A tic is a sudden, repetitive, stereotyped, nonrhythmic movement (motor tic) or sound (phonic tic) that involves discrete groups of muscles. Tics can be invisible to the observer (e.g.; abdominal tensing or toe crunching). Movements of other movement disorders (e.g.; chorea, dystonia, myoclonus) must be distinguished from tics. Other conditions (e.g.; autism, stereotypic movement disorder) also include movements which may be confused with tics. Tics must also be distinguished from compulsions of OCD and seizure activity.
Description and classification
Tics are classified as motor vs. phonic, and simple vs. complex.
Motor tics are movement-based tics affecting discrete muscle groups.
Phonic tics are involuntary sounds produced by moving air through the nose, mouth, or throat. They may be alternately referred to as verbal tics or vocal tics, but most diagnosticians prefer the term phonic tics to reflect the notion that the vocal cords are not involved in all tics that produce sound.
Tics may increase as a result of stress, tiredness, or high energy emotions, which can include negative emotions, such as anxiety, but positive emotions as well, such as excitement or anticipation. Relaxation may result in a tic decrease or a tic increase (for instance, watching television or using a computer), while concentration in an absorbing activity often leads to a decrease in tics. Neurologist and writer Oliver Sacks describes a physician with severe Tourette syndrome, (Canadian Mort Doran, M.D., a pilot and surgeon in real life, although a pseudonym was used in the book), whose tics remit almost completely while he is performing surgery.
Immediately preceding tic onset, most individuals are aware of an urge that is similar to the need to yawn, sneeze, blink, or scratch an itch. Individuals describe the need to tic as a buildup of tension which they consciously choose to release, as if they "had to do it". 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.
Tics are described as semi-voluntary or "unvoluntary", because they are not strictly involuntary—they may be experienced as a voluntary response to the unwanted, premonitory urge. A unique aspect of tics, relative to other movement disorders, is that they are suppressible yet irresistible; they are experienced as an irresistible urge that must eventually be expressed. Some people with tics 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.
Simple motor tics are typically sudden, brief, meaningless movements, such as eye blinking or shoulder shrugging. Motor tics can be of an endless variety and may include such movements as hand-clapping, neck stretching, mouth movements, head, arm or leg jerks, and facial grimacing.
A simple phonic tic can be almost any possible sound or noise, with common vocal tics being throat clearing, coughing, sniffing, or grunting.
Complex motor tics are typically more purposeful-appearing and of a longer nature. Examples of complex motor tics are pulling at clothes, touching people, touching objects, echopraxia and copropraxia.
Complex phonic tics may fall into various categories, including echolalia (repeating words just spoken by someone else), palilalia (repeating one's own previously spoken words), lexilalia (repeating words after reading them) and coprolalia (the spontaneous utterance of socially-objectionable or taboo words or phrases). Coprolalia is a highly-publicized symptom of Tourette syndrome; however, according to the Tourette Syndrome Association, Inc. (TSA), fewer than 15% of TS patients exhibit coprolalia.
Tic disorders occur along a spectrum, ranging from mild to more severe, and are classified according to duration and severity (transient tics, chronic tics, or Tourette syndrome). Tourette syndrome is the more severe expression of a spectrum of tic disorders, which are thought to be due to the same genetic vulnerability. Nevertheless, most cases of Tourette syndrome are not severe. The treatment for the spectrum of tic disorders is similar to the treatment of Tourette syndrome.
Controversy and confusion
There is some confusion in media portrayals of tics. For example, in comedies, a person with muscle tics may haplessly raise their hand at an obviously inappropriate time and suffer the consequences. This is implausible: tics are semi-voluntary actions to alleviate the feeling of an unwanted, premonitory urge. One would not thrust his or her arm in the air as in Alien hand syndrome.
Tics must be distinguished from fasciculations. Small twitches of the upper or lower eyelid, for example, are not tics because they don't involve a whole muscle. They are twitches of a few muscle fibre bundles, which you can feel but barely see.
Motor tic is considered an absolute contraindication to the use of the following medications:
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