In Hansen’s disease, the nerve commonly affected at elbow is: September 2005
**Core Concept**
Hansen's disease, also known as leprosy, is a chronic bacterial infection caused by Mycobacterium leprae that primarily affects the peripheral nerves, skin, and mucous membranes. The disease leads to demyelination and axonal degeneration in affected nerves, resulting in sensory, motor, and autonomic dysfunction.
**Why the Correct Answer is Right**
In Hansen's disease, the ulnar nerve is commonly affected at the elbow. This is due to the nerve's anatomical susceptibility to compression and damage at the cubital tunnel, which is a narrow space at the elbow through which the ulnar nerve passes. The compression of the ulnar nerve at this site leads to symptoms such as numbness, tingling, and weakness in the hand and forearm. The ulnar nerve is responsible for innervating the intrinsic muscles of the hand, as well as providing sensation to the medial aspect of the arm and forearm.
**Why Each Wrong Option is Incorrect**
* **Option A:** The radial nerve is not typically affected in Hansen's disease. It is more commonly associated with radial tunnel syndrome, which is a separate entity characterized by compression of the radial nerve at the radial tunnel.
* **Option B:** The median nerve is not typically affected at the elbow in Hansen's disease. It is more commonly associated with carpal tunnel syndrome, which is a separate entity characterized by compression of the median nerve at the wrist.
* **Option D:** The musculocutaneous nerve is not typically affected in Hansen's disease. It is primarily responsible for innervating the flexor muscles of the elbow and forearm.
**Clinical Pearl / High-Yield Fact**
The ulnar nerve is commonly affected at the elbow in Hansen's disease due to its anatomical susceptibility to compression at the cubital tunnel. This is a classic exam trap that students should be aware of, as it is a common site of nerve compression in this disease.
**Correct Answer: C. Ulnar nerve.**