Question:medium
A 45-year-old male presents with breathlessness and undergoes a CT scan of the paranasal sinuses (PNS). Which sinus is obstructed?
A 45-year-old male presents with breathlessness and undergoes a CT scan of the paranasal sinuses (PNS). Which sinus is obstructed?
Show Hint
On CT-PNS, air is black and a blocked sinus opacifies (turns white). The large pyramidal sinus under each orbit is the maxillary - look for which one is whited out.
Updated On: Jun 22, 2026
- Maxillary
- Frontal
- Sphenoid
- Ethmoid
Show Solution
The Correct Option is A
Solution and Explanation
Use the basic rule of sinus CT first: air is black, and a blocked (obstructed) sinus that fills with mucus or soft tissue turns grey/white and loses its normal black air shadow, sometimes showing an air-fluid level.
Now identify the sinuses by position on a coronal cut:
- Maxillary sinuses = the big paired pyramidal spaces low down, just under the orbits and beside the nose - the largest sinuses you see on the standard coronal image.
- Frontal sinuses = up in the forehead, above the orbits.
- Ethmoid air cells = the little honeycomb cells sandwiched between the two eyes.
- Sphenoid = a single central air space sitting far back, behind the ethmoids.
Match to the picture. The film shows the large lateral antral space whitened out (filled with material) instead of being black with air - that is the maxillary sinus, and its drainage pathway through the osteomeatal complex is blocked, so it is the obstructed one.
Exclusion check: the frontal (above orbit), ethmoid (small inter-orbital cells) and sphenoid (deep midline, posterior) sinuses are in different locations and are not the big opacified cavity displayed.
Answer: A (Maxillary).
Now identify the sinuses by position on a coronal cut:
- Maxillary sinuses = the big paired pyramidal spaces low down, just under the orbits and beside the nose - the largest sinuses you see on the standard coronal image.
- Frontal sinuses = up in the forehead, above the orbits.
- Ethmoid air cells = the little honeycomb cells sandwiched between the two eyes.
- Sphenoid = a single central air space sitting far back, behind the ethmoids.
Match to the picture. The film shows the large lateral antral space whitened out (filled with material) instead of being black with air - that is the maxillary sinus, and its drainage pathway through the osteomeatal complex is blocked, so it is the obstructed one.
Exclusion check: the frontal (above orbit), ethmoid (small inter-orbital cells) and sphenoid (deep midline, posterior) sinuses are in different locations and are not the big opacified cavity displayed.
Answer: A (Maxillary).
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