Median nerve injury at the wrist is commonly tested by-
**Core Concept**
Median nerve injury at the wrist affects the **thenar muscles** and **lateral two lumbricals**, leading to impaired thumb opposition and flexion. The **median nerve** is responsible for innervating these muscles, as well as providing sensation to the **palmar surface of the thumb, index, and middle fingers**.
**Why the Correct Answer is Right**
The correct answer is related to the function of the median nerve, specifically the **opposition of the thumb**, which is crucial for grasping and fine motor activities. The median nerve injury at the wrist would result in **thenar atrophy** and **weakness in thumb opposition**, making it difficult to perform activities that require gripping or holding objects.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to the function of the median nerve at the wrist.
**Option B:** This option is incorrect because it is not a common test for median nerve injury at the wrist.
**Option C:** This option is incorrect because it is not directly related to the median nerve function.
**Option D:** This option is incorrect because it is not a common test for median nerve injury at the wrist.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **median nerve injury at the wrist** can result in **ape-hand deformity**, characterized by **thenar atrophy** and **inability to oppose the thumb**. This deformity is a classic sign of median nerve damage.
**Correct Answer:** D. Testing opposition of the thumb.