What is ulnar nerve entrapment?
Ulnar nerve entrapment is a compression neuropathy that happens when the ulnar nerve becomes trapped or squeezed, and it can lead to damage that gets worse over time.
The ulnar nerve is one of the 3 main branches of the brachial plexus, a network of nerves that starts in the cervical spinal cord and runs down the arm. After leaving the spinal cord, the plexus runs along the armpit to the inner side of the upper arm and forearm, then down to the hand. Ulnar nerve entrapment can happen anywhere along the path of the nerve, for example below the collarbone, at the elbow and upper arm, or even in the far part of the hand or at the wrist in Guyon’s canal. The most common site of compression is the elbow, usually because of cubital tunnel syndrome (also called ulnar nerve compression syndrome at the elbow).
Ulnar nerve entrapment is the 2nd most common compressive peripheral neuropathy, after carpal tunnel syndrome (compression of the median nerve). Still, carpal tunnel syndrome should not be confused with cubital tunnel syndrome. The symptoms look alike and both involve compression in the arm, but cubital tunnel syndrome affects the ulnar nerve, while carpal tunnel syndrome affects the median nerve.
Causes
The most common type of ulnar nerve entrapment at the elbow is cubital tunnel syndrome. It can be caused by an elbow injury (such as a fracture or dislocation), bone and joint disease (such as arthritis or bone spurs), or too much pressure on the elbow, especially on hard surfaces.
When you bend your elbow, the ulnar nerve is stretched around the medial epicondyle. This stretching can irritate the nerve, so keeping the elbow bent for a long time or bending it over and over (common in some kinds of heavy work) can cause pain and numbness. For example, many people sleep with their elbows bent, which adds to the pressure on the ulnar nerve and can wake them in the night with numb, stiff fingers.
Too much fluid building up at the elbow can press on the nerve, for example a swollen, inflamed synovial sac or a synovial cyst.
In addition, some conditions can make the nerve more sensitive to compression, such as diabetes and hereditary neuropathy with pressure palsies (HNPP).
Sometimes the cause of ulnar nerve entrapment at the elbow cannot be found.
Ulnar nerve entrapment at the wrist can be caused by a direct injury, a cut, a ganglion cyst, or ulnar tunnel syndrome at the wrist (Guyon’s canal syndrome). Blood vessel malformations and some joint abnormalities, such as rheumatoid arthritis, and other disorders can also contribute to compression of the nerve. Finally, too much cycling and push-ups, as well as any other common source of long-term, repeated pressure from outside, such as hand tools or the handle of a cane, may also contribute to ulnar nerve entrapment at the wrist.
Symptoms
The symptoms of ulnar nerve entrapment can vary depending on the location, extent and severity of the pressure on the nerve, as well as which branches of the ulnar nerve are involved.
Typical symptoms may include muscle weakness, a weaker grip and clumsiness (trouble typing or playing a musical instrument, and so on). In some cases, it can also lead to muscle wasting.
In addition, a compressed ulnar nerve can cause numbness, tingling (paresthesia) and pain in the little finger, the little-finger side of the ring finger and the inner edge of the palm (the raised pad below the little finger). These symptoms come and go, and appear more often when the elbow is bent, for example while driving or using a phone.
Fingers 4 and 5 feel numb and stiff, especially when the elbow is bent, and they can become hard to move. Severe damage to the ulnar nerve at the elbow can make fingers 4 and 5 curl in (ulnar claw hand). Over time, damage to the ulnar nerve can get worse and lead to permanent disability.
Many patients know the typical tingling that comes from hitting the “funny bone”. Anatomically, this bone is called the medial epicondyle of the elbow, the bump on the lower inner end of the upper arm bone. Hitting it may not be very “funny”, and in some cases it can cause injury, because the ulnar nerve runs very close to the surface at this spot and is easily hurt.
How long does ulnar nerve entrapment last?
When you hit your “funny bone” at the elbow, the tingling may last only a few seconds or a few minutes. On the other hand, the symptoms of ulnar nerve entrapment can become chronic and last a very long time. If the symptoms get worse or last longer than 2-3 months, before or after conservative treatment, you need to see a doctor.
Diagnosis
Diagnosing ulnar nerve entrapment starts with taking your medical history, followed by an examination of the structure of the arm, elbow and hand to check movement and sensation, and to find the source of the damage:
- Tapping on the “funny bone”. If the nerve is irritated, this can send a jolt down into the little finger and ring finger (Tinel’s sign).
- Checking whether the ulnar nerve slips out of place when you bend your elbow.
- Moving the neck, shoulder, elbow and wrist to see which positions bring on the symptoms.
- Checking sensation and muscle strength in the hand and fingers.
Supporting tests such as X-rays, ultrasound, electromyography and nerve conduction studies may be done to confirm the diagnosis and to help locate the nerve damage and judge how severe it is. Electromyography and nerve conduction studies are 2 non-invasive electrodiagnostic methods that can be used to assess the electrical activity of the muscles and of the nerves, respectively.
Treatment
Mild cases of ulnar nerve entrapment can get better on their own without treatment. In some cases, pain and inflammation can be treated with medicines such as nonsteroidal anti-inflammatory drugs (NSAIDs). Other pain medicines that may be prescribed include tricyclic antidepressants, especially for people who cannot take NSAIDs.
Some movements and positions should be avoided. For example, do not keep your elbow bent for long periods; you may even need to wear a splint to keep the joint still. Physical therapy can also be added, such as ulnar nerve gliding exercises.
If the symptoms do not improve, get worse (muscle weakness, muscle wasting) or last longer than 3 months, decompression surgery is needed. Several surgical methods can be used (cubital tunnel release, anterior transposition of the ulnar nerve, medial epicondylectomy).
What can you do yourself to ease the symptoms?
- Avoid activities that keep your elbow bent for a long time.
- If you use a computer often, make sure your chair is not too low.
- Avoid leaning on your elbow or putting pressure on the inner side of your arm. For example, do not drive a car with your arm resting on the car window.
- Keep your elbow straight when you sleep. You can wrap a towel around it to keep it straight, or wear an elbow splint.
Which doctors can treat ulnar nerve entrapment?
Many nerve injuries and disorders are first found and treated by neurologists, neuromuscular specialists, orthopedic doctors or physical therapists. If surgery is needed, it is usually done by a neurosurgeon who specializes in peripheral nerve surgery.
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