## **Core Concept**
Tetanus is a bacterial infection caused by *Clostridium tetani*, characterized by muscle stiffness and spasms. The primary pathophysiological mechanism involves the toxin-mediated blockade of neurotransmitter release, specifically glycine and GABA, leading to muscle rigidity. The infection typically enters the body through wounds or cuts.

## **Why the Correct Answer is Right**
The correct answer, **D. Muscle stiffness**, is the most common initial symptom of tetanus. This is due to the toxin's effect on the nervous system, causing an imbalance in neurotransmitter release that results in sustained muscle contraction. Muscle stiffness often begins in the jaw muscles (leading to lockjaw) and can spread to other parts of the body.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While trismus (lockjaw) is a classic symptom of tetanus, it is not the most common initial symptom but rather a specific manifestation of muscle stiffness.
- **Option B:** Dysphagia (difficulty swallowing) can occur due to muscle stiffness but is not the most common initial symptom.
- **Option C:** Generalized seizures are not typical of tetanus; instead, muscle spasms and rigidity are more characteristic.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that tetanus infection does not confer immunity, and thus, individuals can be infected multiple times. A critical preventive measure is vaccination, typically administered in a series during childhood and boosted periodically.

## **Correct Answer:** D. Muscle stiffness