**Core Concept**
Bell's palsy is an idiopathic peripheral seventh cranial nerve (facial nerve) dysfunction, presenting as unilateral lower motor neuron facial weakness. The underlying pathophysiology involves inflammation and demyelination of the facial nerve.

**Why the Correct Answer is Right**
The evidence-based therapy for Bell's palsy primarily involves corticosteroids to reduce inflammation and swelling of the facial nerve. Corticosteroids, such as prednisolone, have been shown to improve outcomes and reduce the risk of persistent facial weakness when started within 72 hours of symptom onset. The mechanism of action involves inhibition of phospholipase A2, an enzyme involved in the inflammatory response.

**Why Each Wrong Option is Incorrect**
* **Option A:** Steroids are not the primary treatment for Bell's palsy. **Antiviral medications**, such as acyclovir, have been studied but are not recommended as first-line treatment due to lack of evidence.
* **Option B:** **Antibiotics** are not effective in treating Bell's palsy, as the condition is not caused by a bacterial infection.
* **Option C:** **Surgical decompression** of the facial nerve is not a recommended treatment for Bell's palsy, as the condition is typically self-limiting and resolves with supportive care.

**Clinical Pearl / High-Yield Fact**
Early initiation of corticosteroids within 72 hours of symptom onset is crucial in improving outcomes for patients with Bell's palsy.

**Correct Answer: C. Steroids are the primary evidence-based therapy for Bell's palsy.**