A 6-month-old boy born to consanguineous parents presents with clusters of brief symmetric axial flexor spasms occurring predominantly on awakening over the past 2 weeks. Developmental milestones have regressed. Skin examination reveals hypomelanotic macules and facial angiofibromas. Brain MRI shows multiple cortical tubers and subependymal nodules. The interictal EEG pattern marked **B** in the diagram is obtained. Which of the following is the most appropriate first-line antiepileptic agent for this patient?

Question

Accepted Answer

D. Vigabatrin with regular ophthalmologic monitoring for visual field defects. ## Why Vigabatrin is right

The pattern marked **B** — hypsarrhythmia (high-amplitude chaotic spikes and disorganized background) — is the pathognomonic interictal EEG finding of infantile spasms (West syndrome). In this patient, the clinical presentation (symmetric axial flexor spasms in clusters, developmental regression, age 6 months) combined with MRI findings of cortical tubers and subependymal nodules confirms **tuberous sclerosis complex (TSC)-related infantile spasms**. According to Nelson Pediatrics 22e and ILAE 2023 guidelines, vigabatrin is the **first-line agent specifically for TSC-associated infantile spasms**, with a response rate of 95% (compared to 54% in non-TSC infantile spasms). Vigabatrin inhibits GABA transaminase and is uniquely effective for tuber-driven seizures. However, irreversible peripheral visual field constriction is a serious adverse effect, mandating serial ophthalmologic examinations throughout treatment.

## Why each distractor is wrong

- **Prednisolone (oral corticosteroid)**: While ACTH or oral prednisolone is first-line for **idiopathic** infantile spasms (non-TSC), it is NOT the preferred agent in TSC-related spasms. Vigabatrin is superior in TSC due to its mechanism targeting tuber-driven epileptogenesis.
- **Levetiracetam**: Although a modern broad-spectrum anticonvulsant, levetiracetam is not first-line for infantile spasms in either TSC or non-TSC populations. It lacks the tuber-specific efficacy of vigabatrin.
- **Phenobarbital**: Phenobarbital is an older agent with limited efficacy in infantile spasms and carries significant risk of sedation and behavioral effects in infants. It is not recommended as first-line therapy for West syndrome.

**High-Yield:** Hypsarrhythmia + TSC = Vigabatrin first-line (95% response); non-TSC infantile spasms = ACTH/prednisolone first-line. Always monitor vigabatrin for irreversible visual field loss.

[cite: Nelson Pediatrics 22e; ILAE 2023 Infantile Spasms Guidelines]

Answer

A. Prednisolone (oral corticosteroid) as per standard West syndrome protocol

Answer

B. Levetiracetam with gradual dose escalation

Answer

C. Phenobarbital with therapeutic drug monitoring

Explanation

Why Vigabatrin is right

Why each distractor is wrong

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