What is Cubital Tunnel Syndrome?
Cubital tunnel syndrome, also known as ulnar nerve entrapment, occurs when the ulnar nerve becomes compressed along the cubital tunnel causing it to become inflamed, swollen and irritated.
The cubital tunnel is located on the inside aspect (medial) of your elbow joint, just behind the bony bump known as the medial epicondyle. The ulnar nerve runs through it as it passes from your upper arm into your forearm to supply the muscles in your forearm and hand. The ulnar nerve is very superficial (close to the surface of the skin) at the cubital tunnel so it is easily knocked causing an electric shock feeling down your forearm. This area is what is referred to as the "funny bone".
What causes Cubital Tunnel Syndrome?
There are many factors that may contribute to or cause cubital tunnel syndrome including:
- Repetitive motion - The ulnar nerve is especially vulnerable to compression at the elbow as it travels through the cubital tunnel. Repetitive or prolonged activities that require the elbow to be bent or flexed can lead to developing the condition. In some cases, an unstable nerve may partially (sublux) or completely displaces out of the tunnel during elbow flexion compressing and irritating it in the process.
- Prior elbow injury or arthritis - Arthritis of the elbow joint can lead to bone spurs in or around the cubital tunnel.
- Diabetes mellitus - Having high blood sugar levels is a risk factor of developing neuropathy (damage to nerves).
- Smoking - Cigarette smoking damages tissue around nerves making them more susceptible to injury.
- Cysts near the elbow joint or arising from the elbow can cause direct compression of the ulnar nerve in the cubital tunnel.
- Obesity - Being overweight increases pressure on joints which puts added stress on tendons, ligaments and nerves.
What are the symptoms of Cubital Tunnel Syndrome?
When people have cubital tunnel syndrome they usually feel pain, tingling or numbness along their inner wrist and/or ring and little fingers. This happens more often when the elbow is bent such as when driving, holding a phone or sleeping (most people sleep with their elbow bent), which would explain why symptoms are worse at night or first thing in the morning.
You may find difficulty with finger coordination (such as typing, or playing an instrument) and weakness of grip strength.
Muscle wasting in the hand can occur if the nerve is compressed or has been compressed for a long time. Muscle wasting cannot be reversed once this occurs. For this reason, it is important to see a doctor if your symptoms are severe or if they are less severe but have been present for more than 6 weeks.
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How Is Cubital Tunnel Syndrome diagnosed?
A diagnosis of cubital tunnel syndrome requires both medical history and physical examination by an experienced physician. A complete neurological exam should include testing for muscle weakness, sensory loss, reflex changes, and other signs of damage to the peripheral nervous system.
A diagnostic ultrasound scan can be used to look at the ulnar nerve in the cubital tunnel. It can see whether it is swollen/inflamed, if it displaces with elbow flexion or if there's a cause for ulnar nerve compression along its course. X-rays may be requested to look for elbow arthritis or other possible causes of ulnar neuropathy.
The most common test used to diagnose cubital tunnel syndrome is a nerve conduction study (NCS), which measures electrical activity along the course of a nerve and the muscles it supplies. NCSs are performed using electrodes placed over specific areas of the body where there is likely to be abnormal function. These tests provide information about whether a nerve or its target muscles are working properly and give clues about possible underlying problems.
Conditions like cervical radiculopathy (nerve irritation in the neck), Pancoast's tumour (a type of lung cancer), and other causes of peripheral neuropathy can mimic cubital tunnel syndrome.
If you believe your symptoms are in keeping with cubital tunnel syndrome make an appointment with an experience physician who can confirm your diagnosis and provide an appropriate management plan.
Treatment options for Cubital Tunnel Syndrome
Cubital tunnel syndrome is treated conservatively initially. For the majority of people, symptoms will settle with rest and activity modification and avoiding provoking elbow positions.
Elbow splint - A splint to stop flexion of the elbow joint is always recommended but some patients may struggle to tolerate this.
Corticosteroid injection - An ultrasound-guided corticosteroid injection around the nerve will reduce inflammation of the nerve and give you excellent pain relief.
Surgical treatment - Reserved for severe cases or those that have not responded to conservative treatment. A simple decompression usually accompanied by an ulnar nerve transposition is performed to prevent the recurrence of symptoms.
