Ulnar Nerve Compression

The Ulnar nerve supplies feeling to the little finger and the adjacent half of the ring finger and also to the little finger side of the hand. It innervates the small muscles of the hand which allow you to spread your fingers apart and bring them back together again. In the forearm it gives branches to the muscles which bend (flex)  your little and ring fingers and that side of the wrist.

Causes

There are several causes of ulnar nerve compression. They include;

  • There are multiple sites where the nerve can get pressed on thus causing the nerve not to work fully. These points typically are around the elbow region or the wrist. There are several “tunnels” formed by muscles, ligaments and / or the bone where constriction of the nerve may occur.
  • External pressure on the nerve from masses such as ganglions or bony spikes (osteophytes with arthritis)  from the elbow joint or wrist joint`
  • Traction –as you bend the elbow repeatedly it stretches the nerve as it runs behind the “funny bone” at the elbow.  In some people this repeated stretching may irritate the nerve

Symptoms

The typical symptoms that may develop are;

  • Numbness of the ring, little +/- side of the hand. This initially may be intermittent and associated with certain positions of the arm, especially at the elbow. As it becomes more severe it becomes constant.
  • Weakness of the small muscles of the hand may result in weakness of spreading the fingers, pinch and grip. The muscles between the bones in your hand may become wasted leading to a dip between the hand bones.
  • Weakness in the forearm muscles is less noted but may contribute to grip weakness

 

Investigations

  • Nerve conduction studies are usually performed to confirm the diagnosis and can also help localize the area of  compression i.e. the wrist or elbow
  • An X-ray and ultrasound may be ordered if there are signs suggestive of a ganglion or arthritis as the cause of the nerve compression. Rarely would a CT or MRI scan be required.

Treatment

If mild, conservative treatments can be trialed. These include the use of an elbow  splint to keep the elbow straight whilst sleeping at night and avoidance of activities which may irritate the nerve such as repetitive tasks that involve elbow flexion or resting on the elbow. A cortisone injection may be carried out to reduce swelling in and around the nerve.

If symptoms are more severe or these conservative measures fail surgery is usually recommended.

Surgery

 If the compression is at the elbow, the surgery involves making a long cut behind the elbow approximately 15cm long. The nerve is explored along its course and any areas of tight constriction by ligaments or muscles are released. If no areas of tightness are found the nerve may be transposed to in front of the elbow to reduce repeated traction on it with elbow bending.  The wound is closed with a dissolving stitch beneath the skin and a bulky bandage is placed around the elbow. If the wound is oozy a drain tube may be inserted at surgery which stays in overnight and is removed usually the following day.  This surgery is usually done as day case in hospital. The fingers may be more numb for the first 4 to 24 hours due to local anaesthetic being placed in the wound at operation.  It is essential that you keep your fingers gently bending and straightening from day one to avoid this. Do not squeeze a ball. You may use your hand for light tasks after the first day.

For the first week the dressing needs to remain dry and the arm will need to be placed in a large plastic bag for showering. After a week you will be seen and the dressing changed to a lighter dressing that may usually get wet under the shower. It is usually about 6-8 weeks before you can comfortably rest your elbow on things. Movement is usually reduced for the first 2-3 weeks slightly by the dressing, mild swelling and discomfort.

If the compression is at the wrist a smaller incision approximately 4-5cm long is made over  the little finger side of the wrist and palm. The nerve is identified and once again any constricting ligaments or muscles are released. It is stitched up with nylon stitches and then placed in a splint and bandage which do not allow movement at the wrist but allows the fingers to bend.  The fingers may be more numb for the first 4 to 24 hours due to local anaesthetic being placed in the wound at operation.   This remains on for 2 weeks. It is essential that you keep your fingers gently bending and straightening from day one to avoid this. Do not squeeze a ball. You may use your hand for light tasks after the first day. After 2 weeks the stitches are removed and hand therapy exercises are started. It is usually 6-8 weeks before the scar can tolerate firm pressure on it. Grip strength will often be reduced for 2-3 months after the surgery.

Complications                  

  • General anaesthetic – nausea and vomiting, heart attack, deep vein thrombosis and pulmonary embolus, allergy to anaesthetic drugs, death
  • Infection – with all wounds there is a small risk of infection of approximately 2%
  • Bleeding
  • Tender,  lumpy scar
  • Swelling and stiffness of the hand –Neuroma – i.e. a  “knot” on a cut skin nerve in the scar can result in a very tender spot in one area of the scar
  • Regional pain syndrome – the hand becomes swollen, stiff, warm, hairy and may be painful. It is related to “trauma” to the limb and not to the specific type of surgery. It may  take months  to years to settle fully and may require additional medication or treatment by a pain specialist

Outcome

The pins and needles that come and go usually resolve in most people straight after the surgery. For people who have persisting numbness and weakness prior to the surgery it depends on how much damage the nerve has suffered and for how long as o whether it will recover or not. If there has been weakness and wasting of the muscles for over a year the recovery rate is not high. Surgery is still usually worthwhile though to prevent the damage worsening. Overall about 70-80% of patients iprove with surgery but less achieve full recovery. Some altered sensation may remain in the fingers but hopefully less dense than preoperatively. The sensation may take up to a year to recover.

If surgery fails to improve the symptoms and ongoing compression is found on nerve conduction studies then a more complicated surgery can be undertaken where the nerve is wrapped in the muscle or a vein graft.