A 5-month-old girl presents with clusters of epileptic spasms on awakening. Examination reveals multiple ash-leaf spots and a shagreen patch. Cardiac echo shows rhabdomyomas, and renal ultrasound shows bilateral angiomyolipomas. MRI brain demonstrates cortical tubers, subependymal nodules, and a small SEGA. The EEG pattern marked **A** in the diagram shows a modified hypsarrhythmia with multifocal spikes and preserved interhemispheric synchrony, more prominent over one hemisphere. Genetic testing confirms TSC2 mutation. What is the first-line antiepileptic drug for this patient's infantile spasms?

Question

Accepted Answer

C. Vigabatrin 100–150 mg/kg/day (irreversible GABA-transaminase inhibitor). ## Why Vigabatrin is correct

The EEG pattern marked **A** — modified hypsarrhythmia with multifocal spikes in the setting of tuberous sclerosis — is the diagnostic hallmark of TSC-related infantile spasms. Unlike idiopathic West syndrome (classic hypsarrhythmia, marked **B**), which responds to ACTH, infantile spasms in TSC are VIGABATRIN-responsive. Vigabatrin achieves seizure freedom in 95% of TSC-related infantile spasms through irreversible inhibition of GABA-transaminase, increasing GABA availability. This patient's clinical presentation (ash-leaf spots, cardiac rhabdomyomas, cortical tubers, SEGA, TSC2 mutation) confirms TSC, making vigabatrin the unequivocal first-line therapy at 100–150 mg/kg/day. Early vigabatrin treatment improves long-term cognitive outcomes in TSC.

## Why each distractor is wrong

- **ACTH**: First-line for idiopathic West syndrome (classic hypsarrhythmia, marked **B**), NOT for TSC-related infantile spasms. ACTH is ineffective in TSC and delays optimal therapy.
- **Levetiracetam**: Useful for refractory seizures in TSC but not first-line for infantile spasms. It lacks the rapid efficacy of vigabatrin in this context.
- **Topiramate**: A broad-spectrum AED used in TSC-related seizures but inferior to vigabatrin for infantile spasms; not first-line for this age and presentation.

**High-Yield:** In TSC with infantile spasms, vigabatrin (not ACTH) is first-line; modified hypsarrhythmia on EEG is the diagnostic clue. Monitor for peripheral visual field constriction (30–40% risk).

[cite: Nelson Textbook of Pediatrics, 21st ed., Chapter 614: Tuberous Sclerosis Complex]

Answer

A. ACTH 0.03–0.05 units/kg/day (adrenocorticotropic hormone)

Answer

B. Topiramate 5–9 mg/kg/day (carbonic anhydrase inhibitor and GABA modulator)

Answer

D. Levetiracetam 10–20 mg/kg/day (synaptic vesicle protein 2A antagonist)

Explanation

Why Vigabatrin is correct

Why each distractor is wrong

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