Ulnar nerve entrapment


Ulnar nerve entrapment occurs when there is pressure over the ulnar nerve and it is most common at the elbow, where the nerve runs behind the bony lump on the inside of the joint.  It is also called cubital tunnel syndrome or ulnar nerve neuritis.

The ulnar nerve originates in the neck and travels down the arm and forearm towards the hand. As it crosses behind the elbow joint, the nerve passes through a tunnel formed by muscle and ligament on the inside edge of the elbow. This is the cubital tunnel and it helps to keep the ulnar nerve in the correct place and let it slide freely when you bend and straighten the elbow. You may be able to feel it if you straighten your arm out and rub the groove on the inside edge of your elbow. It is a cord like structure which is rather uncomfortable to touch even in the normal subject.

The ulnar nerve supplies sensation to the little finger and half the ring finger. It works the muscle that pulls the thumb into the palm of the hand, and it controls the small muscles (intrinsics) of the hand.


Cubital tunnel syndrome has several possible causes. The problem may be with the nerve itself or with surrounding structures. The nerve has to slide in the tunnel when the elbow bends and actually stretches a small amount to allow for this. If the anatomy changes around the elbow for example, in arthritis, then the nerve may need to stretch more and so may not work as effectively. If your elbow does not go fully straight then this can bring on symptoms, as the nerve has to travel further than if the elbow were straight, so the nerve is stretched. If the structures that usually keep the ulnar nerve behind the elbow fail, the nerve can flick around the medial epiciondyle (bony lump) and this can give symptoms from the nerve. If the nerve itself becomes larger from inflammation or injury then the available space in the tunnel is effectively smaller so the nerve can then become symptomatic. External pressure can also cause symptoms, for example leaning on the elbows when sat at a desk or putting your elbow on the car door trim when driving.


Numbness, tingling (pins and needles) or pain on the medial (inside) border of the hand and in the ring and little fingers is common. The numbness is often felt when the elbows are bent for long periods, such as when sleeping. Later problems can be clumsiness of the hand as the muscles become affected. Tapping or bumping the nerve in the cubital tunnel will cause an electric shock sensation down to the little finger.


The cubital tunnel is the commonest, but only one of several spots, where the ulnar nerve can get squashed. Your doctor will try to find the exact spot that is causing your symptoms which may involve having special tests done called nerve conduction tests. One common test is the nerve conduction velocity (NCV) test. The NCV test measures the speed of the impulses traveling along the nerve and impulses are slowed when the nerve is compressed or constricted. The NCV test is sometimes combined with an electromyogram (EMG). The EMG tests the muscles of the forearm that are controlled by the ulnar nerve to see whether the muscles are working properly. If the muscles are not it may be because the nerve supply is a problem.



The simplest and first measure should be to stop doing whatever may be causing the symptoms (avoidance). If you sleep with your elbows bent, you can try splints which stop you bending your elbows at night. If you tend to lean on your elbows a lot, try avoiding doing this. Behaviour alteration may be all that is required. Anti-inflammatory medications may help control the symptoms.


Ultimately if your symptoms do not go away, you may be offered ulnar nerve release at the elbow. The aim of surgery is to release the pressure on the ulnar nerve where it passes through the cubital tunnel. Usually it is only necessary to release the pressure on the nerve by incising the tissue that forms the roof of the cubital tunnel. This is called an ulnar nerve decompression. Sometimes the ulnar nerve is unstable and flicks from behind to infront of the elbow. If this is the case then your surgeon may combine decompression with a transposition procedure. This means the nerve is lifted from its bed behind the medial epicondyle and secured under tissue on the front to the joint. Not only does this stabilise the nerve and stop it flicking but also it has less distance to travel in front of the joint than behind. Less distance means less stretching. The dissection of the nerve is much greater in a transposition than in a decompression and so the chance of accidental nerve damage is greater. Most surgeons would perform a transposition only when the nerve is unstable and a decompression when there is just evidence that the nerve is under pressure.

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