Question

Pain sensation from the ethmoid sinus is carried by:

• A. Frontal nerve
• B. Lacrimal nerve
• C. Nasociliary nerve
• D. Infraorbital nerve

Hint:

Trace the anterior and posterior ethmoidal nerves back to their parent branch of V1.

Answer 1

The Correct Option is C

Step 1: Recall the innervation of the ethmoid sinuses.
The ethmoidal air cells are supplied by the anterior and posterior ethmoidal nerves. These are branches of the nasociliary nerve, which itself arises from the ophthalmic division (V1) of the trigeminal nerve.

Step 2: Trace the pathway.
The nasociliary nerve gives off the anterior ethmoidal nerve (supplying the anterior and middle ethmoidal cells) and the posterior ethmoidal nerve (supplying the posterior ethmoidal cells and sphenoid sinus). Pain from the ethmoid sinus thus travels via these ethmoidal nerves back to the nasociliary nerve.

Step 3: Eliminate the others.
The frontal nerve supplies the forehead, scalp and frontal sinus area.
The lacrimal nerve supplies the lacrimal gland and lateral upper eyelid.
The infraorbital nerve (from V2) supplies the maxillary sinus, lower eyelid, cheek and upper lip.

Step 4: Conclusion.
Pain from the ethmoid sinus is carried by the nasociliary nerve (option C). This matches the printed key.