The ulnar nerve is a large nerve that goes from the arm, across the back of the elbow, down the forearm and into the hand. This nerve carries signals for sensation from the little and ring fingers and part of the hand back to the brain. It also carries signals from the brain to activate the small muscles in the hand, which are important for strong gripping, pinching and fine control of the fingers.
(Diagram of ulnar nerve and cubital tunnel)
As the nerve goes behind the elbow, it is goes through a narrow space called the cubital tunnel, with a band of tissue going across to hold the nerve in place. In some people, this space becomes narrower than usual because of bone spurs (osteoarthritis) or thickening of the band of tissue. This increases the pressure on the nerve as it goes through the cubital tunnel, affecting its ability to conduct signals properly. When the elbow is flexed, the pressure increases further. This “conduction block” causes the numbness or tingling in the fingers and weakness of the muscles in the hand. The symptoms are initially mild and go away quickly when the elbow is straightened and the hand is shaken vigourously. Eventually, over several months to years, the numbness and tingling become more constant and the muscles in the hand start to shrink and the hand develops more sunken or hollow spaces where the muscles used to be. The hand becomes much weaker and there is difficulty doing things that require dexterity and fine finger movements such using chopsticks, keys and buttons. Because the small muscles also help to straighten the little and ring fingers and bring them together, these fingers become bent and separated from the rest of the fingers.
If you have these symptoms, see a hand specialist for a full neurological examination and some investigations. These investigations include:
In the early stages of cubital tunnel syndrome, it may be possible to minimize pressure and tension on the nerve by not keeping the elbow flexed for too long when doing things with the hands. Physical therapy with “nerve gliding exercises” to loosen the nerve at the elbow helps to relieve the tightness. A splint is used at night to keep the elbow straight while sleeping.
In more severe or later stages, especially when there is weakness of the hand muscles, surgery is needed. The ulnar nerve behind the elbow and in the forearm is completely freed from any bands of tissue that are crossing it, thus relieving any compression and pressure on the nerve. This is usually done with a 10cm long incision across the back of the elbow to expose the nerve in this area. It can also be done by a minimally invasive procedure (endoscopic cubital tunnel release) with a 2-3cm incision using a camera and special equipment. Following this release, the nerve may become very loose and keep slipping across the bone at the elbow. If this happens, the nerve has to be secured in front of the elbow either under the forearm muscles (submuscular anterior transposition) or under a sling of tissue on the muscles (subfascial anterior transposition). This decreases pressure and tension on the nerve when the elbow flexes, and prevents it from becoming injured by frequent rubbing against the bone during elbow movements. Following surgery, nerve gliding exercises are started to keep the nerve moving and to prevent it from getting stuck in scar tissues.
Aftercare: Prevention of Complications