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Infantile Spasms (West Syndrome): Recognition, Causes, and Urgent Treatment

Understanding Infantile Spasms

Infantile spasms (IS)—the hallmark of West syndrome—are a catastrophic epileptic encephalopathy of infancy. Early recognition and treatment within weeks of onset dramatically improve neurodevelopmental outcomes. Incidence: ~2–3.5 per 10,000 live births. Peak onset: 4–8 months.

Clinical Features

  • Spasm semiology: Sudden, symmetric flexion/extension of trunk, neck, arms (flexor: "jackknife"; extensor: "self-hug"; mixed). Duration: 1–3 seconds. Occur in clusters (5–100+) upon waking or drowsiness.
  • Associated features: Developmental arrest/regression, irritability, feeding difficulties, autonomic changes (flushing, apnea).
  • EEG: Hypsarrhythmia—chaotic, high-voltage, multifocal spikes with electrodecremental events. Pathognomonic but not universal (modified patterns exist).

Etiologies (Structural/Genetic/Metabolic)

  • Structural: HIE, stroke, cortical malformations (lissencephaly, polymicrogyria), TSC (tuberous sclerosis—up to 50% develop IS), trauma
  • Genetic: ARX, STXBP1, KCNQ2, SCN2A, CDKL5, SLC25A22, >100 genes
  • Metabolic: Nonketotic hyperglycinemia, pyridoxine dependency, biotinidase deficiency, mitochondrial disorders
  • Infectious: CMV, HSV, Zika, congenital syphilis
  • Cryptogenic: No identifiable cause (~15–30%)

Urgent Diagnostic Workup

  1. Video-EEG (prolonged, including sleep)—confirm hypsarrhythmia/spasms
  2. Brain MRI (epilepsy protocol, 3T preferred)—structural etiology
  3. Genetic panel / exome sequencing—highest yield
  4. Metabolic labs: Amino acids, organic acids, lactate, pyruvate, CSF neurotransmitters, glycine
  5. Infectious workup if indicated

First-Line Treatment (Time-Sensitive)

  • ACTH (corticotropin): High-dose (150 U/m²/day IM) × 2–3 weeks, then taper. Gold standard; ~60–70% spasm freedom.
  • Oral high-dose prednisolone: 40–60 mg/day (2–3 mg/kg/day) × 2 weeks, taper. Comparable efficacy; more accessible. Preferred in many centers.
  • Vigabatrin (Sabril): First-line for TSC-associated IS (70–90% response). Risk: irreversible concentric visual field loss (30–50%). Mandatory baseline + serial ERG/visual fields. Not first-line for non-TSC in US.

Second-Line and Adjunctive

  • Ketogenic diet, topiramate, zonisamide, levetiracetam, pyridoxine (if metabolic), cannabidiol (emerging)
  • Epilepsy surgery for focal structural lesions (hemispherectomy, focal resection)

Prognosis Determinants

  • Time to treatment: Each week of delay ↓ developmental quotient
  • Etiology: TSC, structural > cryptogenic > genetic (variable)
  • Hypsarrhythmia resolution correlates with outcome
  • Developmental status at onset

Critical Action

If you suspect infantile spasms: Record video → ER/pediatric neurologist TODAY. Do not wait for "next available appointment." This is a neurodevelopmental emergency.

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