Many people at some point experience spasm-like movements of particular muscles. These movements, known as tics and twitches, often affect the eyelids or face. They can, though, occur anywhere in the body.
In most instances, tics and twitches are harmless and temporary. In some cases, though, they may be caused by a tic disorder. Tic disorders generally can be managed with treatment and lifestyle changes.
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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 his eyes multiple times or twitch her 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 25% 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.
Doctors once believed that certain medications, including some used to treat attention deficit hyperactivity disorder, induced tics in children that were prone to them. Newer studies, though, suggest this is not the case.
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.