Paralysis is the loss of function in a part of your body. Arm paralysis and hand paralysis occur when something interrupts the messages passed between your brain and your arm or hand muscles, preventing you from voluntarily moving your upper extremities.
The muscles in your hands and arms are controlled by the median, ulnar, and radial nerves, plus the brachial plexus nerve network.
- The median nerve originates at your shoulder and controls your precision hand movements, such as pinching motions. It controls sensation in all fingers but the ring finger and little finger. The median nerve enters the hand through the carpal tunnel (formed by the wrist's carpal bones).
- The ulnar nerve runs through your arm into the hand and connects to the little finger and adjacent side of the ring finger, allowing you to grasp objects and feel sensation on the palm side of your hand. When you bump your "funny bone" and feel a painful shock, the ulnar nerve, the largest unprotected nerve in the body, brings you the painful sensation.
- The radial nerve is in charge of your ability to extend your wrist and move the position of your hand. It provides sensation from the back of the little finger and the nearest half of the ring finger.
- Brachial plexus nerves are a network (plexus) of nerves that send information from your spinal cord down to your shoulders, arms, and hands.