What are the differences between Dravet syndrome and Lennox‑Gastaut syndrome?

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Dravet Syndrome vs. Lennox-Gastaut Syndrome: Key Clinical Distinctions

Dravet syndrome and Lennox-Gastaut syndrome are distinct developmental and epileptic encephalopathies that differ fundamentally in age of onset, seizure triggers, genetic etiology, and EEG patterns, though both result in drug-resistant epilepsy and cognitive decline.

Age of Onset and Initial Presentation

Dravet syndrome begins in infancy (typically first year of life) in previously normal infants, with febrile or afebrile seizures that often progress to status epilepticus 1. The hallmark is that these initial seizures occur in infants with completely normal development prior to seizure onset 1.

Lennox-Gastaut syndrome begins later in childhood, typically between 1 and 8 years of age 2. Many cases evolve from other epilepsy syndromes or have identifiable structural brain abnormalities from the outset 2.

Seizure Types and Characteristics

Dravet Syndrome

  • Fever sensitivity is the defining clinical feature, with seizures consistently triggered by elevated body temperature 1
  • Initial seizures are typically generalized or unilateral clonic seizures, often prolonged 1
  • Myoclonic seizures and atypical absence seizures develop later in the disease course 1
  • Photosensitivity and pattern-sensitivity are common additional triggers 1

Lennox-Gastaut Syndrome

  • Nocturnal tonic seizures are the most characteristic pattern, though often not present initially 2
  • The triad consists of axial tonic, atonic (drop attacks), and atypical absence seizures 2
  • Myoclonic seizures occur but are less frequent than the primary three types 2
  • No specific seizure triggers like fever or photosensitivity are characteristic 2

EEG Findings

Dravet syndrome does not have a pathognomonic EEG pattern in early stages, though generalized spike-wave discharges develop over time 1.

Lennox-Gastaut syndrome has highly characteristic EEG findings: high-voltage, bifrontal 1.5-2.5 Hz spike-and-wave complexes interictally, and attenuation with paroxysmal fast activity (10-13 Hz) during ictal phases 2. This EEG pattern is a diagnostic criterion 3.

Genetic Etiology

Dravet syndrome has a well-defined genetic basis in approximately 85% of cases, with mutations in SCN1A (encoding voltage-gated sodium channel Nav1.1) being the primary cause 1. PCDH19 mutations account for an additional 5% of cases, particularly in females 1.

Lennox-Gastaut syndrome is predominantly symptomatic/structural rather than genetic, arising from prenatal/perinatal insults including intrauterine infections, vascular injuries, migrational abnormalities, CNS infections, tuberous sclerosis, or metabolic disorders 2. Some cases remain cryptogenic 2.

Diagnostic Challenges and Overlap

A critical clinical pitfall is distinguishing Dravet syndrome from Lennox-Gastaut syndrome early in the disease course, as seizure patterns may overlap initially 2. The key differentiating features are:

  • Fever sensitivity strongly suggests Dravet syndrome 1
  • Age at onset: infancy (<1 year) favors Dravet; 1-8 years favors Lennox-Gastaut 2, 1
  • Normal development before seizure onset favors Dravet syndrome 1
  • Characteristic EEG pattern (slow spike-wave) confirms Lennox-Gastaut 2

Treatment Implications

Both syndromes are profoundly drug-resistant, but treatment approaches differ 2, 4:

For Dravet syndrome:

  • Avoid sodium channel blockers (carbamazepine, phenytoin, lamotrigine) as they may worsen seizures due to the SCN1A pathophysiology 1
  • Stiripentol is specifically indicated for Dravet syndrome 3
  • Cannabidiol (Epidiolex) is FDA-approved specifically for Dravet syndrome 3

For Lennox-Gastaut syndrome:

  • Felbamate, lamotrigine, topiramate, and rufinamide are approved treatments 2
  • Cannabidiol (Epidiolex) is also FDA-approved for Lennox-Gastaut syndrome 3
  • Corpus callosotomy may be considered for drop attacks 2
  • Surgical planning may benefit from FDG-PET in cases with unilateral focal hypometabolism 3

Prognosis and Long-term Outcomes

Both syndromes have poor long-term prognosis with persistent drug-resistant seizures and cognitive decline 2, 1. Most patients with either syndrome develop moderate intellectual disability within years of onset 2. Behavioral problems including inattention, hyperactivity, and aggression are common in both conditions 2. Dravet syndrome is associated with increased mortality rates compared to the general population 4.

References

1
Research

Dravet syndrome: a genetic epileptic disorder.

Acta medica Okayama, 2012

3
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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