrome Association , based in Bayside, New York, United States, is a non-profit voluntary organization and the only national health-related organization serving people with Tourette syndrome. It was founded in 1972 by five couples, parents of children with Tourette syndrome...
(TSA) in 1972, advanced the argument that Tourette's is a neurological, rather than psychological, disorder, and worked to persuade the media to promote information about Tourette's. The U.S. National Institutes of Health
National Institutes of Health
The National Institutes of Health are an agency of the United States Department of Health and Human Services and are the primary agency of the United States government responsible for biomedical and health-related research. Its science and engineering counterpart is the National Science Foundation...
(NIH) turned down a 1972 grant proposal from the TSA because "the reviewers believed there were probably no more than 100 cases of TS in the entire nation", and a 1973 registry reported only 485 cases worldwide. Subsequent articles on Tourette's in Good Housekeeping
Good Housekeeping
Good Housekeeping is a women's magazine owned by the Hearst Corporation, featuring articles about women's interests, product testing by The Good Housekeeping Institute, recipes, diet, health as well as literary articles. It is well known for the "Good Housekeeping Seal," popularly known as the...
, The New York Times
The New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...
and Ann Landers produced an "enormous response, proving that there were many undiagnosed cases of TS across the United States".
Since the 1990s, a more neutral view of Tourette's has emerged, in which biological vulnerability and adverse environmental events are seen to interact. In 2000, the American Psychiatric Association
American Psychiatric Association
The American Psychiatric Association is the main professional organization of psychiatrists and trainee psychiatrists in the United States, and the most influential worldwide. Its some 38,000 members are mainly American but some are international...
published the DSM-IV-TR, revising the text of DSM-IV to no longer require that symptoms of tic disorders cause distress or impair functioning. However, multiple studies published since 2000 have consistently demonstrated that the prevalence is much higher than previously thought. The emerging consensus is that 1–10 children per 1,000 have Tourette's, with several studies supporting a tighter range of 6–8 children per 1,000. Using year 2000 census data, a prevalence range of 1–10 per 1,000 yields an estimate of 53,000–530,000 school-age children with Tourette's in the US and a prevalence range of 6–10 per 1,000 means that 64,000–106,000 children aged 5–18 years may have Tourette's in the UK. Most of these children are undiagnosed and have mild symptoms without distress or impairment.
Contemporary
As of 2006, the Tourette Syndrome Association has contacts in more than 50 countries. The Tourette syndrome International database Consortium (TIC) brought together data on clinical samples of patients with Tourette syndrome from twenty-two countries (Argentina, Australia, Austria, Belgium, Brazil, Canada, Denmark, Germany, Hungary, Iceland, Israel, Italy, Japan, The Netherlands, Norway, Peoples Republic of China, Poland, South Africa, Sweden, Turkey, the US and the UK); Tourette's has also been studied in Chile, Colombia, Costa Rica, India, Indonesia, Korea, and Spain.Research directions and controversies
Findings reported in published studies of Tourette syndrome since 1999 have advanced TS science in the areas of genetics, neuroimagingNeuroimaging
Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain...
, neurophysiology
Neurophysiology
Neurophysiology is a part of physiology. Neurophysiology is the study of nervous system function...
, and neuropathology
Neuropathology
Neuropathology is the study of disease of nervous system tissue, usually in the form of either small surgical biopsies or whole autopsy brains. Neuropathology is a subspecialty of anatomic pathology, neurology, and neurosurgery...
. The TSA
Tourette Syndrome Association
The Tourette Syndrome Association , based in Bayside, New York, United States, is a non-profit voluntary organization and the only national health-related organization serving people with Tourette syndrome. It was founded in 1972 by five couples, parents of children with Tourette syndrome...
supports a clinical database that may help identify genes involved in Tourette syndrome, and the TSA International Genetic Consortium has collected a database on large extended families for future studies. Novel neuroimaging studies are being employed to study tic expression and functional or cognitive deficits in TS patients. Studies of Tourette's neurophysiology and neuropathology are attempting to link deficits in Tourette's to specific brain mechanisms, and have taken advantage of a brain bank sponsored by the TSA. Clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
s have focused on understanding tic suppression, comorbid conditions, novel treatment approaches such as botulinum toxin
Botulinum toxin
Botulinum toxin is a protein produced by the bacterium Clostridium botulinum, and is considered the most powerful neurotoxin ever discovered. Botulinum toxin causes Botulism poisoning, a serious and life-threatening illness in humans and animals...
, and targeted behavioral therapies. Controversy remains in the areas of deep brain stimulation
Deep brain stimulation
Deep brain stimulation is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain...
and PANDAS.
Questions remain regarding how best to classify Tourette syndrome, and how closely Tourette's is related to other movement disorders or psychiatric disorders. Good epidemiologic data is still lacking, and available treatments are not risk free and not always well tolerated.
The direction of current and future research in Tourette's was outlined in a 2005 journal article 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 it should be studied, and how it should be (medically) treated.
According to Swerdlow, "the 'core' TS conundrum" is a lack of consensus about the definition of Tourette syndrome. 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 disorder
Tic disorder
Tic disorders are defined in the Diagnostic and Statistical Manual of Mental Disorders based on type and duration of tics...
s. Individuals who have only tics may not be functionally impaired, raising the question of whether Tourette's as currently defined should be a DSM diagnosis. Swerdlow highlights the importance of studies in new areas such as behavioral techniques, and says that "the whole-cloth dismissal of psychologic forces in the pathobiology of TS was a strategic error". Questions remain about whether co-occurring (comorbid) conditions should be part of the core definition, and why sensory phenomena
Sensory phenomena
Sensory phenomena are general feelings, urges or bodily sensations that precede or accompany repetitive behaviors associated with Tourette syndrome and tic disorders...
, 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 estimates of the prevalence of TS (the question of "who has it?"). Older estimates "came from tertiary referral samples, the sickest of the sick"; greater prevalence casts the condition in an entirely new light, and calls for new biological models of the condition and new approaches to addressing a more common disorder. Discovering the causes of Tourette's may help resolve the questions of what it is and who has it. The autosomal dominant inheritance model has not been validated, and past research has been affected by the problem of referred samples, which may not reflect broader populations of persons with Tourette's. Probabilistic genetic models may yield better clues than the "one gene equals one disorder" approach. One of the most controversial presumed causes, the PANDAS hypothesis, has sparked disagreement.
Expanding criteria for the diagnosis, and increasing awareness of the impact of comorbid diagnoses, has resulted in further questions of how to study Tourette's. Tourette's patients are often recruited from sources that introduce ascertainment bias towards one 'type' of TS. Developing and applying standardized instruments, along with a greater awareness of ascertainment bias in recruitment sources, will be important in genetic studies. We do not know if "we lose both signals and are just adding noise to the experimental outcome" when comorbid 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 heterogeneous condition, with waxing and waning symptoms. The inherently changing nature of its core symptoms complicates research design, resulting in questions about medications in clinical practice. Results from case studies may not be borne out by controlled or prospective, longitudinal studies, stimulant
Stimulant
Stimulants are psychoactive drugs which induce temporary improvements in either mental or physical function or both. Examples of these kinds of effects may include enhanced alertness, wakefulness, and locomotion, among others...
s may be underused, 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
Deep brain stimulation
Deep brain stimulation is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain...
, and alternative therapies involving unstudied efficacy and side effects are pursued by many parents.
In the USA, the NIH has ongoing clinical trials, and the TSA funds ongoing research through its Research Program and Research Grant Awards. Other worldwide ongoing trials can be found by contacting Tourette syndrome advocacy groups.