Dravet Syndrome: Diagnostic Workup and Treatment
Immediate Diagnostic Approach
For any infant aged 2-15 months presenting with a first prolonged hemiclonic seizure or convulsive status epilepticus triggered by fever or vaccination (without another identifiable cause), immediately order genetic testing for SCN1A mutation to diagnose Dravet syndrome 1. This represents the strongest consensus from international experts and should not be delayed.
Key Clinical Red Flags Requiring Genetic Testing
- Prolonged febrile or non-febrile seizures before 1 year of age 2
- Multiple seizure types before 1 year of age 2
- Seizures sensitive to temperature changes before 1 year of age 2
- Neurodevelopmental regression or stagnation 2
Diagnostic Timeline Reality
The median time from seizure onset to formal diagnosis is currently 11 months, with 25% of patients not diagnosed until after 23 months of age 3. Do not wait for "confirmatory" clinical evolution—genetic testing should be ordered at first consultation when clinical suspicion exists 3.
Essential Baseline Workup
- EEG: Document seizure types and baseline patterns (though often initially normal)
- Brain MRI: Rule out structural abnormalities (typically normal in DS)
- Genetic testing: SCN1A sequencing as first-line; consider epilepsy gene panel if SCN1A negative but clinical suspicion remains high 1, 4
- Baseline labs: CBC, comprehensive metabolic panel, liver function tests (critical before initiating valproate)
First-Line Treatment Regimen
Initiate valproate (VPA) as the foundational antiseizure medication immediately upon diagnosis or strong clinical suspicion 5, 6, 4. This has the strongest evidence base and expert consensus.
Valproate Dosing
- Start 10-15 mg/kg/day divided twice daily
- Titrate to 20-40 mg/kg/day based on response and tolerability
- Monitor liver function tests and ammonia levels regularly
Add Clobazam (CLB) as Second Agent
Add clobazam early (within weeks to months) as most patients require dual therapy 5, 6.
- Start 0.25-0.5 mg/kg/day
- Titrate to 0.5-1 mg/kg/day (maximum 40 mg/day)
Third-Line DS-Specific Therapies
When VPA + CLB combination is insufficient (which occurs in the majority), add one of three FDA/EMA-approved DS-specific medications 5, 7:
Option 1: Stiripentol (STP)
- Approved for ages ≥6 months 8
- Dose: 50 mg/kg/day divided 2-3 times daily with food
- Critical interaction: Increases CLB and norclobazam levels by inhibiting CYP3A4—expect increased somnolence and may need to reduce CLB dose by 25-50% 5, 8
- Also increases VPA levels; monitor for GI adverse events 5
- High rates of seizure freedom including status epilepticus control 8
Option 2: Cannabidiol (CBD)
- Dose: Start 2.5 mg/kg twice daily, increase weekly to target 10 mg/kg twice daily (maximum 20 mg/kg/day)
- Critical interaction: Bidirectional interaction with CLB—increases norclobazam and 7-OH-CBD, causing somnolence 5
- Monitor liver transaminases closely, especially with concomitant VPA (can cause significant elevations) 5
- May require CLB dose reduction
Option 3: Fenfluramine (FFA)
- Dose: Start 0.2 mg/kg/day, titrate to 0.4-0.7 mg/kg/day (maximum 26 mg/day)
- Requires dose reduction to 0.2-0.4 mg/kg/day if combined with stiripentol 5
- Mandatory cardiac monitoring: Baseline and every 6-month echocardiograms to monitor for valvular heart disease (though none documented at low DS doses) 5
- Monitor for weight loss 5
Alternative Third-Line: Topiramate
- Dose: 3-9 mg/kg/day divided twice daily
- Avoid combining with VPA due to risk of encephalopathy and hyperammonemia 5
- Consider if other DS-specific agents unavailable or not tolerated
Medications to AVOID
Never use sodium channel blockers (carbamazepine, oxcarbazepine, lamotrigine, phenytoin) as they worsen seizures in Dravet syndrome 6, 4.
