Tics are sudden twitches, movements, or sounds that people do repeatedly. People who have tics cannot stop their body from doing these things. For example, a person with a motor tic might keep blinking over and over again. Or, a person with a vocal tic might make a grunting sound unwillingly.
While many people use the terms tic and twitch interchangeably, there are differences between these two forms of movements.
Tics. There are two types of tics -- motor tics and vocal tics. These short-lasting sudden movements (motor tics) or uttered sounds (vocal tics) occur suddenly during what is otherwise normal behavior. Tics are often repetitive, with numerous successive occurrences of the same action. For instance, someone with a tic might blink their eyes multiple times or twitch their nose repeatedly.
Motor tics can be classified as either simple or complex. Simple motor tics may include movements such as eye-blinking, nose-twitching, head-jerking, or shoulder-shrugging. Complex motor tics consist of a series of movements performed in the same order. For instance a person might reach out and touch something repeatedly or kick out with one leg and then the other.
Tics are often classified not as involuntary movements but as unvoluntary movements. This means that people are able to suppress the actions for a time. The suppression, though, results in discomfort that grows until it is relieved by performing the tic.
While people of all ages can experience tics, they are most prevalent in children. Experts say that around 20% of children experience tics. And tics are far more likely to affect boys than girls.
No one knows exactly what causes tics to occur. Stress and sleep deprivation seem to play a role in both the occurrence and severity of motor tics.
Twitches. Unlike tics, the majority of muscle twitches are isolated occurrences, not repeated actions. Muscle twitches are also known as myoclonic jerks. They are entirely involuntary and cannot be controlled or suppressed.
One type of muscle twitch is benign essential blepharospasm. Blepharospasm refers to the muscles of one or both eyelids twitching uncontrollably. This often occurs repeatedly over a sustained period of time. In extreme cases, which are rare, benign essential blepharospasm may also involve the eyebrows, mouth, and neck.
While an eyelid twitch may mimic an eye-blinking tic, it is different because it cannot be controlled. It also occurs most often in adults. Your doctor may be able to determine whether you or your child is experiencing tics or an eyelid twitch based upon the symptoms.
Experts believe that the eyelid twitching of blepharospasm is caused by the misfiring of certain cells in one area of the brain. Eyelid twitches may be aggravated by having dry eyes. They may also be worsened by stress, lack of sleep, caffeine, and harsh light conditions.
The defining symptom of tic disorders is the presence of one or more tics. These tics can be classified as:
Tics can also be divided into the following categories:
Tics are usually preceded by an uncomfortable urge, such as an itch or tingle. While it is possible to hold back from carrying out the tic, this requires a great deal of effort and often causes tension and stress. Relief from these sensations is experienced upon carrying out the tic.
The symptoms of tic disorders may:
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The American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)1 is used by health professionals to help diagnose tic disorders.
Three tic disorders are included in the DSM-5:
The tic disorders differ from each other in terms of the type of tic present (motor or vocal, or a combination of both), and how long the symptoms have lasted. People with TS have both motor and vocal tics, and have had tic symptoms for at least 1 year. People with persistent motor or vocal tic disorders have either motor or vocal tics, and have had tic symptoms for at least 1 year. People with provisional tic disorders can have motor or vocal tics, or both, but have had their symptoms less than 1 year.
Here are the criteria in shortened form. Please note that they are presented for your information only and should not be used for self-diagnosis. If you are concerned about any of the symptoms listed, you should consult a trained healthcare provider with experience in diagnosing and treating tic disorders.
To be diagnosed with TS, a person must:
Persistent (Chronic) Motor or Vocal Tic Disorder
To be diagnosed with a persistent tic disorder, a person must:
Transient tic disorder, now known as provisional tic disorder, is a condition involving physical and verbal tics.
To be diagnosed with a provisional tic disorder, a person must:
In some children, tics may suddenly appear, or suddenly become worse, following a streptococcal (strep) infection, such as strep throat or scarlet fever.
· Echopraxia: repeat movement of others
· Copropraxia: obscene gestures
· Echolalia: repeating last words from others
· Palilalia: repeat own words
· Coprolalia: inappropriate words
The exact cause of tic disorders is unknown. Within Tourette’s research, recent studies have identified some specific gene mutations that may have a role. Brain chemistry also seems to be important, especially the brain chemicals glutamate, serotonin, and dopamine.
Tics that have a direct cause fit into a different category of diagnosis. These include tics due to:
In addition, tics can be associated with more serious medical disorders, such as Huntington’s disease or Creutzfeldt-Jakob disease.