Question

Given below are two statements.

Statement I: Auriculopalpebral nerve block is used to cause motor paralysis of eyelids.

Statement II: Pain sensations for eyelids are lost after auriculopalpebral nerve block.

In light of the above statements, choose the correct answer from the options given below.

• A. Both Statement I and Statement II are true.
• B. Both Statement I and Statement II are false.
• C. Statement I is true but Statement II is false.
• D. Statement I is false but Statement II is true.

Hint:

Remember: Auriculopalpebral block = motor block, not sensory block.
It prevents blinking by blocking the motor supply to the orbicularis oculi muscle.
For ophthalmic analgesia, a separate sensory or topical anaesthetic technique is required.
A useful exam association is: auriculopalpebral = eyelid movement; trigeminal branches = eyelid and ocular sensation.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The auriculopalpebral nerve is a motor branch of the facial nerve, cranial nerve VII.
It supplies the muscles responsible for closure of the eyelids, particularly the orbicularis oculi muscle.
Therefore, blocking this nerve produces motor paralysis of the eyelids and prevents normal blinking.
However, the auriculopalpebral nerve does not provide the sensory innervation responsible for pain sensation from the eyelids or the ocular surface.
Key Approach:
The important distinction is between motor innervation and sensory innervation.
The auriculopalpebral nerve is primarily a motor nerve for the eyelids.
Therefore, its blockade causes paralysis of eyelid movement but does not produce complete sensory analgesia of the eyelids.

Step 2: Detailed Explanation:
Statement I: True.
The auriculopalpebral nerve supplies the motor component to the orbicularis oculi muscle.
When the nerve is blocked, contraction of the orbicularis oculi is prevented.
As a result, the animal cannot blink normally and the eyelids remain open.
This property makes the auriculopalpebral nerve block useful during ophthalmic examination and procedures in large animals.
Statement II: False.
The auriculopalpebral nerve block does not produce sensory analgesia of the eyelids.
Pain sensation is carried mainly through sensory branches of the trigeminal nerve, particularly branches associated with the ophthalmic division.
Therefore, if sensory desensitization of the eye or eyelids is required, an appropriate sensory nerve block or topical local anaesthetic must also be used.

Step 3: Final Answer:
Statement I is true because the auriculopalpebral nerve block produces motor paralysis of the eyelids.
Statement II is false because the block does not abolish pain sensation from the eyelids.
Hence, the correct answer is (C) Statement I is true but Statement II is false.