**Core Concept**
Essential tremor is a chronic neurological disorder characterized by involuntary tremors, particularly in the hands, often exacerbated by stress and fatigue. The pathophysiology involves an imbalance between excitatory and inhibitory neurotransmitters in the brain, particularly in the cerebellum and its connections.

**Why the Correct Answer is Right**
The first-line treatment for essential tremor often involves medications that enhance the activity of inhibitory neurotransmitters, such as gamma-aminobutyric acid (GABA). Propranolol, a non-selective beta-blocker, is commonly used as a first-line treatment due to its ability to reduce tremor severity by inhibiting the beta-adrenergic receptors in the brain. This action decreases the excitatory effects of norepinephrine on the cerebellum, leading to a reduction in tremor amplitude. Propranolol has been shown to be effective in reducing tremor severity in patients with essential tremor.

**Why Each Wrong Option is Incorrect**
**Option A:** Primidone is an anticonvulsant medication that is also used to treat essential tremor. However, it is typically considered a second-line treatment due to its potential side effects and the need for regular blood monitoring to assess liver function.

**Option B:** Topiramate is an anticonvulsant medication that has been used off-label to treat essential tremor. While it may be effective, it is not typically considered a first-line treatment due to its side effect profile and the availability of more established options like propranolol.

**Option C:** Botulinum toxin injections are a treatment option for essential tremor, particularly for patients with severe tremors or those who do not respond to medication. However, it is typically considered a second-line treatment due to the need for repeated injections and potential side effects.

**Option D:** There is no medication listed as option D.

**Clinical Pearl / High-Yield Fact**
When treating essential tremor, it's essential to consider the patient's overall health and potential interactions between medications. For example, beta-blockers like propranolol can exacerbate obstructive airway diseases, so patients with asthma or COPD may require alternative treatment options.

**Correct Answer:** C.