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Ulnar Nerve Compression at the Wrist (Guyon’s Canal)
Numbness in your little and ring fingers, or weakness when you grip or pinch? Compression of the ulnar nerve is one possible cause. This page explains ulnar nerve compression at the wrist, in a passage called Guyon’s canal, how it differs from compression at the elbow, and the options for managing it.
What is it?
The ulnar nerve runs down the inner side of the arm, behind the elbow and into the hand on the little finger side. It supplies feeling to the little finger and half of the ring finger, and it controls many of the small muscles in the hand that are used for fine movements, pinch and grip.
The nerve can be squeezed in two main places. The most common is at the elbow, known as cubital tunnel syndrome. Less commonly, it is squeezed at the wrist as it passes through Guyon’s canal, a narrow tunnel on the palm side of the wrist near the base of the little finger.
At a glance
What is it?
Pressure on the ulnar nerve as it passes through Guyon's canal at the wrist
Common symptoms
Numbness or tingling in the little and ring fingers, and weakness or clumsiness of the hand
Who it affects
Less common than compression at the elbow. Can follow repeated pressure on the heel of the hand, such as from cycling
Is it serious?
Not dangerous, but ongoing pressure can lead to lasting weakness and thinning of the hand muscles
Treatment options
Avoiding pressure on the palm, splinting, treating the cause, or surgery
First step
A consultation and nerve conduction studies to assess where the nerve is compressed and how severely
Causes and risk factors
- A ganglion cyst or other lump inside Guyon's canal
- Repeated or prolonged pressure on the heel of the hand, for example from cycling or using tools
- A fracture of the hook of the hamate bone or another wrist injury
- Rheumatoid arthritis or other inflammatory conditions
- Blood vessel problems near the wrist, such as a clot in the ulnar artery
- Extra or unusually placed muscles near the wrist
- In some people, no cause is found
In some people no clear cause is found. Because a cyst, lump or old injury is a common cause of compression at the wrist, investigations often look for a structural cause before treatment is planned.
Symptoms and how ulnar nerve compression presents
Symptoms depend on which part of the nerve is squeezed inside Guyon’s canal. Some people mainly notice numbness or tingling in the little finger and the little finger side of the ring finger. Others mainly notice weakness, such as difficulty with fine tasks, pinching, crossing the fingers or opening jars, sometimes with little or no numbness.
Over time, the small muscles of the hand can become thinner, particularly in the web space between the thumb and index finger. Unlike compression at the elbow, compression at the wrist does not usually cause numbness on the back of the hand on the little finger side.
How is ulnar nerve compression diagnosed?
Ulnar nerve compression is diagnosed from your history and a hand examination. Dr Tomlinson will ask about your symptoms, check the feeling in your fingers and test the strength of the small muscles of your hand. She will also examine your elbow and neck, because pressure on the nerve higher up can cause similar symptoms.
A nerve conduction study (a test that measures how well signals travel along the nerve) can help show where the nerve is compressed and how severely. An ultrasound or MRI scan may be arranged to look for a cyst or other lump, and an X-ray or CT scan may be used if a bone injury is suspected.
Treatment options for ulnar nerve compression
Treatment depends on the cause and on how severe your symptoms are.
If symptoms are mild and there is no lump or injury pressing on the nerve, treatment usually starts with avoiding pressure on the heel of the hand, changing how you grip tools or handlebars, using padded gloves, and sometimes wearing a splint.
Surgery may be recommended if a cyst or other structural cause is found, if symptoms do not improve, or if there is weakness or muscle thinning. Guyon’s canal release opens the canal to take pressure off the nerve, and a cyst or lump pressing on the nerve can be removed at the same time.
When to see a hand surgeon
See a hand surgeon if you have ongoing numbness or tingling in your little and ring fingers, if your hand feels weak or clumsy, or if you notice thinning of the muscles in your hand. Seek earlier review if your symptoms started after a wrist injury or if you can feel a lump near the base of your palm. Earlier assessment gives more treatment options and reduces the risk of lasting nerve damage.
What to expect at your appointment
Our intake form asks you specific questions about your symptoms and how they affect your hand function.
At your first appointment, Dr Tomlinson will take a history of your symptoms and examine your hand, wrist and elbow. She may refer you for nerve conduction studies or imaging if these are needed and have not already been done. Together you will discuss the likely cause and go through the treatment options that suit your situation, so you can make an informed decision about what to do next.
Related conditions and treatments
Ulnar nerve compression at the wrist is less common than compression at the elbow, called cubital tunnel syndrome. Both can cause numbness in the ring and little fingers, so a careful examination is needed to work out where the nerve is squeezed. Numbness in the thumb, index and middle fingers is more likely to be carpal tunnel syndrome. The same nerve can also be compressed higher up, at the elbow, where the condition is called cubital tunnel syndrome. It is possible to have more than one nerve compression at the same time.