**Question:** Pain sensation from ethmoid sinus is transmitted through

A. Cranial nerve V
B. Cranial nerve II
C. Cranial nerve V2
D. Cranial nerve V1

**Correct Answer:** C. Cranial nerve V2

**Core Concept:**
The ethmoid sinus is a part of the paranasal sinus complex, located within the skull base and connected to the nasal cavity. Pain sensation from this sinus typically arises due to inflammation or infection and is transmitted through the trigeminal nerve, specifically the division V2.

**Why the Correct Answer is Right:**
The correct answer is Cranial nerve V2 because it is responsible for sensory innervation of the posterior third of the nasal mucosa and the inferior aspect of the nasal septum, which includes the region of the ethmoid sinus.

**Why Each Wrong Option is Incorrect:**
A. Cranial nerve V (V1 and V3) is primarily responsible for sensory innervation of the anterior and lateral aspects of the nose and anterior two-thirds of the nasal septum, not the posterior ethmoid area.
B. Cranial nerve II (ophthalmic nerve) is responsible for sensory innervation of the eye, eyelids, and forehead, not the nasal region.
D. Cranial nerve V1 is involved in sensory innervation of the upper lip, nose, and cheek, not the posterior ethmoid area.

**Clinical Pearl:**
Understanding the correct sensory innervation of various regions of the body is crucial for correctly identifying the source of pain and selecting appropriate diagnostic and therapeutic interventions. In clinical practice, knowledge of the anatomy of the cranial nerves is essential for accurate diagnosis and management of conditions affecting the head and neck.