Cubital tunnel syndrome

WHAT IS IT?.

Cubital tunnel syndrome (CuTS) is a condition where the ulnar nerve is compressed at the elbow in a location called the cubital tunnel. Conditions like this are frequently referred to as "trapped" nerves.  The compression of the nerve affects the blood supply to the nerve and also the flow of nutrients and structural elements within the nerve. This results in symptoms.

The cubital tunnel is formed by fascia (a layer of tissue covering muscles of the forearm) and bone (a bump of bone at the inner side of the elbow called the medial epicondyle) . The cubital tunnel is sometimes referred to as the "funny bone". The ulnar nerve provides sensation to the little finger and half the ring finger. It also provides function to the muscles in the fleshy pad at the little finger side of the heel of the hand (hypothenar eminence).These muscles control the dexterity and mobility of the little finger. The ulnar nerve also controls muscles that enable you to spread your fingers.

CAUSE

In most cases there is no specific cause for the compression of the nerve . In a small proportion of cases the following causes may be underlying:-

• prolonged pressure in the region of the cubital tunnel such as when leaning on the inner side of the elbow with it flexed
• activities that involve repeated or prolonged flexion of the elbow
• fracture or ligament injury of the elbow recent or previously
• arthritis of the elbow
• diabetes

SYMPTOMS

There are typical symptoms of cubital tunnel syndrome, however not everybody with cubital tunnel syndrome gets all these symptoms.

Tingling of the fingers

The fingers affected  in cubital tunnel syndrome are commonly the little and  ring fingers. Tingling of these fingers is experienced by some people as "pins & needles" or a "buzzing" or warmth of the affected fingers.

The tingling may not be there all the time. It may occur after use of the arm or may also occur when the arm is not moved for sometime, such as when driving or holding a newspaper. The common underlying cause is the elbow being held in a flexed position. It is also frequently experienced at night when asleep, and wakes the person up. Patients with this frequently describe either having to straighten the elbow or shake the hand to get the feeling back to normal.

If the tingling is constantly present, you should see your GP for a referral to a hand surgeon sooner as potentially the function of the nerve is at risk for permanent damage.

Numbness of the fingers

This affects the same fingers as the tingling. Typically it tends to be also at night along with the tingling. It may also be on waking first thing in the morning.

The numbness may not be there all the time. If the numbness is constantly present, you should see your GP for a referral to a hand surgeon sooner as potentially the function of the nerve is at risk for permanent damage.

Pain

Pain in the hand, inner forearm and elbow is also frequently present.

Weakness of the hand

The weakness results in difficulty with writing, cutting food with a knife and/or typing on a keyboard. Also the pinching grip between thumb & index finger is weaker.

Muscle wasting

Loss of bulk (muscle wasting) in the fleshy pad at the little finger side of the heel of the hand (hypothenar eminence) may be noted in late stages. A hollow may also develop in the webspace between the index finger and thumb due to muscle wasting. If you have tingling or numbness with this muscle wasting you should seek urgent referral from your GP to a hand surgeon.

Other symptoms

Cramps of the muscles of the hand may also be described. Aching pain or discomfort in the forearm & elbow is also sometimes experienced. The little finger may also involuntarily be spread away from the ring finger. The little and ring fingers may also involuntarily become curved (claw hand posture).

DIAGNOSIS

In the majority of cases the history of symptoms and an examination is sufficient to make the diagnosis. In some cases, additional investigations may be required such as an electrodiagnostic test (nerve conduction study with electromyography/EMG). The need for this test is usually decided by Mr Miranda once he has seen you. It is done when there are atypical symptoms or if there is a possibility of another nerve compression. Blood tests or X-rays may also be required if underlying causes are suspected.

TREATMENT

Non-surgical Treatment

This can be effective in milder cases of the condition. Adjusting the pattern of use of the arm can be effective. What is meant by this is avoidance of prolonged flexed elbow and avoidance of pressure on the inner side of the elbow such as leaning on it.  In some cases a splint for night time use may be helpful in reducing or abolishing the night time symptoms. A session with the upper limb therapist to learn ways of reducing pressure on the ulnar nerve can be very helpful.

Surgical Treatment

There are three possible operations to treat cubital tunnel syndrome. The operation is done under general anaesthetic in the majority of cases. In most cases an opening of the roof of the cubital tunnel  (decompression) is sufficient. If there is a deformity of the cubital tunnel such as due to previous fracture or underlying elbow arthritis, the nerve may need to be decompressed and moved to the front of the elbow (transposition). Removal of the medial epicondyle (epicondylectomy) is another option. Mr Miranda will  advise you on the technique most appropriate to your problem.

If the symptoms are intermittent before the operation, the symptoms may be relieved within a few weeks of the operation. In other cases, it may take a few months for relief of the symptoms after the operation. The scar may take a about 6 to 8 weeks to stop being tender. Return to full grip strength may also take a similar time. In some cases, the symptoms never completely go away due to permanent damage to the ulnar nerve present before the operation.