Cubital tunnel syndrome (CUTS) is the second most common nerve compression following carpal tunnel syndrome and is caused by compression of the ulnar nerve located behind the elbow. Patients with CUTS often experience pain along the inside of the elbow and numbness in the 4th and 5th fingers, which may occur gradually or following a trauma. Symptoms may occur at night and awaken patients from sleep or during the day with activities which require bending the elbow such as reading and driving or when the elbow is leaned upon. At first, the symptoms will come and gobut as the damage to the ulnar nerve increases the numbness in the 4th and 5th fingers becomes more frequent or even constant.
The ulnar nerve supplies many of the small muscles in the hand. In severe cases of CUTS these muscles may behave as if the nerve has been cut and begin to atrophy or shrink in size. The hand may become clumsy with repetitive tasks and patients often complain of dropping items from the hand. The hand may develop a bony appearance as muscle atrophy progresses. This is most noticeable in the muscle between the index finger and the thumb. Deformities of the hand and clawed fingers may develop in longstanding severe cases due to muscle imbalance.
A thorough history about the location of the numbness and activities that make the numbness better or worse is important. During physical examination tenderness is noted along the inside of the elbow and usually behind the “funny bone”. With motion of the elbow the nerve may be found to slide in front of the “funny bone”. Tapping upon the nerve will send tingling sensations into the forearm or fingers. If the elbow is bent and pressure applied to the nerve the numbness may be reproduced. X-rays are usually normal but may show bone spurs or deformities that could compress the nerve as well.
Initial treatment usually includes avoiding direct pressure on the elbow and avoiding prolonged or repetitive bending of the elbow. A splint applied to the front of the elbow with only a slight bend can be worn at night. If symptoms persist or worsen in spite of conservative care over several weeks, an EMG/ NCV test is usually ordered to determine the degree of ulnar nerve damage and whether other sites of nerve compression in the arm or neck are present which may contribute to the symptoms.
If nerve damage is detected and symptoms are not improving surgery may be required. Surgery involves releasing any tight bands around the nerve and placing the nerve in a protected position beneath the forearm muscles to prevent further damage. The goal of surgery is to prevent progressive deterioration of the nerve and provide an optimal environment for the nerve to heal. In cases where the numbness had become constant or muscle weakness occurs before surgery the nerve may not completely heal. If additional sites of compression are identified such as a herniated disk in the neck or thoracic outlet syndrome, symptoms may improve but the additional compression sites may need to be addressed to achieve complete relief.
After surgery a skilled hand or occupational therapist is needed to restore strength and motion to return the arm to a healthy state.