**Core Concept**
Infantile spasms, also known as West syndrome, are a severe and potentially life-threatening form of epilepsy that affects infants. The treatment of infantile spasms involves medications that can help control seizures and promote brain development.

**Why the Correct Answer is Right**
The drug of choice for infantile spasms is adrenocorticotropic hormone (ACTH), which is a synthetic form of a hormone produced by the pituitary gland. ACTH has been shown to be effective in reducing the frequency and severity of seizures in infants with infantile spasms. The mechanism of action of ACTH is not fully understood, but it is thought to involve the promotion of brain development and the reduction of excitatory neurotransmitter release.

**Why Each Wrong Option is Incorrect**
**Option A:** Vigabatrin is an antiepileptic medication, but it is not the first-line treatment for infantile spasms.
**Option B:** Phenobarbital is a common antiepileptic medication, but it is not effective in treating infantile spasms.
**Option C:** Topiramate is another antiepileptic medication, but it is not the preferred treatment for infantile spasms.

**Clinical Pearl / High-Yield Fact**
Infantile spasms are a medical emergency, and prompt treatment is essential to prevent long-term neurological damage. ACTH is usually administered intramuscularly, and its effectiveness can be monitored through regular EEG and clinical assessments.

**Correct Answer: C. ACTH. Adrenocorticotropic hormone.**