## **Core Concept**
Sinusitis in children often involves the paranasal sinuses, which are air-filled cavities surrounding the nasal cavity. The ethmoidal sinuses are particularly relevant in pediatric patients due to their anatomy and developmental stage.

## **Why the Correct Answer is Right**
The ethmoidal sinuses (**Option C**) are the most common site of sinusitis in children. This is because the ethmoidal sinuses are present at birth and continue to develop throughout childhood. Their complex anatomy with multiple small cells makes them prone to infection and inflammation. The ethmoidal sinuses are also closely related to the nasal cavity, making it easier for pathogens to spread and cause infection.

## **Why Each Wrong Option is Incorrect**
* **Option A:** While the maxillary sinuses can be involved in sinusitis, they are not the most common site in children. Maxillary sinusitis is more commonly seen in adults.
* **Option B:** The sphenoidal sinuses are less commonly involved in sinusitis, especially in children, due to their late development and deeper location.
* **Option D:** The frontal sinuses are typically not fully developed until late adolescence, making them an uncommon site for sinusitis in children.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the ethmoidal sinuses are often involved in pediatric sinusitis due to their underdeveloped drainage system and complex anatomy. Clinical suspicion and imaging studies, such as X-rays or CT scans, are crucial for diagnosing sinusitis in children.

## **Correct Answer:** . Ethmoidal sinuses