In many cases of cubital tunnel syndrome, the exact cause is not known. The ulnar 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 must stretch around the boney ridge of the medial epicondyle. Because this stretching 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, which 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.

• 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.
• The feeling 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.
• 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

Medical History and Physical Examination

Your doctor will discuss your medical history and general health. He or she may also ask about your work, your activities, and what medications you are taking.

After discussing your symptoms and medical history, your doctor will examine your arm and hand to determine which nerve is compressed and where it is compressed. Some of the physical examination tests your doctor may do include:

• Tap over the nerve at the funny bone. If the nerve is irritated, this can cause a shock into the little finger and ring finger (Tinel’s sign) — although this can happen when the nerve is normal as well.
• Check whether the ulnar nerve slides out of normal position when you bend your elbow.
• Move your neck, shoulder, elbow, and wrist to see if different positions cause symptoms.
• Check for feeling and strength in your hand and fingers.

Figure: Nerve conduction studies measure the signals travelling in the nerves of your arm and hand.

Your doctor may recommend surgery to take pressure off of the nerve if:

• Nonsurgical methods have not improved your condition
• The ulnar nerve is very compressed
• Nerve compression has caused muscle weakness or damage

There are a few surgical procedures that will relieve pressure on the ulnar nerve at the elbow. Your orthopaedic surgeon will talk with you about the option that would be best for you.

These procedures are most often done on an outpatient basis, but some patients do best with an overnight stay at the hospital.

Cubital tunnel release:
In this operation, the ligament “roof” of the cubital tunnel is cut and divided. This increases the size of the tunnel and decreases pressure on the nerve.

This illustration shows the path of the ulnar nerve through the cubital tunnel. Structures that may compress the nerve — such as the medial epicondyle and ulnar collateral ligament — are also shown.

After the procedure, the ligament begins to heal and new tissue grows across the division. The new growth heals the ligament, and allows more space for the ulnar nerve to slide through.

Cubital tunnel release tends to work best when the nerve compression is mild or moderate and the nerve does not slide out from behind the bony ridge of the medial epicondyle when the elbow is bent.

In this surgical photo, a cubital tunnel release has been performed to decompress, or relieve pressure on, the ulnar nerve. The arrow shows the portion of the nerve that has become narrowed over time due to compression.

Ulnar nerve anterior transposition.

In many cases, the nerve is moved from its place behind the medial epicondyle to a new place in front of it. Moving the nerve to the front of the medial epicondyle prevents it from getting caught on the bony ridge and stretching when you bend your elbow. This procedure is called an anterior transposition of the ulnar nerve.

The nerve can be moved to lie under the skin and fat but on top of the muscle (subcutaneous transposition), or within the muscle (intermuscular transposition), or under the muscle (submuscular transposition).

Another option to release the nerve is to remove part of the medial epicondyle. Like ulnar nerve transposition, this technique also prevents the nerve from getting caught on the boney ridge and stretching when your elbow is bent.

The results of surgery are generally good. Each method of surgery has a similar success rate for routine cases of nerve compression. If the nerve is very badly compressed or if there is muscle wasting, the nerve may not be able to return to normal and some symptoms may remain even after the surgery. Nerves recover slowly, and it may take a long time to know how well the nerve will do after surgery.