What is the first-line treatment for infantile spasms?

First-Line Treatment for Infantile Spasms

Vigabatrin is the first-line treatment of choice for infantile spasms, particularly for newly diagnosed cases. 1

Treatment Options and Evidence

Vigabatrin

• Dosing: Initial daily dosing is 50 mg/kg/day given in two divided doses (25 mg/kg twice daily)
• Titration: Can be increased by 25-50 mg/kg/day every 3 days
• Maximum dose: Up to 150 mg/kg/day given in 2 divided doses (75 mg/kg twice daily) 2
• Response time: Typically within 1-14 days, with two-thirds of responders showing improvement within 3 days 3

ACTH (Adrenocorticotropic Hormone)

• Alternative first-line option, particularly effective for certain etiologies
• Used when vigabatrin fails or is contraindicated
• Higher response rate in some studies (74% vs 48% for vigabatrin) 3
• More side effects compared to vigabatrin (37% vs 13%) 3

Efficacy Based on Etiology

Different etiologies respond differently to treatment:

1. Tuberous sclerosis: Vigabatrin shows superior efficacy 3
2. Cerebral malformations: Vigabatrin preferred 3
3. Perinatal hypoxic/ischemic injury: ACTH tends to be more effective 3
4. Cryptogenic cases: Similar efficacy between vigabatrin and ACTH 3

Treatment Duration and Monitoring

• Duration: Limited data suggest vigabatrin could be withdrawn without relapse in infants who have been spasm-free for six months 1
• Monitoring: Regular assessment of seizure control and development
• Vision monitoring: Due to risk of permanent vision loss, vision assessment is recommended at baseline (no later than 4 weeks after starting vigabatrin), at least every 3 months during therapy, and about 3-6 months after discontinuation 2

Treatment Algorithm

1. First-line: Start with vigabatrin at 50 mg/kg/day in two divided doses
2. If no response within 2 weeks: Consider switching to ACTH
3. If partial response: Titrate vigabatrin up to maximum of 150 mg/kg/day
4. If still inadequate control: Add or switch to ACTH
5. If spasms controlled: Continue treatment and consider withdrawal after 6 months of spasm freedom

Important Considerations

Vision Risk with Vigabatrin

• Vigabatrin can cause permanent bilateral concentric visual field constriction
• Risk increases with higher doses and longer exposure
• Regular vision assessment is crucial, though challenging in infants 2

Treatment Failure

• If no substantial clinical benefit is observed within 2-4 weeks of initiating vigabatrin for infantile spasms, treatment should be discontinued 2
• Consider alternative therapy (typically ACTH) if treatment failure becomes obvious

Relapse Risk

Studies show that relapse rates may differ between treatments:

• Vigabatrin: Lower relapse rate in some studies (1/18 patients vs 6/25 for ACTH) 3
• Long-term outcomes appear similar between vigabatrin and ACTH treatment groups 4

Conclusion

While both vigabatrin and ACTH are effective treatments for infantile spasms, vigabatrin is generally recommended as the first-line therapy due to its favorable side effect profile, particularly for certain etiologies like tuberous sclerosis. The choice between these medications should consider the underlying etiology of the infantile spasms, with ACTH being preferred in cases of hypoxic-ischemic injury, and vigabatrin being preferred in tuberous sclerosis and cerebral malformations.