Tic Disorders

Tic disorders are distinguished by the type of tic symptoms, their frequency, and the pattern in which they emerge over time. Tics are abnormal movements or vocalizations that most commonly affect the muscles of the face and neck, such as eye-blinking, head-jerking, mouth-grimacing, or head-shaking. Typical vocal tics include throat-clearing, grunting, snorting, and coughing. Tics are defined as rapid and repetitive muscle contractions resulting in movements or vocalizations that are experienced as involuntary. Children and adolescents may exhibit tic behaviors that occur after a stimulus or in response to an internal urge. Tic disorders comprise a group of neuropsychiatric disorders that generally begin in childhood or adolescence; they have a stable or fluctuating course in childhood and generally wane by adolescence. Although tics are not volitional, in some individuals they may be suppressed for periods.

TOURETTE’S DISORDER

According to the text revision of the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), tics in Tourette’s disorder are multiple motor tics and one or more vocal tics. The tics occur many times a day for more than 1 year. Tourette’s disorder causes distress or significant impairment in important areas of functioning. The disorder has an onset before the age of 18 years, and it is not caused by a substance or by a general medical condition.

Georges Gilles de la Tourette (1857-1904) first described a patient with what was later known as Tourette’s disorder in 1885, while he was studying with Jean-Martin Charcot in France. De la Tourette noted a syndrome in several patients that included multiple motor tics, coprolalia, and echolalia.

Epidemiology

The lifetime prevalence of Tourette’s disorder is estimated to be 4 to 5 per 10,000. More children exhibit this disorder than adults, such that 5 to 30 of 10,000 children are affected, but by adulthood, only 1 to 2 of 10,000 meet diagnostic criteria. The onset of the motor component of the disorder generally occurs by the age of 7 years; vocal tics emerge on average by the age of 11 years. Tourette’s disorder occurs about three times more often in boys than in girls.

Etiology

Genetic Factors.

Twin studies, adoption studies, and segregation analysis studies all support a genetic cause for Tourette’s disorder. Twin studies indicate that concordance for the disorder in monozygotic twins is significantly greater than that in dizygotic twins. That Tourette’s disorder and chronic motor or vocal tic disorder are likely to occur in the same families lends support to the view that the disorders are part of a genetically determined spectrum. The sons of mothers with Tourette’s disorder seem to be at the highest risk for the disorder. Evidence in some families indicates that Tourette’s disorder is transmitted in an autosomal dominant fashion. Recent studies of a long family pedigree suggest that Tourette’s disorder may be transmitted in a bilinear mode; that is, Tourette’s disorder appears to be inherited through an autosomal pattern in some families, intermediate between dominant and recessive. A recent study of 174 unrelated probands with Tourette’s disorder identified a greater-than-chance occurrence of a rare sequence variant in SLITRK1 believed to be a candidate gene on chromosome 13q31.

A relation is found between Tourette’s disorder and attention-deficit/hyperactivity disorder (ADHD); up to half of all patients with Tourette’s disorder also have ADHD. A relation also appears between Tourette’s disorder and obsessive-compulsive disorder (OCD); up to 40 percent of all individuals with Tourette’s disorder also have OCD. In addition, first-degree relatives of persons with Tourette’s disorder are at high risk for the development of the disorder, of chronic motor or vocal tic disorder, and of OCD. The presence of symptoms of ADHD in more than half of persons with Tourette’s disorder raises questions about a genetic relation between these two disorders.

Neurochemical and Neuroanatomical Factors.

Compelling, but indirect, evidence of dopamine system involvement in tic disorders includes the observations that pharmacological agents that antagonize dopamine (haloperidol [Haldol], pimozide [Orap], and fluphenazine [Prolixin]) suppress tics and that agents that increase central dopaminergic activity (methylphenidate [Ritalin], amphetamines, pemoline [Cylert], and cocaine) tend to exacerbate tics. The relation of tics to neurotransmitter systems is complex and not well understood; for example, in some cases, antipsychotic medications, such as haloperidol, are not effective in reducing tics, and the effect of stimulants on tic disorders reportedly varies. In some cases, Tourette’s disorder has emerged during treatment with antipsychotic medications.

