Tic disorders
Tic Disorders
Four disorders are included in this section: Tourette's Disorder, Chronic Motor or Vocal Tic Disorder, Transient Tic Disorder, and Tic Disorder Not Otherwise Specified. A tic is a sudden, rapid, recurrent, nonrhythmic, stereotyped motor movement or vocalization. Motor and vocal tics may be simple (involving only a few muscles or simple sounds) or complex (involving multiple groups of muscles recruited in orchestrated bouts or words and sentences). Examples of simple motor tics are eye blinking, nose wrinkling, neck jerking, shoulder shrugging, facial grimacing, and abdominal tensing. These tics usually last less than several hundred milliseconds. Complex motor tics include hand gestures, jumping, touching, pressing, stomping, facial contortions, repeatedly smelling an object, squatting, deep knee bends, retracing steps, twirling when walking, and assuming and holding unusual postures (including "dystonic tics" such as holding the neck in a particular tensed position). These tics are longer in duration, lasting seconds or longer. Copropraxia (a sudden, tic-like vulgar, sexual, or obscene gesture) and mirror phenomena such as echopraxia (involuntary, spontaneous imitation of someone else's movements) are complex motor tics.
Simple vocal tics are meaningless sounds such as throat clearing, grunting, sniffing, snorting, and chirping. Complex vocal ticsmore clearly involve speech and language and include the sudden, spontaneous expression of single words or phrases; speech blocking; sudden and meaningless changes in the pitch, emphasis, or volume of speech; palilalia (repeating one's own sounds or words); and echolalia (repeating the last-heard sound, word, or phrase). Coprolalia is the sudden, inappropriate expression of a socially unacceptable word or phrase and may include obscenities as well as specific ethnic, racial, or religious slurs. Coprolalia is found in fewer than 10% of individuals with a tic disorder.
Tics generally are experienced as irresistible but can be suppressed for varying lengths of time. Some children (and an occasional adult) are not aware of their tics. However, with development, many (but not all) persons with tics experience a premonitory urge-a rising tension or somatic sensation in a part of the body that precedes the motor or vocal tic, and a feeling of relief or tension reduction following the expression of the tic. Individuals with tics may feel that the tic is between "voluntary" and "involuntary" in that it is often experienced as a giving in to a mounting tension or bodily need, similar to the tension that precedes a sneeze or the almost irresistible need to scratch an itch. An individual may feel the need to perform a complex tic in a specific way or repeatedly until he or she achieves the feeling that the tic has been done "just right." Only then will the individual experience a reduction in the anxiety or tension.
Tics are often emitted in bouts of one or several tics; the bouts are separated by periods of non-tic behavior lasting from seconds to hours. Tics generally change in severity (frequency of tics, forcefulness, and the degree tics disrupt ongoing behavior) during the course of hours and over the course of a day. Tics may vary in frequency and disruptiveness in different contexts. For example, children and adults may be better able to suppress tics when in school, at work, or in the physician's office than at home. Tics generally decrease or stop during sleep, although some individuals have occasional tics while asleep or awaken suddenly with a tic. Tics are often more frequent when a person relaxes in private (e.g., when watching television) and are decreased when the individual engages in directed, effortful activity (e.g., reading or sewing). Tics may be exacerbated during periods of stress, such as when there are heightened work pressures or during examinations.
Differential Diagnosis
Tic Disorders must be distinguished from other types of abnormal movements that may accompany general medical conditions (e.g., Huntington's disease, stroke, Lesch-Nyhan syndrome, Wilson's disease, Sydenham's chorea, multiple sclerosis, postviral encephalitis, head injury) and from abnormal movements that are due to the direct effects of a substance (e.g., a neuroleptic medication). Taking account of the medical and family history, movement morphology, rhythm, and modifying influences can assist in making a correct diagnosis. Chorea typically is a simple, random, irregular, and nonstereotyped movement that has no premonitory component and increases when the person is distracted. Dystonic movements are slow, protracted twisting movements interspersed with prolonged states of muscular tension. Athetoid movements are slow, irregular, writhing movements, most frequently in the fingers and toes but often involving the neck. Myoclonic movements are brief, simple, shocklike muscle contractions that may affect parts of muscles or muscle groups. Unlike tics, myoclonic movements may continue during sleep. Hemiballismic movements are intermittent, coarse, large-amplitude, unilateral movements of the limbs. Spasms are stereotypic, prolonged movements involving the same groups of muscles that are usually slower but are sometimes more rapid than tics. Hemifacial spasm consists of irregular, repetitive, unilateral jerks of facial muscles. Synkinesis is an involuntary movement that is concurrent exclusively with a specific voluntary act (e.g., movement of the corner of the mouth when the person intends to close the eye).
When the tics are a direct physiological consequence of medication use, a Medication-Induced Movement Disorder Not Otherwise Specified would be diagnosed instead of a Tic Disorder (e.g., in the clearest case, when the tics occur with the use of a medication and stop when the medication is discontinued). In some cases, certain medications (e.g., stimulants) may exacerbate a preexisting Tic Disorder, in which case no additional diagnosis of a medication-induced disorder is necessary.
Tics must also be distinguished from Stereotypic Movement Disorder and stereotypies in Pervasive Developmental Disorders. Differentiating simple tics (e.g., eye blinking) from the complex movements characteristic of stereotyped movements is relatively straightforward. The distinction between complex motor tics and stereotyped movements is less clear-cut. In general, stereotyped movements appear to be more driven, rhythmic, self-stimulating or soothing, and intentional, whereas tics have a more involuntary quality (although some individuals describe tics as having a voluntary component) and generally occur in temporal bouts or clusters. Complex tics may be difficult to distinguish from compulsions (as in Obsessive-Compulsive Disorder); making this distinction is all the more challenging because Obsessive-Compulsive Disorder is common in individuals with Tic Disorders. Compulsions are performed in response to an obsession (e.g., hand washing to allay a concern about germs) or according to rules that must be applied rigidly (e.g., the need to line things up in a specific order). Compulsions typically are more elaborate than tics and are more likely to resemble "normal" behavior. Whereas compulsions are often, though not always, preceded by a persistent worry or concern, tics are more likely to be preceded by a transient "physical" tension in a part of the body (e.g., in the nose or shoulder muscles or in the throat) that is reduced by the tic. When individuals manifest symptoms of both Obsessive-Compulsive Disorder and a Tic Disorder (especially Tourette's Disorder), both diagnoses may be warranted. Certain vocal or motor tics (e.g., barking, echolalia, palilalia) must be distinguished from disorganized or catatonic behavior in Schizophrenia.
The Tic Disorders can be distinguished from one another based on duration and variety of tics and age at onset. Transient Tic Disorder includes motor and/or vocal tics lasting for at least 4 weeks but for no longer than 12 consecutive months. Tourette's Disorder and Chronic Motor or Vocal Tic Disorder each have a duration of more than 12 months, but Tourette's Disorder requires multiple motor tics and at least one vocal tic during part of this time. Often, the diagnosis may change over time during the natural history of a Tic Disorder. For example, during the first months, a child may be diagnosed as having a Transient Tic Disorder. After a year, with further tics and longer duration, the diagnosis may become Tourette's Disorder. Tic Disorder Not Otherwise Specified would be appropriate for clinically significant presentations lasting less than 4 weeks, for presentations with an age at onset above age 18 years, and for the unusual case of an individual with only one motor tic and only one vocal tic.