## **Core Concept**
The question pertains to a complication following total thyroidectomy, specifically the development of respiratory stridor. This condition often arises due to injury or edema of structures in the neck that are crucial for airway patency.

## **Why the Correct Answer is Right**
The correct answer, **B. Bilateral recurrent laryngeal nerve palsy**, is right because the recurrent laryngeal nerves are vital for controlling the muscles of the larynx, particularly the posterior cricoarytenoid muscles, which are the only muscles responsible for opening (abducting) the glottis. Injury to these nerves during thyroid surgery can lead to bilateral vocal cord paralysis in a paramedian position, resulting in inspiratory stridor due to the narrowed airway.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Unilateral recurrent laryngeal nerve palsy would typically cause hoarseness of voice but not necessarily stridor, as one side of the larynx still functions normally, maintaining a somewhat patent airway.
- **Option C:** The superior laryngeal nerve primarily affects the sensation of the larynx above the vocal cords and the cricothyroid muscle, which is involved in voice pitch. Damage to this nerve would not typically cause stridor.
- **Option D:** While hematoma formation can cause airway obstruction leading to stridor, it is not specifically related to the function of nerves and is a more immediate and severe complication that would likely present with more acute symptoms.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that bilateral recurrent laryngeal nerve palsy can lead to a life-threatening airway emergency. Stridor following thyroid surgery is an indication for immediate evaluation and possible intervention, such as reintubation or tracheotomy.

## **Correct Answer: B. Bilateral recurrent laryngeal nerve palsy**