Rescue Medication Protocol
Every patient must have a benzodiazepine rescue medication at home 7, 4:
- Intranasal midazolam (preferred): 0.2 mg/kg (ages 6 months-5 years), 5 mg (ages 6-11 years), 10 mg (≥12 years)
- Buccal midazolam: 0.5 mg/kg
- Rectal diazepam: 0.5 mg/kg (if other routes unavailable)
- Intramuscular midazolam: For caregivers trained in administration
Administer after 3-5 minutes of continuous seizure activity; call emergency services if seizure continues beyond 5 minutes despite rescue medication 7.
Seizure Trigger Avoidance
Counsel families to strictly avoid/minimize 6, 4:
- Hyperthermia: Aggressive fever management with antipyretics at first sign of illness
- Hot baths: Use lukewarm water only
- Overheating: Avoid excessive bundling, hot environments
- Flashing lights/patterns: Screen time moderation (though less sensitive than other photosensitive epilepsies)
- Sleep deprivation: Maintain consistent sleep schedule
- Overexertion: Balance activity with rest
Vaccination Considerations
Do NOT withhold vaccinations—the risk of vaccine-preventable illness far outweighs theoretical seizure risk 4. However, administer prophylactic antipyretics and consider pre-treatment with rescue benzodiazepine for high-risk patients.
Monitoring Requirements
Laboratory Monitoring
- VPA levels: Target 50-100 mcg/mL (though clinical response more important than level)
- Liver function tests: Baseline, then monthly × 6 months, then every 3-6 months
- CBC: Every 3-6 months (VPA can cause thrombocytopenia)
- Ammonia: If encephalopathy symptoms develop
- Transaminases: More frequently if on CBD + VPA combination
Cardiac Monitoring (if on fenfluramine)
- Echocardiogram at baseline, 3 months, then every 6 months 5
Growth and Development
- Monitor weight (especially with fenfluramine—can cause weight loss)
- Developmental assessments every 6-12 months
- Screen for comorbidities: behavioral problems, sleep disorders, orthopedic issues
Comorbidity Management
Neurodevelopmental Support
- Early intervention services: Physical therapy, occupational therapy, speech therapy starting at diagnosis 4
- Neuropsychological evaluation: At school entry age
- Individualized Education Plan (IEP): Coordinate with school system
Common Comorbidities to Screen For
- Cognitive impairment (universal)
- Behavioral disorders (ADHD, autism spectrum features)
- Sleep disturbances
- Gait abnormalities/ataxia
- Orthopedic issues (crouch gait)
Critical Pitfalls to Avoid
- Delaying genetic testing while waiting for "typical evolution"—test immediately when clinical suspicion exists 3
- Using sodium channel blockers—they worsen seizures 6, 4
- Inadequate rescue medication planning—every family needs home rescue therapy 7
- Ignoring drug-drug interactions when adding DS-specific therapies—particularly STP/CLB and CBD/CLB interactions requiring dose adjustments 5
- Withholding vaccinations—continue routine immunizations with fever precautions 4
- Monotherapy expectations—nearly all patients require polypharmacy; VPA alone is rarely sufficient 5, 6
Treatment Algorithm Summary
- Suspect DS → Order genetic testing immediately (don't wait)
- Start VPA (10-40 mg/kg/day)
- Add CLB within weeks to months (0.5-1 mg/kg/day)
- If inadequate control → Add DS-specific agent:
- Stiripentol (reduce CLB dose by 25-50%)
- OR Cannabidiol (monitor LFTs closely, may reduce CLB)
- OR Fenfluramine (cardiac monitoring required)
- Prescribe rescue benzodiazepine (intranasal/buccal midazolam preferred)
- Counsel on trigger avoidance (fever, heat, sleep deprivation)
- Initiate developmental support services immediately
The goal is ≥50% seizure reduction and elimination of status epilepticus, as complete seizure freedom is rare 4. Early diagnosis and prompt initiation of appropriate therapy may improve long-term neurodevelopmental outcomes 7.