59-year-old man has difficulty in breathing through his nose. On examination, his physician finds that he has swelling of mucous membranes of the superior nasal meatus. Which opening of the paranasal sinuses is most likely plugged?
**Core Concept**
The superior nasal meatus is a narrow passage in the nasal cavity that serves as a drainage pathway for the posterior ethmoidal air cells and the sphenoid sinus. Swelling of the mucous membranes in this region suggests an obstruction of the drainage pathway, which could be caused by inflammation or infection.
**Why the Correct Answer is Right**
The superior nasal meatus is closely associated with the sphenoid sinus. The sphenoid sinus opens into the superior nasal meatus through a small ostium. Swelling of the mucous membranes in this area may indicate an obstruction of the sphenoid sinus ostium, leading to impaired drainage and subsequent inflammation.
**Why Each Wrong Option is Incorrect**
* **Option A:** The anterior ethmoidal air cells drain into the middle nasal meatus, not the superior nasal meatus. Therefore, swelling in the superior nasal meatus is less likely to be related to the anterior ethmoidal air cells.
* **Option B:** The frontal sinus and the maxillary sinus drain into the middle and inferior nasal meatuses, respectively. The swelling in the superior nasal meatus suggests an issue with the posterior ethmoidal air cells or the sphenoid sinus, making this option incorrect.
* **Option D:** The nasolacrimal duct opens into the inferior nasal meatus and is not directly related to the superior nasal meatus or the sphenoid sinus.
**Clinical Pearl / High-Yield Fact**
When evaluating nasal congestion or difficulty breathing through the nose, it's essential to consider the specific nasal meatus involved, as this can help narrow down the possible causes and guide further diagnostic testing.
**Correct Answer:** C.