Tic Disorders and Twitches
What Are Tics and Twitches? continued...
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.
What Are the Common Tic Disorders?
The majority of tics are not severe. So they have very little effect on a person's quality of life. In some instances, though, tics may occur often enough to be disruptive and troubling. When they do, they can affect many areas of a person's life, including school, work, and social life.
Doctors use four characteristics to identify and diagnose tic disorders:
- the age when tics began
- duration of the tics
- severity of the tics
- whether tics are motor or vocal or both
Transient tic disorder. This disorder most commonly appears in youth. It affects between 5% and 25% of school-age children. Transient tic disorder is characterized by the presence of one or more tics for at least one month but less than one year. The majority of tics seen in this disorder are motor tics, though vocal tics may also be present.
Many children with the disorder experience multiple episodes of the transient tics, which may vary in how they manifest over time.
Chronic motor or vocal tic disorder. While transient tics disappear within a year, chronic tics can last for a year or more. Chronic tic disorder is characterized by the presence of one or more long-lasting tics. They may be either motor or vocal, but not both. For a diagnosis of chronic tic disorder, symptoms must begin before age 18.