Certified Neuroscience Registered Nurse (CNRN) Practice Exam

What is the most common cause of a radial nerve injury?

1. Humerus fracture

2. Carpal tunnel syndrome

3. Wrist sprain

4. Ulnar nerve entrapment

The correct answer is: Humerus fracture

The most common cause of a radial nerve injury is a humerus fracture. This injury often occurs when individuals experience trauma to the arm, particularly in cases where the mid-shaft of the humerus is fractured. The radial nerve runs in close proximity to the humerus, and fractures in this area can lead to compression or direct damage to the nerve. Understanding the anatomy of the radial nerve is key to recognizing how such injuries can occur. The radial nerve innervates the muscles responsible for extending the wrist and fingers, and it also provides sensation to parts of the forearm and hand. When this nerve is compromised due to a fracture, it can result in characteristic symptoms such as wrist drop, where the patient is unable to extend their wrist and fingers. Other options, while they represent various conditions that can affect the hand and arm, are not as closely associated with injury to the radial nerve. For example, carpal tunnel syndrome primarily affects the median nerve, wrist sprains and ulnar nerve entrapment involve different nerves and locations that do not typically result in the same kind of injury as a humerus fracture would.