Ulnar Nerve Entrapment at the Elbow
Ulnar nerve entrapment occurs when the ulnar nerve in the arm becomes compressed or irritated. The ulnar nerve is one of the three main nerves in your arm. It travels from your neck down into your hand, and can be constricted in several places along the way. Depending upon where it occurs, this pressure on the nerve can cause numbness or pain in your elbow, hand, wrist, or fingers.
Sometimes the ulnar nerve gets compressed at the wrist, beneath the collarbone, or as it comes out of the spinal cord in the neck. The most common place where the nerve gets compressed is behind the elbow.
When the nerve compression occurs at the elbow, it is called “cubital tunnel syndrome.”
At the elbow, the ulnar nerve travels through a tunnel of tissue (the cubital tunnel) that runs under a bump of bone at the inside of your elbow. This bony bump is called the medial epicondyle. The spot where the nerve runs under the medial epicondyle is commonly referred to as the “funny bone.” At the funny bone the nerve is close to your skin, and bumping it causes a shock-like feeling.
Beyond the elbow, the ulnar nerve travels under muscles on the inside of your forearm and into your hand on the side of the palm with the little finger. As the nerve enters the hand, it travels through another tunnel (Guyon’s canal).
The ulnar nerve gives feeling to the little finger and half of the ring finger. It also controls most of the little muscles in the hand that help with fine movements, and some of the bigger muscles in the forearm that help you make a strong grip.
In many cases of cubital tunnel syndrome, the exact cause is not known. The nerve is especially vulnerable to compression at the elbow because it must travel through a narrow space with very little soft tissue to protect it.
Common Causes of Compression
There are several things that can cause pressure on the nerve at the elbow:
When your bend your elbow, the ulnar nerve stretches around the boney ridge of the medial epicondyle. Because this can irritate the nerve, keeping your elbow bent for long periods or repeatedly bending your elbow can cause painful symptoms. For example, many people sleep with their elbows bent. This can aggravate symptoms of ulnar nerve compression and cause you to wake up at night with your fingers asleep.
- In some people, the nerve slides out from behind the medial epicondyle when the elbow is bent. Over time, this sliding back and forth may irritate the nerve.
- Leaning on your elbow for long periods of time can put pressure on the nerve.
- Fluid buildup in the elbow can cause swelling that may compress the nerve.
- A direct blow to the inside of the elbow can cause pain, electric shock sensation, and numbness in the little and ring fingers. This is commonly called “hitting your funny bone.”
Cubital tunnel syndrome can cause an aching pain on the inside of the elbow.
Most of the symptoms, however, occur in your hand.
- Ulnar nerve entrapment can give symptoms of “falling asleep” in the ring finger and little finger, especially when your elbow is bent. In some cases, it may be harder to move your fingers in and out, or to manipulate objects.
- Numbness and tingling in the ring finger and little finger are common symptoms of ulnar nerve entrapment. Often, these symptoms come and go. They happen more often when the elbow is bent, such as when driving or holding the phone. Some people wake up at night because their fingers are numb.
- Weakening of the grip and difficulty with finger coordination (such as typing or playing an instrument) may occur. These symptoms are usually seen in more severe cases of nerve compression.
- If the nerve is very compressed or has been compressed for a long time, muscle wasting in the hand can occur. Once this happens, muscle wasting cannot be reversed. For this reason, it is important to see your doctor if symptoms are severe or if they are less severe but have been present for more than 6 weeks.