Chassaignac’s tubercle lies at the level of –
**Core Concept**
Chassaignac's tubercle is a bony projection located on the anterior aspect of the scalene muscles at the level of the sixth cervical vertebra (C6). This anatomical landmark is significant in the context of brachial plexus anatomy and surgical procedures, such as nerve blocks.
**Why the Correct Answer is Right**
The correct answer is related to the anatomical location of Chassaignac's tubercle, which corresponds to the level of the sixth cervical vertebra (C6). This is a key reference point for identifying the location of the brachial plexus and its associated structures, particularly during regional anesthesia procedures. The scalene muscles, which are located anterior to Chassaignac's tubercle, play a crucial role in the formation of the brachial plexus.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Chassaignac's tubercle is not located at the level of the first cervical vertebra (C1). The first cervical vertebra is located at the base of the skull and is not associated with the brachial plexus.
**Option B:** This option is incorrect because Chassaignac's tubercle is not located at the level of the fifth cervical vertebra (C5). While C5 is a key component of the brachial plexus, Chassaignac's tubercle is specifically located at the level of C6.
**Option D:** This option is incorrect because Chassaignac's tubercle is not located at the level of the seventh cervical vertebra (C7). C7 is also a component of the brachial plexus, but Chassaignac's tubercle is specifically located at the level of C6.
**Clinical Pearl / High-Yield Fact**
Chassaignac's tubercle is a critical landmark in the context of regional anesthesia, particularly for nerve blocks involving the brachial plexus. Identifying the correct level of Chassaignac's tubercle is essential for accurate placement of the needle and minimizing the risk of complications.
**Correct Answer:** C. C6.