A 32 year old man visits his physician and is diagnosed with a herniated disc impinging the spinal nerve that exits inferior to the C6 veebra. Pain from the impinged nerve would most likely radiate to which cutaneous region?
## **Core Concept**
The question tests knowledge of spinal nerve anatomy and dermatomal distribution. Each spinal nerve corresponds to a specific dermatome, which is a cutaneous region innervated by that nerve. The spinal nerves exit the spinal canal through intervertebral foramina, and their exit points are typically inferior to the corresponding vertebral body.
## **Why the Correct Answer is Right**
The C7 spinal nerve exits inferior to the C6 vertebra. Dermatomes are arranged in a segmental fashion along the body, with C5-C8 dermatomes covering the arm. Specifically, the C7 dermatome covers the skin of the posterior arm, forearm, and the middle finger. Therefore, pain radiating from a herniated disc impinging the C7 spinal nerve (which exits below C6) would most likely be felt in the C7 dermatome.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not correspond to the dermatome associated with the C7 spinal nerve.
- **Option B:** This option is incorrect because it does not accurately represent the dermatomal distribution relevant to the C7 nerve.
- **Option D:** This option is incorrect because it represents a different dermatome, not the one associated with the C7 spinal nerve.
## **Clinical Pearl / High-Yield Fact**
A useful clinical correlation to remember is that the dermatomes of the upper limb are arranged as follows: C5 (lateral arm), C6 (lateral forearm and thumb), C7 (middle finger and posterior arm and forearm), C8 (medial forearm and little finger). This pattern helps in localizing the level of nerve impingement based on the distribution of pain or sensory changes.
## **Correct Answer:** . C7 dermatome