Tic - Description and Classification

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, fatigue, boredom, 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 increase (for instance, watching television or using a computer), while concentration on an absorbing activity often leads to a decrease in tics. Neurologist and writer Oliver Sacks described 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 remitted almost completely while he was 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 that 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.