A tic is a sudden, rapid, repetitive movement (motor tic) or vocalization (vocal tic).
There are two main types of tics:
Simple tics involve one muscle group
Simple motor tics include head shaking, eye blinking, sniffing, neck jerking, shoulder shrugging and grimacing. These are more common.
Simple vocal tics include coughing, throat clearing and barking.
Complex tics involve more than one muscle group
Complex motor tics include self-hitting or self-biting, jumping and hopping, and twirling while walking.
Complex vocal tics include repeating words out of context, echoing what someone else said and speaking obscenities.
Tics sometimes change over time from one simple type of tic to another or from a simple to a complex tic. Some tics are slow and sustained rather than brief and rapid. Some involve the lower body.
Tics are thought to be inherited neurological disorders that affect the body's motor system. They also can be caused by head injury or certain drugs, such as stimulants.
People with tic disorders describe an urge building up inside them before the tic appears. This buildup feeling is called a premonition. People with tics often feel relief after the tic is over.
Although tics are involuntary, tics cease during sleep and the urge sometimes can be suppressed for short periods with effort. After making an effort to suppress a tic, the person usually has a burst of tics to relieve a buildup of the inner sensation. To get some idea of what this is like, try not blinking for as long as you can. You'll feel a buildup sensation the longer you don't blink, and you'll feel great relief when you finally do blink.
When both motor and vocal tics are present and last for more than one year, the disorder is named Tourette's syndrome. A number of other disorders often occur along with tic symptoms. For example, more than 50% of people with Tourette's syndrome also have attention-deficit hyperactivity disorder, and approximately 30% to 40% also have obsessive-compulsive disorder.