What are West syndrome and Lennox‑Gastaut syndrome?

West Syndrome and Lennox-Gastaut Syndrome: Clinical Definitions

West syndrome and Lennox-Gastaut syndrome are two distinct but related severe epileptic encephalopathies of childhood that represent age-dependent manifestations of catastrophic epilepsy, with West syndrome occurring in infancy and Lennox-Gastaut syndrome typically emerging in early childhood, often as a progression from West syndrome.

West Syndrome

West syndrome is an epileptic encephalopathy that presents in infancy with three cardinal features 1:

• Infantile spasms (clustered seizures)
• Hypsarrhythmia on EEG (chaotic, high-amplitude slow waves with multifocal spikes)
• Developmental arrest or regression

Key Clinical Characteristics:

• Onset: Usually before 1 year of age
• Incidence: 1:3,200 live births 1
• Prognosis: Aetiology-dependent; up to 80% of children with symptomatic West syndrome develop mental retardation 1
• Evolution: Approximately 25-60% of cases evolve to Lennox-Gastaut syndrome, though some studies report lower rates (10.7%) with specific treatments 2, 3

Lennox-Gastaut Syndrome (LGS)

Lennox-Gastaut syndrome is a severe developmental and epileptic encephalopathy characterized by 4, 5, 6:

Defining Features:

• Multiple seizure types (must include tonic seizures)
  • Drop attacks (tonic or atonic seizures) are particularly dangerous and lead to frequent injuries
  • Atypical absence seizures
  • Myoclonic seizures
  • Generalized tonic-clonic seizures
• Abnormal EEG: Generalized slow (<3 Hz) spike-wave discharges 5
• Cognitive impairment and behavioral disturbances
• Classical onset: Before 8 years of age (though later onset cases exist) 6

Clinical Burden:

Patients experience many seizures daily, with some seizure types (like atypical absence) being difficult to count 4. The drop attacks are among the most dangerous seizure types, frequently causing injuries and significantly impairing quality of life 4.

Treatment Challenges:

• Seizures are notoriously drug-resistant to multiple antiepileptic medications 4, 5
• Patients require broad-spectrum antiepileptic drugs 4
• This population is most prone to seizure exacerbation by certain AEDs (e.g., carbamazepine can worsen seizures) 4
• Topiramate (6 mg/kg/day) and lamotrigine (doses adjusted for weight and valproate use, 50-400 mg/day) are effective for reducing drop attacks (Level A evidence) 4

Long-term Impact:

Among handicapped children, LGS presents the most serious problems in daily care at home or in institutions due to frequent attacks and marked developmental delays 2. The condition requires lifelong care with significant comorbidities including cognitive impairment, motor dysfunction, psychiatric disturbances, and epilepsy-related complications 7.

The Continuum Concept

These syndromes may represent age-dependent manifestations of the same underlying epileptic encephalopathy, related to the degree of brain immaturity 3, 8. The three most severe childhood epilepsies—Ohtahara syndrome (neonatal), West syndrome (infantile), and Lennox-Gastaut syndrome (early childhood)—display considerable similarities and transitional features, suggesting they form a continuum of epileptic encephalopathies with predictable age-related evolution 8.

Common Pitfalls:

• Diagnostic accuracy is challenging: 46% of clinicians believe LGS is both over- and underdiagnosed, with adult diagnosis being particularly difficult 9
• Treatment inadequacy: 67% of clinicians rate available treatments as inadequate, with barriers including limited medication efficacy (68%), adverse effects (38%), and comorbidity management challenges (37%) 9
• Underutilization of surgical options: Corpus callosotomy is perceived as underutilized (71%), suggesting access disparities 9