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- A tic is a sudden, repetitive, stereotyped, involuntary movement (e.g., blinking, grimacing) or vocalization (e.g., throat clearing, sniffing). Tics can be further classified as simple (e.g., nose twitching, grunting) or complex (e.g., hand gestures, jumping, echolalia). Tics characteristically change in anatomic location, frequency, type, complexity, and severity over time, although each tic has a stable appearance from one occurrence to the next. Most individuals are able to suppress their tics for brief periods of time, and some endorse having premonitory sensory urges that precede their tics. Tics typically abate during sleep but can persist in some cases.
- DSM-5 classification of tic disorders:
- Tourette syndrome (TS): Both ≥2 motor and ≥1 vocal tics have been present at some time, although not necessarily concurrently; tics have been present for >1 year since first tic onset (regardless of the duration of tic-free periods); onset <18 years
- Persistent (chronic) motor or vocal tic disorder: ≥1 motor or vocal tics but not both; tics have been present for >1 year since first tic onset; onset <18 years
- Provisional tic disorder: ≥1 motor and/or vocal tics; tics have been present for <1 year since first tic onset; onset <18 years
- Other specified tic disorder: tics causing clinically significant distress or impairment but not meeting the full criteria for a tic disorder. Provider should specify the atypical feature(s), for example, “with onset after age 18 years.”
- Unspecified tic disorder: as above, but provider chooses not to specify the reason that full criteria for a tic disorder are not met (e.g., there is insufficient information to make a more specific diagnosis)
- When there is evidence of an underlying organic etiology, a diagnosis of “other specified tic disorder” should be used.
- Pediatric autoimmune neuropsychiatric disorder associated with Streptococcus (PANDAS): a controversial entity first described in 1998. In theory, group A β-hemolytic streptococcal (GABHS) infection triggers antibodies that cross-react with the basal ganglia and cause obsessive-compulsive disorder (OCD) symptoms and/or tics in some individuals. The National Institute of Mental Health defines PANDAS as follows:
- Presence of OCD and/or a tic disorder
- Prepubertal onset
- Sudden, explosive onset of symptoms and a course of dramatic exacerbations and remission
- Temporal relationship between symptom onset and exacerbations and GABHS infections
- Presence of neurologic abnormalities (hyperactivity, choreiform movements, tics) during exacerbations
- These diagnostic criteria do not always prove helpful in distinguishing PANDAS from other “standard” tic disorders. The high incidence of GABHS infections and high prevalence of asymptomatic carriers make it difficult to prove a link between GABHS infection and tics.
- Other autoimmune neuropsychiatric conditions with less restrictive diagnostic criteria have been proposed, including Pediatric Acute-Onset Neuropsychiatric Syndrome (PANS) and Childhood Acute Neuropsychiatric Symptoms (CANS).
- Described in almost all ethnic groups
- Affects males > females
- Typical onset is between ages 5 and 7 years.
- The prevalence of chronic tics and TS in school-age children is 3–6% and 0.1–1%, respectively.
- Transient tics occur in 20–25% of children.
No single gene has been associated with tics or TS; however, the family history is often positive for tics. The prevalence of TS in 1st-degree relatives is 10 times that in the general population.
Tics cannot be prevented, but educating patients, families, and school personnel about tics can minimize their impact. Aggressive management of comorbid conditions strongly influences patient outcomes.
The pathophysiology underlying tics and TS is not completely understood but is thought to involve abnormal dopamine neurotransmission within the basal ganglia. Evidence also implicates problems with serotonin, norepinephrine, and acetylcholine.
Theory: Environmental or hormonal perturbations trigger tics in genetically susceptible individuals.
Commonly Associated Conditions
- ∼50% of children with chronic motor tics or TS meet diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD), and ∼50% have OCD or obsessive-compulsive traits.
- Anxiety, learning disabilities (LD), oppositional defiant disorder, conduct disorder, and rage episodes are also associated with TS.