Tics

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Basics

Description

  • Tics are sudden, repetitive, patterned movements (e.g., blinking, grimacing, gesturing) or vocalizations (e.g., throat clearing, grunting, shouting words). Tics may occur sporadically for short periods on one or more occasions during childhood or they may persist for months to years. When they persist, tics characteristically change in anatomic location, frequency, type, complexity, and severity. Multiple concurrent tics may occur. Most older children are able to suppress their tics for brief periods of time and endorse having premonitory sensory urges that precede at least some of their tics. Tics tend not to interrupt continuous purposeful movements in the same muscle group. Tics may increase during stress or relaxation. Tics typically diminish or stop during engagement in performance of skilled activities and during sleep.
  • DSM-5 classification of tic disorders:
    • Tourette disorder also known as 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:
      • Designates ≥1 year of either motor or vocal tics but not both (Note subtle vocal tics such as throat clearing are easily overlooked; thus, most cases are actually TS.)
      • 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
    • Note: When tics occur secondary to other brain processes (via induction by medications, after brain injury, as part of autoimmune Sydenham chorea, or as part of Wilson or other degenerative diseases), the diagnosis of TS should not be used.
  • Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS)/pediatric acute-onset neuropsychiatric syndrome (PANS):
    • PANDAS has recently been subsumed under the broader (in etiology as well as symptoms) and less specific umbrella of PANS. As tics are now a minor criterion, this discussion lies outside the scope of this section.

Epidemiology

  • Described in almost all ethnic groups
  • Affects males > females
  • Typical onset is between ages 3 and 10 years.

Prevalence

  • The prevalence of tics in school-age children is 6–12%, with transient tics occurring in 20–25% at some time during childhood.
  • The prevalence of TS is 0.5–1% in school-age children.

Risk Factors

Genetics

A positive family history of tics and/or obsessive-compulsive disorder (OCD), with a pattern often consistent with autosomal dominant transmission is very common. Incomplete penetrance frequently occurs, with greater penetrance in males. However, genetics are complex, with large cohort genetic studies demonstrating that a large number of genes exert small effects.

General Prevention

Tics cannot be prevented.

Pathophysiology

The pathophysiology underlying tics and TS is thought to involve genetically influenced abnormalities in dopamine neurotransmission within the basal ganglia and/or cortex. Evidence also implicates differences in signaling involving gamma-aminobutyric acid (GABA), serotonin, and possibly norepinephrine in prefrontal brain regions. Environmental processes and unknown age- and sex-dependent factors may play a role in symptom induction and expression.

Etiology

Unknown. Is highly heritable but not contagious. Increased tic severity can occur acutely with psychosocial stresses.

Commonly Associated Conditions

  • The majority of children with TS have associated comorbid conditions, with attention-deficit/hyperactivity disorder (ADHD) and OCD most frequently present.
  • Anxiety, learning disabilities (LD), oppositional defiant disorder, conduct disorder, and rage episodes are also common in TS.

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