Ulnar nerve entrapment

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What is ulnar nerve entrapment?

The ulnar nerve travels from your shoulder to your little finger. It is located quite close to the skin’s surface without much muscle and bone to protect it. It is this nerve that is responsible for the painful sensation you get when you hit your funny bone. The ulnar nerve is particularly vulnerable to compression. There are two types of ulnar nerve entrapment:

  • Cubital tunnel syndrome occurs on the inside of your elbow under a bump of bone commonly known as the funny bone (the medial epicondyle). This is the most common place for ulnar nerve entrapment.
  • Ulnar tunnel syndrome occurs when the nerve gets trapped in a canal at your wrist and is less common.

What causes ulnar nerve entrapment?

The ulnar nerve passes round the back of your elbow and through a tight tunnel between the muscles of your forearm. Entrapment occurs if this tunnel becomes too tight.

This can be the result of strain caused by repetitive movements with your arm or hand, previous elbow injury or associated with other medical conditions. Bending your elbow stretches your ulnar nerve behind the bump of your funny bone and keeping it bent for extended periods can cause irritation. This can occur if you hold a phone up to your ear for long periods of time or use a tool in a fixed position, for example. Other possible causes include an injury to your elbow, arthritis or a cyst. Wrist entrapment may also be caused by a cyst, which puts pressure on your wrist joint as it grows.

Among the factors that put you at greater risk of ulnar nerve entrapment are:

  • Obesity
  • Diabetes
  • High blood pressure
  • Autoimmune conditions
  • Thyroid conditions
  • Pregnancy

What are the symptoms of ulnar nerve entrapment?

Symptoms will vary according to where the entrapment is and they may worsen at night or at certain points during the day.

If the entrapment is at your elbow you may experience:

  • An ache on the inside of your elbow
  • Numbness in your little finger and ring finger
  • Pins and needles
  • Difficulty moving your fingers
  • A weakened grip

If the problem becomes severe it can lead to:

  • Muscle wasting in your forearm or hand
  • Deformity of your little finger and ring finger

If the entrapment is at your wrist you may experience:

  • Pain, numbness or weakness in your hand
  • Tingling in your little finger and ring finger
  • A weakened grip
  • Difficulty moving your fingers

If the problem becomes severe it can lead to:

  • Muscle weakness and wasting

How is ulnar nerve entrapment diagnosed?

A physical examination of your arm, elbow and hand will test for strength, sensation and signs of nerve irritation. An X-ray may be used to rule out other causes of elbow pain such as injury, trauma or arthritis. An MRI or ultrasound scan can provide a detailed view of the tissues of the arm and hand. An orthopaedic consultant may use an electromyogram to measure the electrical impulse travelling along the nerves, nerve roots and muscle tissue. By inserting a tiny needle electrode through the skin into the muscle, it is possible to measure the amount of electricity generated by the muscle cells when activated by the nearby nerves. If the little finger or ring finger feels numb or tingly, the consultant may carry out a nerve conduction study to assess for nerve damage. The nerve is stimulated and the time it takes to respond is measured.

How is ulnar nerve entrapment treated?

A physiotherapist can recommend some simple exercises to relieve symptoms and you can also change some of your postural habits to relieve pressure on your elbow, such as using your phone on speakerphone or with headphones. You can use ice and anti-inflammatories to soothe inflammation and you may need to wear a wrist splint if you have entrapment of the wrist. For severe or long-standing problems, there are a range of surgical options depending on your individual problems which your consultant will discuss with you.

The most commonly performed procedure is ulnar nerve decompression. This is a surgical procedure performed under local, regional or general anaesthetic. An incision is made along the elbow, revealing the ulnar nerve. The orthopaedic surgeon then releases any compressive forces that are affecting the nerve and closes the incisions with sutures.