Common Movement Disorders in Children

1. Definition and Classification

Movement disorders are neurological conditions characterized by an abnormality in the speed, fluency, or smoothness of voluntary movement. In pediatrics, they are predominantly Hyperkinetic (excessive movement).

Broad Classification:

1. Hyperkinetic (Excessive): Tics, Chorea, Dystonia, Myoclonus, Tremor, Stereotypies.
2. Hypokinetic (Reduced): Parkinsonism (rare in children; e.g., Juvenile Parkinsonism, drug-induced).
3. Ataxic: Disorders of coordination (Cerebellar).

2. Common Hyperkinetic Disorders

A. Tics (Most Common)

• Definition: Brief, sudden, recurrent, non-rhythmic, stereotyped motor movements or vocalizations.
• Key Features:
  • Premonitory Urge: A sensation of building tension before the tic.
  • Suppressibility: Can be voluntarily suppressed for short periods (unlike chorea/myoclonus).
  • Variable: Wax and wane in frequency and severity.
• Types:
  • Transient Tic Disorder: < 1 year.
  • Chronic Tic Disorder: > 1 year (motor or vocal).
  • Tourette Syndrome: Multiple motor + at least one vocal tic, lasting > 1 year.

B. Chorea

• Definition: Involuntary, irregular, purposeless, random, flowing movements that flit from one body part to another ("Dance-like").
• Key Features:
  • Milkmaid’s Grip: Inability to maintain sustained grip.
  • Darting Tongue: Inability to keep tongue protruded (Jack-in-the-box tongue).
  • Piano-playing fingers: When hands are outstretched.
• Common Etiologies:
  • Sydenham’s Chorea: (St. Vitus Dance) Post-streptococcal autoimmune disorder (Rheumatic Fever).
  • Wilson’s Disease: Treatable metabolic cause (check Ceruloplasmin).
  • SLE / Antiphospholipid Syndrome.

C. Dystonia

• Definition: Sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or twisting.
• Key Features:
  • Sensory Trick (Geste antagoniste): Touching a specific body part (e.g., chin) temporarily relieves the posture.
  • Task-specific: E.g., Writer's cramp.
• Types:
  • Focal: Torticollis, Blepharospasm.
  • Generalized: DYT1 mutation.
  • Dopa-Responsive Dystonia (Segawa Disease): Diurnal variation (worse in evening), responds dramatically to Levodopa.

D. Tremor

• Definition: Rhythmic, oscillatory movement of a body part produced by alternating contractions of agonist and antagonist muscles.
• Types:
  • Physiologic: Enhanced by anxiety, thyrotoxicosis, caffeine, beta-agonists (asthma inhalers).
  • Essential Tremor: Action tremor, often familial.
  • Resting Tremor: Rare in kids (Juvenile Parkinsonism, Wilson's).
  • Rubral/Holmes Tremor: Slow, coarse tremor (Midbrain lesion).

E. Myoclonus

• Definition: Sudden, brief, shock-like jerks caused by muscle contraction (positive) or inhibition (negative/asterixis).
• Types:
  • Physiologic: Hypnic jerks (sleep starts).
  • Epileptic: Juvenile Myoclonic Epilepsy (JME), SSPE (Subacute Sclerosing Panencephalitis).
  • Opsoclonus-Myoclonus Syndrome: "Dancing eyes, dancing feet" (Paraneoplastic - Neuroblastoma).

F. Stereotypies

• Definition: Rhythmic, repetitive, fixed, purposeless movements.
• Key Features: Occur during excitement, stress, or boredom. Can be stopped with distraction (unlike tics which have an urge).
• Examples: Hand flapping, body rocking, head banging.
• Association: Autism Spectrum Disorder (ASD), but also common in normal children ("Physiologic Stereotypies").

3. Functional (Psychogenic) Movement Disorders

• Common in adolescents.
• Features: Abrupt onset, distractibility, entrainment (movement changes frequency to match the examiner's tapping), and variability.

4. Summary of Clinical Differentiators