Tourette syndrome (TS), also known as Tourette’s Disorder, is a neurodevelopmental disorder characterized by multiple motor tics and at least one vocal tic present for greater than one year. Among the neurodevelopmental disorders in the DSM-5, TS is the most complex of the spectrum of tic disorders, which includes:
- Tourette’s disorder
- Persistent motor or vocal tic disorder: one or more motor or vocal tics have been present for greater than one year
- Provisional tic disorder: motor and/or vocal tics have been present for less than a year.
Psychiatric disorders, such as obsessive-compulsive disorder (OCD) and attention-deficit hyperactivity disorder (ADHD) frequently co-occur in TS. Tic symptoms typically begin in early childhood, peak before puberty, and attenuate later in adolescence.
Symptoms and phenomenology
Tics are rapid, repetitive, non-rhythmic movements or vocalizations. Motor and vocal tics are divided into two classes: simple and complex. Simple motor tics are brief movements involving one muscle group. Simple vocal tics are characterized by simple sounds.
- Simple motor tics include eye blinks, facial grimaces, head and neck jerks, and shoulder shrugs. Briefly sustained postures (e.g., blepharospasm, oculogyric movements, and sustained mouth opening) can also be classified as simple motor tics.
- Simple vocal tics include coughing, sniffing, throat clearing, grunting, and squeaking.
Complex motor tics are more purposeful or orchestrated patterns of movement; complex vocal tics are longer, more orchestrated patterns of speech.
- Examples of complex motor tics are turning while walking, echopraxia (imitating gestures) and copropraxia (obscene gestures).
- Complex vocal tics include repeated words or phrases, echolalia (repeating another person's words or phrases) and coprolalia (uttering obscenities). Although coprolalia can cause considerable social distress, it is infrequent, and occurs in only approximately 10% of patients.
A distinguishing characteristic of tics are the sensations that may precede the movement or sound, termed premonitory sensations or "urges." Sometimes patients can localize these feelings to particular parts of the body from which the tic emerged.
Even if not localizable, patients often describe a feeling of inner discomfort, using words such as a “build up of tension," or describe an unexplainable urge or impulse to perform the tic. Most patients experience an intensification of these sensations or urges when they suppress their tics.
Patients also often describe a strong need to repeat the tic until it feels "just right". After performing the tic, a sense of relief is experienced, although sometimes brief.
Descriptions of these sensations may be difficult for younger patients to express, but there is a quantitative, pictorial rating scale of these urges that can be used with children.
Epidemiology
TS is reported worldwide, with prevalence from 0.3% to 0.9%. It affects boys 3 to 4 times more frequently than girls.The vast majority of individuals with TS have behavioral and/or emotional symptoms or disorders; only 12% across all ages are reported to have only tics without other associated conditions.
From a worldwide dataset, ADHD is the most common comorbid psychiatric disorder, and accounts for about 55% of the behavioral findings. Other disorders, such as mood and anxiety disorders and learning disorders, are also frequently present.
Etiology
The cause of TS remains unknown, although evidence from genetic studies suggests that TS is inherited. Genetic factors seem to be the most important etiology, given significant familial aggregation and supporting twin studies.
Monozygotic twin studies show 53% concordance for TS and 77% for persistent (chronic) motor tics, whereas dizygotic twins show 8% and 23% concordance, respectively.
Environmental factors, including perinatal insults, sex-hormone exposure during brain development, and psychosocial stressors, are also thought to contribute, and thus the overall expression of TS is thought to be multifactorial.
Diagnosis
Diagnosis is made by a comprehensive clinical history from reliable sources, most often parents. Currently there is no identifiable biological marker for a TS diagnosis. A thorough, detailed history focusing on onset, time course, phenomenology such as urges or sensations, exacerbating and ameliorating factors, family history, and comorbid symptoms is essential. A general medical and neurological exam is indicated.
When eliciting history from the parent and patient, inquiry regarding onset of tics is important, as they typically begin in early childhood, followed by a waxing and waning course. Often tics worsen in late childhood prior to puberty.
Although tics tend to wax and wane, with one tic replacing another, sometimes tics can present abruptly or in acute bursts. Explosive, acute onset over 24 to 48 hours, particularly of OCD symptoms, may be suggestive of infectious or autoimmune etiology.
Potential day-to-day exacerbating factors, such as medications (stimulants in some patients, including caffeine and over-the-counter decongestants or cold remedies), fatigue, boredom, and stressors should be noted.
Tic symptoms may be difficult to disentangle from other common childhood symptoms of allergies or cough-variant asthma. Inquiry regarding seasonal patterns, and presence of other allergy-associated symptoms such as rhinitis and post-nasal drip, can be helpful in the differential diagnostic process.
Additionally, at times it may be difficult to differentiate complex motor tics from compulsions, as OCD symptoms frequently co-occur in children with TS. Repetitive behaviors preceded by urges or sensations are more likely to be complex tics, whereas repetitive behaviors that are preceded by a cognition, often a worry, are more likely to be compulsions.
Source: http://www.news-medical.net/health/Definition-and-DSM-5-Classification-Tic-Disorders.aspx
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