Tics are muscle movements that occur repeatedly in brief, sudden uncontrollable spasms. They often involve muscles of the face and eyes. The tic is the same each time it occurs, and stress worsen tics. During periods of intense mental concentration, tics occur less often. While stress is a contributing factor to most tics and twitches, insufficient lubrication of the eyes by tears may also play a role.
Tics affect as many as one-fourth of all children at some time. More boys than girls are affected. Short lived or transient tics are common in childhood and may appear and disappear within a few weeks or months. Many times, children with tics also have attention deficit disorder and other behavioral difficulties, including speech problems and obsessive-compulsive symptoms. These behaviors are often more impairing than the tics and are frequently the reason that treatment is sought.
Tics may be caused by severe stress, some medications and on rare occasions, some infections that involve the brain (encephalitis) and viral infections. Streptococcal infections have been associated with the development of tics and obsessive-compulsive behaviors.
Another type of tic also exists – the chromic motor tic disorder. This type of tic may last for years. There are several forms of tics. Some of the most common manifestations of ticks are:
Eye blinking or squinting
Twitching of the eye or mouth
Wrinkling-up of the nose
Mouth twitching
Repetitive clearing of the throat
Head twitching
Shrugging the shoulders
Some tics are complex muscle movements, such as flapping the arms or pulling at the clothes.
The cause of tics is unknown, but the vulnerability to tic disorders appears to be genetic or transmitted within families. Genetic factors are present in 75% of cases, though no single gene has been found to cause tic disorders. Researchers have not found a pattern that suggests that certain parenting types or childhood experiences lead to the development of tic disorders. Some researchers think that there is an interaction between genetic and environmental factors. They are now paying close attention to prenatal factors which are thought to influence the development of the disorder.
Some tics develop or are triggered by the environment. A cough that began during a respiratory infection may continue as an involuntary vocal tic. New tics may also begin as imitations of normally occurring events like mimicking a dog barking. It is unknown how these particular things come to form enduring symptoms.
The diagnostic criteria of all tic disorders specify that the symptoms must appear before the age of 18 and that they cannot result from ingestion of any substances such as stimulants or from other general medical conditions.
Motor and vocal tics may be worsened by anxiety, stress, boredom, fatigue or excitement. Some people have reported that tics are intensified by additives in food, stimulants and PMS. Marijuana, alcohol, relaxation, playing a sport, or concentrating on a task that is enjoyed reduces the severity and frequency of their symptoms.
There appears to be both functional and structural abnormalities in the brains of people with tic disorders.
The exact neurochemical cause is unknown, but it is believed that abnormal chemical messengers within the brain contribute to the disorder. The affected chemicals are dopamine and serotonin. Also abnormal blood flow has been shown in computerized tomography.
Most tics are not harmful, but sometimes they may indicate a more serious problem. Special techniques to change behaviors may help treat tic disorders. Counseling may uncover emotional causes and help deal with problems caused by tics. Minor tics may respond to mild sedatives or other medications.
