Cubital Tunnel Syndrome

Anatomy

Cubital tunnel syndrome results from pressure or local entrapment of the ulnar nerve at the elbow.  It is the second most common nerve entrapment of the upper extremities, after carpal tunnel syndrome.

The ulnar nerve passes from the upper arm to the inner side of the elbow, where it travels beneath a bony bump called the medial epicondyle.  This area is commonly referred to as the “funny bone.”  Unlike many nerves in the extremities, the ulnar nerve lies directly against the bone and close to the skin at the elbow.  This makes the ulnar nerve more susceptible to injury.

The ulnar nerve consists of different types of nerve fibers.  Some fibers carry information about sensations experienced by the skin from the small finger and the outer half of the ring finger, while others control some of the muscle movements in the forearm and most of the small muscles in the hand responsible for fine movements.

Causes

When pressure on the nerve becomes great enough to alter the way that the nerve works, numbness, tingling or pain may result.  Pressure may be caused by keeping the elbow bent for long periods of time, leaning on the inside of the elbow for extended periods or a direct blow to the area.  Soft tissues overlying the nerve can potentially become overgrown, also leading to increased pressure on the nerve.

Symptoms

Numbness, tingling and pain are common symptoms in cubital tunnel syndrome.  These symptoms occur most frequently in the ring and small fingers and are typically present when there is increased pressure on the nerve, as when leaning on the elbow or repetitively bending and straightening it.  In more advanced cases, there may be clumsiness in the hand and weakness of grip or pinch.  When the compression is severe, muscle wasting may be seen in the hand.

Diagnosis

A thorough history and physical examination suggest the diagnosis and help to identify the involvement of the ulnar nerve.  They also serve to eliminate other medical conditions that may result in similar types of symptoms.  Nerve conduction studies help to confirm the injury to the ulnar nerve and, in many cases, can determine the location of the pressure or entrapment.  Electromyography (EMG) can help to determine the severity of the nerve injury, the relative age of the injury and the presence or absence of nerve healing.

Treatment

It stands to reason that, if direct pressure on the nerve or prolonged bending of the elbow can bring on the problem, avoidance of these activities may be useful in treating it.  Elbow pads or braces can be useful to protect the nerve and to keep patients from bending the elbow fully.  Non-steroidal anti-inflammatory medicines can help to decrease pain and inflammation, while physical or occupational therapy can be useful in relieving pain and stiffness.  Therapists can also instruct patients in exercises that can help the ulnar nerve glide more easily through the cubital tunnel.

If nerve function testing shows that injury to the nerve is severe, or if a patient has no relief with non-surgical methods of treatment, surgery may by be required to relieve pressure on the nerve.  Different techniques can be used, from surgical release or opening of the cubital tunnel to repositioning of the ulnar nerve.  In some cases, the medial epicondyle may be trimmed down.

The success rate for routine cases of nerve compression is similar for each surgical method.  Numbness and tingling may improve slowly or quickly.  It may take several months for strength in the affected areas to improve.  The pain, numbness or weakness from cubital tunnel syndrome may not resolve completely, particularly in severe cases.