Epidemiology
- Onset age < 18 (commonly age 6-15)
Etiology
- Comorbidities (High-Yield):
- ADHD (~50–60%): Most common comorbid disorder.
- OCD (~30–40%): Second most common comorbid condition.
- Anxiety, depression, and learning disabilities.
Pathophysiology
- Exact mechanism unknown; strong genetic component (highly heritable).
- Involves dysregulation of the cortico-striato-thalamo-cortical circuitry.
- Excess dopaminergic transmission in the basal ganglia (caudate nucleus). t
- Associated with disinhibition of the motor and limbic system loops.
Clinical features
- Diagnostic triad components:
- Multiple motor tics (e.g., blinking, grimacing, shoulder shrugging, head jerking).
- ≥1 vocal/phonic tic (e.g., grunting, throat clearing, sniffing, snorting).
- Temporal criteria:
- Present for >1 year (frequency may wax and wane).
- Onset before age 18.
- Associated phenomena:
- Premonitory urge: Sensation of tension/discomfort preceding the tic, temporarily relieved following tic execution.
- Suppressibility: Can be consciously suppressed for brief periods (leads to rebound increase).
- Coprolalia: Involuntary utterance of obscene words (only ~10–20% of cases; high-yield board buzzword).
- Copropraxia: Involuntary obscene gestures.
- Echolalia (repeating others’ words) / Palilalia (repeating one’s own words).
- Triggers: Exacerbated by emotional stress, fatigue, excitement, and illness; attenuated during focused, absorbing activities.
Diagnostics
DDx
- Stereotypic movement disorder
- Characterized by simple repetitive movements (eg, rocking, head banging), which are voluntary in nature and seemingly purposeless.
- They are often seen in children with autism spectrum disorders and intellectual disability and are a common form of self-soothing.
Treatment
Tip
Pharmacotherapy is very similar to Huntington disease.
- Mild / Non-impairing:
- Psychoeducation, watchful waiting, behavioral support, and classroom accommodations.
- First-Line / Behavioral Therapy (Mild-to-Moderate Impairment):
- Comprehensive Behavioral Intervention for Tics (CBIT) / Habit Reversal Therapy (HRT).
- First-Line Pharmacotherapy (Preferred initial med):
- Alpha-2 adrenergic agonists: Guanfacine or Clonidine (preferred first-line due to low side-effect profile; especially effective if comorbid ADHD).
- Second-Line Pharmacotherapy (Moderate-to-Severe Impairment):
- Refractory / Severe Cases:
- First-Generation Antipsychotics (FGAs): Haloperidol, Pimozide (FDA-approved; limited by risk of EPS, tardive dyskinesia, and QTc prolongation).
- Deep Brain Stimulation (DBS): Reserved for severe, medically refractory adult cases.