Cubital Tunnel Syndrome (Ulnar Nerve Entrapment)

Ulnar nerve entrapment (cubital tunnel syndrome) occurs when the ulnar nerve in the arm becomes compressed. When this happens, the nerve does not function normally causing pain and numbness.

Anatomy
The ulnar nerve is one of the three main nerves in the arm. It travels from under the collarbone and along the inside of the upper arm. It passes through a tunnel of tissue (the cubital tunnel) behind the inside of the elbow. Beyond the elbow, the nerve travels under muscles on the inside of the forearm and into the 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 nerve functions to give sensation to the little finger and the half of the ring finger that is near the little 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 to make a strong grip.

You can feel the nerve superficially through the skin along the cubital tunnel and it is commonly called the "funny bone.”

Cause
It is not known exactly what causes compression of the ulnar nerve at the elbow. Some factors can make it more likely that the nerve will be compressed. These include:

• Prior fractures of the elbow
• Bone spurs
• Swelling of the elbow joint
• Cysts
• A direct blow to the inside of the elbow
• Leaning on the elbow for prolonged periods
• Repetitive activity that requires a bent elbow

Symptoms
Ulnar nerve entrapment can give symptoms of numbness, tingling or "falling asleep" in the ring finger and little finger. Symptoms may come and go, but happen more often when the elbow is bent, such as when driving or holding the phone. There may be an aching pain on the inside of the elbow. 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 also occur.

If the nerve is severely compressed or has been compressed for a long time, muscle wasting in the hand can occur. Once this happens, muscle wasting cannot be reversed.

Treatment
Unless there is a lot of muscle wasting, Dr. Samimi will recommend nonsurgical initial treatment.

Activity Modification

• Avoid frequent use of the arm with the elbow bent
• If you use a computer frequently, make sure that your chair is not too low.
• Do not rest the elbow on the armrest.
• Avoid leaning on the elbow or putting pressure on the inside of the arm.
• Keep the elbow straight at night when you are sleeping. This can be done by wrapping a towel around the straight elbow, wearing an elbow pad backwards, or using a special brace.

Loosely wrapping a towel around the arm with tape can help you to remember not to bend the elbow during the night.

Nonsteroidal-Anti-Inflammatory Medication
Anti-inflammatory medicine such as ibuprofen or Motrin may help reduce swelling around the nerve and alleviate pain. Steroid (cortisone) injections around the ulnar nerve are not generally used because there is a risk of damage to the nerve.

Surgery
If the strategies listed above do not help improve the condition; if the nerve is very compressed; or if there is muscle wasting, Dr. Samimi may recommend surgery to take pressure off of the nerve.

Surgery for cubital tunnel syndrome involves releasing any adhesions around the ulnar nerve and moving the nerve from its place behind the elbow to a new place in front of the elbow. This 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 under the muscle (submuscular transposition).

Dr. Samimi will move the nerve from behind the elbow to in front of it and will make sure that it is not compressed by any other structures. A similar skin incision is used regardless of how deep under the skin the nerve is moved.

The surgery is usually done on an outpatient basis or with an overnight stay in the hospital. Depending on the type of surgery, you may need to wear a splint for a few weeks after the operation.

The results of the cubital tunnel syndrome surgery are generally very good. 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 can take a long time to know how well the nerve will do after surgery.