Ulnar Nerve Entrapment / Cubital Tunnel Syndrome
What is cubital tunnel syndrome?
This condition is caused by one of the nerves in your arm (the ulnar nerve) being tightly compressed between bone and a strap ligament next to the elbow. The area involved is on the inside of your elbow (see picture). The strap runs between the medial epicondyle and the tip of the elbow, trapping the nerve in the dip between the two (you can easily feel this on yourself). This dip is called the cubital tunnel, hence the medical name. When the nerve is compressed enough it starts to malfunction and abnormal sensations are felt in the little and ring fingers.
What causes cubital tunnel syndrome?
Anything that causes swelling inside the tunnel or stretches the nerve against the bone can cause this syndrome. Sleeping with the elbow tightly bent is a frequent cause. Sometimes the nerve is not well strapped down and slips around the tip of the epicondyle every time the elbow is moved, causing repeated minor injury to the nerve.
What are the symptoms of cubital tunnel syndrome?
Symptoms often come on gradually and start with pins and needles in the ring and little fingers sometimes associated with pain and discomfort around the inner side of the elbow. Often this is worse with the elbow bent eg at night or when using the phone. Numbness and weakness may follow if the pressure is severe and the nerve becomes more damaged. The hand becomes clumsy and weak and the small muscles between the hand bones waste away.
How is the diagnosis of cubital tunnel syndrome made?
A good story and examination often confirm the diagnosis but other conditions can mimic cubital tunnel syndrome , or co-exist with it, and must be carefully excluded. An elbow xray is sometimes useful and electrical tests of the nerve will often be used to confirm the diagnosis.
What is the treatment of cubital tunnel syndrome?
Unless the symptoms are intermittent and settle rapidly surgery is usually indicated to avoid irreversible nerve damage.
Pressure is relieved by carefully dividing the strap ligament over the nerve at the elbow. If the nerve is slipping around the medial epicondyle it may be necessary to move the nerve in front of the bone (anterior transposition) or trim off the tip of the bone (medial epicondylectomy). The operation is usually done under a general anaesthetic as a day case procedure. Relief of pain and pins and needles is usually rapid. If the hand was numb or weak before surgery the nerve function usually only partially recovers and that recovery can take up to 2 years.