A person wakes up with pain, paraesthesia, tingling in the arms. He had slept with arm below the head. Which fibers are involved?
**Core Concept**
The scenario describes a case of compression neuropathy due to prolonged pressure on the brachial plexus, specifically the ulnar nerve. This condition is known as **Saturday night palsy** or **waiter's tip palsy**. The brachial plexus is a complex network of nerves that arise from the spinal cord and supply the arm.
**Why the Correct Answer is Right**
The symptoms described, such as pain, paraesthesia, and tingling in the arms, are characteristic of nerve compression. In this case, the ulnar nerve is likely affected. The ulnar nerve originates from the C8 and T1 nerve roots and passes through the brachial plexus. When the arm is bent at the elbow and rests on a hard surface, the ulnar nerve can become compressed. This compression can lead to numbness, tingling, and weakness in the hand, particularly affecting the little finger and ring finger.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the scenario described. The median nerve is involved in conditions such as carpal tunnel syndrome, which affects the thumb and index finger.
* **Option B:** The radial nerve is responsible for wrist extension and is not typically involved in Saturday night palsy.
* **Option C:** The axillary nerve is involved in shoulder movement and is not typically affected in this scenario.
**Clinical Pearl / High-Yield Fact**
Remember that prolonged pressure on the ulnar nerve can cause numbness and tingling in the hand, particularly affecting the little finger and ring finger. This is a classic example of a compressive neuropathy.
**Correct Answer:** C.