What are the causes of tics in children and adolescents?

Causes of Tics in Children and Adolescents

Primary Etiology: Tourette Syndrome and Related Tic Disorders

The vast majority of tics in children are idiopathic, representing primary tic disorders along a spectrum from transient tic disorder to Tourette syndrome, with strong genetic predisposition and environmental modulation. 1, 2

Genetic Factors

• First-degree relatives of individuals with chronic tic disorders have significantly elevated risk, indicating strong familial inheritance patterns 3, 4
• Multiple genes are implicated, including both low-effect and larger-effect variants, particularly single nucleotide polymorphisms (SNPs) in the SLITRK1 gene 3, 5
• Boys are affected approximately 3-4 times more commonly than girls, with prevalence of approximately 1 per 1,000 male children 1, 2

Environmental and Perinatal Factors

• Pre- and perinatal complications including low birth weight, intrauterine growth retardation, and maternal stress during pregnancy 3, 4
• Group A Streptococcal (GAS) infections and other infectious triggers may precipitate or exacerbate tics in genetically predisposed individuals 4
• Psychosocial stress can trigger onset or worsen existing tics 4

Secondary Causes of Tics

Neurological Insults to Basal Ganglia

• Head trauma (2.5% of tic cases in one series) 6
• Stroke affecting basal ganglia structures (1.2%) 6
• Encephalitis and other central nervous system infections (1.9%) 6
• Static encephalopathy from various causes 6

Drug-Induced Tics

• Sympathomimetic drugs (stimulants) may precipitate or unmask tic disorders in predisposed individuals 7
• Various other medications and toxins can trigger secondary tics 6

Neurodevelopmental and Genetic Disorders

• Pervasive developmental disorders including Asperger's syndrome (8.3%), autism (1.9%), and mental retardation (2.5%) 6
• Chromosomal abnormalities such as Down syndrome (3.2%) 6
• Neurodegenerative conditions including neuroacanthocytosis (1.2%) and Huntington's disease (0.6%) 6

Post-Infectious/Autoimmune

• Autoimmune response to microbial antigens, particularly following streptococcal infections, may contribute to tic onset and exacerbation 4
• Post-infectious mechanisms involving immune dysregulation 3, 4

Peripheral Injury

• Rarely, peripheral nerve injury can trigger movement disorders including tics (0.6%) 6

Psychogenic Tics

• Functional/psychogenic tics account for approximately 10% of cases presenting to movement disorder clinics 6
• These require extensive evaluation to distinguish from primary tic disorders 1

Pathophysiological Mechanism

The cortical-basal ganglia-thalamocortical circuit is implicated in tic generation, though the primary location and neurotransmitter abnormalities remain controversial 5. The interaction between genetic vulnerability and environmental triggers creates neurobiological susceptibility to tic development 3, 4.

Critical Diagnostic Considerations

Distinguish Primary from Secondary Tics

• Transient tic disorder (4-24% of elementary school children) resolves within one year and is far more common than chronic tic disorders 1, 2
• Chronic tic disorders persist beyond one year but may involve only motor OR vocal tics 2, 8
• Tourette syndrome requires multiple motor tics AND at least one vocal tic persisting for at least one year with childhood onset 1, 2

Key Clinical Features Supporting Primary Tic Disorder

• Suppressibility: Ability to temporarily suppress tics voluntarily, followed by intensification of premonitory sensation 2, 8
• Waxing-waning pattern: Fluctuation in tic severity over weeks to months 2, 8
• Premonitory sensations: Uncomfortable urge preceding tic execution 1, 8
• Distractibility and suggestibility: Tics can be modified by attention and suggestion 8

Avoid Diagnostic Pitfalls

• Do not perform excessive medical testing for typical primary tic presentations, as diagnosis is primarily clinical and unnecessary testing causes iatrogenic harm 1, 2
• Do not misdiagnose tics as "habit behaviors" or "psychogenic symptoms" without thorough evaluation, as this leads to inappropriate interventions 1, 2, 8
• Replace outdated terminology: use "tic cough" instead of "habit cough" and "somatic cough disorder" instead of "psychogenic cough" 1