Question

A 45-year-old male presents with breathlessness and undergoes a CT scan of the paranasal sinuses (PNS). Which sinus is obstructed?

• A. Maxillary
• B. Frontal
• C. Sphenoid
• D. Ethmoid

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.

Answer 1

The Correct Option is A

Step 1: Read the CT of the paranasal sinuses (coronal section). On a coronal CT-PNS, the normal air-filled sinuses appear BLACK (air). A sinus that is OBSTRUCTED/diseased becomes opacified - it fills with mucus/soft tissue and turns GREY/WHITE, with loss of its normal air shadow and often an air-fluid level.
Step 2: Locate the maxillary sinuses. The maxillary (antral) sinuses are the large paired pyramidal air spaces sitting on either side, below the orbits and lateral to the nasal cavity - the most prominent sinuses on a coronal section. The CT shows opacification (whitening / soft-tissue filling) of the maxillary antrum, indicating its drainage (the ostium into the middle meatus / osteomeatal complex) is obstructed.
Step 3: Why option A is correct. The opacified, fluid/soft-tissue-filled large lateral sinus on the CT is the maxillary sinus; its blocked ostium prevents drainage, so it appears obstructed - matching option A.
Step 4: Why the others are wrong. (B) Frontal sinuses lie ABOVE the orbits in the frontal bone and are not the opacified space shown. (C) Sphenoid sinus is a single midline air space behind the ethmoids/posterior to the nasal cavity (best seen on more posterior cuts), not the large lateral sinus shown. (D) Ethmoid air cells are the small honeycomb cells between the orbits and the nose; they are not the large opacified antrum demonstrated.
Final answer: A. Maxillary.