More direct analyses of the neurochemistry of Tourette’s disorder have been possible using brain proton magnetic resonance spectroscopy, a method only recently used to investigate this disorder. A recent investigation examining the cellular neurochemistry of patients with Tourette’s disorder using magnetic resonance spectroscopy of the frontal cortex, caudate nucleus, putamen, and thalamus demonstrated that these patients had a reduced amount of choline and N-acetylaspartate in the left putamen along with reduced levels of bilaterally in the putamen. In the frontal cortex, patients with Tourette’s disorder were found to have lower concentrations of N-acetylaspartate bilaterally, lower levels of creatine on the right side, and reduced myoinositol on the left side. These results imply that deficits in the density of neuronal and nonneuronal cells are present in patients with Tourette’s disorder.

Endogenous opioids may be involved in tic disorders and OCD. Some evidence indicates that pharmacological agents that antagonize
endogenous opiates—for example, naltrexone (ReVia)—reduce tics and attention deficits in patients with Tourette’s disorder. Abnormalities in the noradrenergic system have been implicated in some cases by the reduction of tics with clonidine (Catapres). This adrenergic agonist reduces the release of norepinephrine in the central nervous system and, thus, may reduce activity in the dopaminergic system. Abnormalities in the basal ganglia result in various movement disorders, such as Huntington’s disease, and are implicated as possible sites of disturbance in Tourette’s disorder, OCD, and ADHD.

Immunological Factors and Postinfection.

An autoimmune process that is secondary to streptococcal infections is a potential mechanism for Tourette’s disorder. Such a process could act synergistically with a genetic vulnerability for this disorder. Poststreptococcal syndromes have also been associated with one potential causative factor in the development of OCD in children.

Diagnosis and Clinical Features

To make a diagnosis of Tourette’s disorder, clinicians must obtain a history of multiple motor tics and the emergence of at least one vocal tic at some point in the disorder. According to DSM-IV-TR, the tics must occur many times a day nearly every day or intermittently for more than 1 year. The average age of onset of tics is 7 years, but tics can occur as early as age 2 years. The onset must occur before the age of 18 years (Table 42-1).

In Tourette’s disorder, the initial tics are in the face and neck. Over time, the tics tend to occur in a downward progression. The most commonly described tics are those affecting the face and head, the arms and hands, the body and lower extremities, and the respiratory and alimentary systems. In these areas, the tics take the form of grimacing; forehead puckering; eyebrow-raising; eyelid-blinking; winking; nose-wrinkling; nostril-trembling; mouth-twitching; displaying the teeth; biting the lips and other parts; tongue-extruding; protracting the lower jaw; nodding, jerking, or shaking the head; twisting the neck; looking sideways; head-rolling; hand-jerking; arm-jerking; plucking fingers; writhing fingers; fist-clenching; shoulder-shrugging; foot, knee, or toe shaking; walking peculiarly; body writhing; jumping; hiccupping; sighing; yawning; snuffing; blowing through the nostrils; whistling; belching; sucking or smacking sounds; and clearing the throat. Several assessment instruments are available that are useful in making diagnoses of tic disorders, including comprehensive self-report assessment tools, such as the Tic Symptom Self Report and the Yale Global Tic Severity Scale, administered by a clinician.

Table 42-1 DSM-IV-TR Diagnostic Criteria for Tourette’s Disorder

A.	Both multiple motor and one or more vocal tics have been present at some time during the illness, although not necessarily concurrently. (A tic is a sudden, rapid, recurrent, nonrhythmic, stereotyped motor movement or vocalization.)
B.	The tics occur many times a day (usually in bouts) nearly every day or intermittently throughout a period of more than 1 year, and during this period there was never a tic-free period of more than 3 consecutive months.
C.	The onset is before age 18 years.
D.	The disturbance is not due to the direct physiological effects of a substance (e.g., stimulants) or a general medical condition (e.g., Huntington’s disease or postviral encephalitis).
From American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Text rev. Washington, DC: American Psychiatric Association; copyright 2000, with permission.

Typically, prodromal behavioral symptoms (e.g., irritability, attention difficulties, and poor frustration tolerance) are evident before, or coincide with, the onset of tics. More than 25 percent of persons in some studies received stimulants for a diagnosis of ADHD before receiving a diagnosis of Tourette’s disorder. The most frequent initial symptom is an eye-blink tic, followed by a head tic or a facial grimace. Most complex motor and vocal symptoms emerge several years after the initial symptoms. Coprolalia usually begins in early adolescence and occurs in about one third of all patients. Mental coprolalia—in which a patient thinks a sudden, intrusive, socially unacceptable thought or obscene word—can also occur. In some severe cases, physical injuries, including retinal detachment and orthopedic problems, have resulted from severe tics.

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