Tic disorders: Causes, types, and diagnosis
Movements of the limbs and other body parts are known as motor tics. Involuntary repetitive sounds, such as grunting, sniffing, or throat clearing, are called vocal tics.
Many cases of tics are temporary and resolve within a year. However, some people who experience tics develop a chronic disorder. Chronic tics affects about 1 out of 100.
Types of tics disorders
Tic disorders can usually be classified as motor, vocal, or Tourette's syndrome, which is a combination of both.
Motor and vocal tics can be short-lived (transient) or chronic. Tourette's is considered to be a chronic tic disorder.
Transient tic disorder
Transient tic disorder occurs for less than 1 year, and are more commonly motor tics.
According to the American Academy of Child and Adolescent Psychiatry, transient tic disorder or provisional tic disorder affects up to 10 percent of children during their early school years.
Children with transient tic disorder will present with one or more tics for at least 1 month, but for less than 12 consecutive months. The onset of the tics must have been before the individual turned 18 years of age.
Motor tics are more commonly seen in cases of transient tic disorder than vocal tics. Tics may vary in type and severity over time.
Some research suggests that tics are more common among children with learning disabilities and are seen more in special education classrooms. Children within the autism spectrum are also more likely to have tics.
Chronic motor or vocal tic disorder
Tics that appear before the age of 18 and last for 1 year or more may be classified as a chronic tic disorder. These tics can be either motor or vocal, but not both.
Chronic tic disorder is less common than transient tic disorder, with less than 1 percent of children affected.
If the child is younger at the onset of a chronic motor or vocal tic disorder, they have a greater chance of recovery, with tics usually disappearing within 6 years. People who continue to experience symptoms beyond age 18 are less likely to see their symptoms resolved.
Tourette's syndrome (TS) is a complex neurological disorder. It is characterized by multiple tics - both motor and vocal. It is the most severe and least common tic disorder.
The Centers for Disease Control and Prevention (CDC) report that the exact number of people with TS is unknown. CDC research suggests that half of all children with the condition are not diagnosed. Currently, 0.3 percent of children aged 6 to 17 in the United States have been diagnosed with TS.
Symptoms of TS vary in their severity over time. For many people, symptoms improve with age.
The defining symptom of tic disorders is the presence of one or more tics. These tics can be classified as:
- Motor tics: These include tics, such as head and shoulder movements, blinking, jerking, banging, clicking fingers, or touching things or other people. Motor tics tend to appear before vocal tics, although this is not always the case.
- Vocal tics: These are sounds, such as coughing, throat clearing or grunting, or repeating words or phrases.
Tics can also be divided into the following categories:
- Simple tics: These are sudden and fleeting tics using few muscle groups. Examples include nose twitching, eye darting, or throat clearing.
- Complex tics: These involve coordinated movements using several muscle groups. Examples include hopping or stepping in a certain way, gesturing, or repeating words or phrases.
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.
Anxiety, anger, and fatigue may make the symptoms of a tic disorder worse.
The symptoms of tic disorders may:
- worsen with emotions, such as anxiety, excitement, anger, and fatigue
- worsen during periods of illness
- worsen with extreme temperatures
- occur during sleep
- vary over time
- vary in type and severity
- improve over time
Causes and risk factors
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:
- head injuries
- other injuries
Risk factors for tic disorders include:
- Genetics: Tics tend to run in families, so there may be a genetic basis to these disorders.
- Sex: Men are more likely to be affected by tic disorders than women.
Conditions associated with tic disorders, especially in children with TS, include:
- autism spectrum disorder
- learning difficulties
- speech and language difficulties
- sleep difficulties
Other complications associated with tic disorders are related to the effect of the tics on self-esteem and self-image.
Some research has found that children with TS or any chronic tic disorder experience a lower quality of life and lower self-esteem than those without one of these conditions.
In addition, the Tourette Association of America say that people with TS often experience difficulties with social functioning due to their tics and associated conditions, such as ADHD or anxiety.
Tic disorders are diagnosed based on signs and symptoms. The child must be under 18 at the onset of symptoms for a tic disorder to be diagnosed. Also, the symptoms must not be caused by other medical conditions or drugs.
The criteria used to diagnose transient tic disorder include the presence of one or more tics, occurring for less than 12 months in a row.
Chronic motor or vocal tic disorders are diagnosed if one or more tics have occurred almost daily for 12 months or more. People with a chronic tic disorder that is not TS, will experience either motor tics or vocal tics, but not both.
TS is based on the presence of both motor and vocal tics, occurring almost daily for 12 months or more. Most children are under the age of 11 when they are diagnosed. Other behavioral concerns are often present, as well.
To rule out other causes of tics, a doctor may suggest:
- blood tests
- MRI scans or other imaging
Treatment and coping
Treatment depends on the type of tic disorder and its severity. In many cases, tics resolve on their own without treatment.
Severe tics that interfere with daily life may be treated with therapies, medications, or deep brain stimulation.
Therapies for tic disorders
Some types of cognitive behavioral therapy can help people manage the discomfort of a tic disorder.
Some therapies are available to help people control tics and reduce their occurrence, including:
- Exposure and response prevention (ERP): A type of cognitive behavioral therapy that helps people become accustomed to the uncomfortable urges preceding a tic, with the aim of preventing the tic.
- Habit reversal therapy: A treatment that teaches people with tic disorders to use movements to compete with tics, so the tic cannot happen.
Medication can be used alongside therapies or on its own. Medication typically reduces tic frequency, but does not completely get rid of the symptoms. Available medications include:
- anti-seizure medications
- Botox injections
- muscle relaxants
- medications that interact with dopamine
Other medications may help symptoms associated with tic disorders. For example, antidepressants can be prescribed for symptoms of anxiety and OCD.
Deep brain stimulation
Deep brain stimulation (DBS) is an option for people with TS whose tics do not respond to other treatments and impact someone's quality of life.
DBS involves the implantation of a battery-operated device in the brain. Certain areas of the brain that control movement are stimulated with electrical impulses with the aim of reducing tics.
Coping and self-help tips
Some lifestyle changes can help reduce the frequency of tics. They include:
- avoiding stress and anxiety
- getting enough sleep
It can be helpful to:
- join a support group for people with TS and other tic disorders
- reach out to friends and others for help and support
- remember that tics tend to improve or disappear with age
Parents of children with tics may wish to:
- inform teachers, caregivers, and others who know the child, about the condition
- help boost the child's self-esteem by encouraging interests and friendships
- ignore times when a tic occurs, and avoid pointing it out to the child