Guyon’s canal syndrome, also known as Ulnar tunnel syndrome, occurs due to compression of the ulnar nerve as it passes through the wrist. Unlike most nerve compressions, Guyon’s canal syndrome typically involves a cystic structure pressing on the nerve. This cyst is known as a ganglion cyst. It is generally characterized by numbness, tingling, and weakness in the hand, particularly affecting the little finger and ring finger.
The ulnar nerve controls the muscles that move these fingers and provides sensory function to the ring and little fingers. When the ulnar nerve becomes compressed in the Guyon canal, this syndrome develops. The most common cause of Guyon’s canal syndrome is the formation of a ganglion cyst within the canal.
However, repetitive movements, such as cycling, or direct trauma to the wrist causing pressure can also lead to ulnar tunnel syndrome. If left untreated, this condition can result in significant nerve damage. While early diagnosis allows for non-surgical treatments, nerve compression due to a cyst always requires surgical intervention.
What is Guyon’s Canal Syndrome?
Guyon’s canal syndrome is a term used to describe a series of symptoms and findings caused by compression of the ulnar nerve at the wrist. Ulnar nerve compression at the wrist is less common than other types of nerve compressions in the arm and hand. The ulnar nerve travels from the elbow to the hand and passes through a tunnel on the palm side of the wrist, known as Guyon’s canal, which is about 4 cm in length. Compression occurs within this tunnel.
Causes of Ulnar Tunnel Syndrome
After passing through the canal, the ulnar nerve terminates in the little and ring fingers. Guyon’s canal syndrome can develop due to various conditions, such as previous fractures around the wrist, cysts occupying space within the canal, or connective tissue diseases like rheumatoid arthritis. However, in most cases, no specific cause can be identified. It is more common in individuals who perform repetitive wrist movements, such as cyclists. The syndrome typically affects men aged 30-60, though it is also seen in women.
Some of the potential causes of compression include:
- Ganglion cyst
- Fracture or nonunion of the hamate bone
- Ulnar artery thrombosis or aneurysm
- Synovitis (joint lining inflammation)
- Repetitive microtrauma (as seen in cyclists)
- Ulnar-sided wrist instability
Symptoms of Ulnar Tunnel Syndrome
The ulnar nerve divides into superficial and deep branches in Guyon’s canal. The symptoms vary depending on which branch or branches are compressed.
Sensory Loss: Tingling and numbness in the ring and little fingers are common. (In Guyon’s canal syndrome, the back of the hand is not affected, unlike in cubital tunnel syndrome where the ulnar nerve compression also affects the back of the hand.
Weakness: The ulnar nerve transmits motor signals from the brain to many of the muscles that move the hand. In advanced cases of Guyon’s canal syndrome, there is a loss of motor skills, leading to hand muscle weakness and clumsiness. Patients may unknowingly drop objects from their hands. In severe cases, significant weakening and atrophy of the muscle between the thumb and index finger may also be observed.
Diagnosis of Ulnar Tunnel Syndrome
The diagnosis of Guyon’s canal syndrome is clinical, based on the patient’s history and physical examination. The Tinel test is important in diagnosis; during this test, the nerve is tapped over the suspected area of compression. A positive test occurs when the patient feels tingling or an electric shock sensation in the area supplied by the nerve.
Several diagnostic tests can confirm the clinical diagnosis of Guyon’s canal syndrome or help in differential diagnosis. The standard diagnostic test for Guyon’s canal syndrome includes nerve conduction studies and needle electromyography (EMG). These tests measure the electrical conduction of the nerves, helping to determine whether there is any compression and the precise level of compression. Identifying the exact level of compression is important, as ulnar nerve compression is more common at the elbow, which requires different treatment. If a mass compressing the nerve is suspected, MRI imaging may be used.
Treatment of Ulnar Tunnel Syndrome
If the cause of Guyon’s canal syndrome is a ganglion cyst, the only treatment is surgical removal of the cyst. If there is no cyst, non-surgical treatments are initially recommended, including:
Rest: Limiting or avoiding activities that may have caused Guyon’s canal syndrome is the first step in treatment.
Medications: Consult your doctor about using pain relief medications.
Cortisone Injections: Cortisone can be injected into Guyon’s canal under ultrasound guidance to reduce inflammation and swelling in the nerve.
Physical Therapy: Nerve mobilization techniques can be performed by a trained physiotherapist.
Wrist Splints: Splints or braces can be used to keep the wrist in a neutral position, reducing pressure on the nerve.
Differences Between Cubital Tunnel and Ulnar Tunnel Syndrome
Cubital tunnel syndrome presents with symptoms that differ from those of ulnar tunnel syndrome.
Sensory Loss on the Back of the Hand: Cubital tunnel syndrome can cause numbness or sensory loss on the back of the hand (near the little finger), which is not seen in ulnar tunnel syndrome.
Tenderness at the Elbow (Tinel's Sign): In cubital tunnel syndrome, tapping on the inner elbow can cause an electric shock sensation, which is an important diagnostic clue.
Elbow Flexion Test: In cubital tunnel syndrome, bending the elbow (especially for long periods) can worsen numbness and pain, indicating a positive test for cubital tunnel syndrome.
These signs distinguish cubital tunnel syndrome from ulnar tunnel syndrome.
Ultrasound-Guided Cortisone Injection in the Treatment of Ulnar Tunnel Syndrome
Ultrasound-guided cortisone injections are an effective non-surgical treatment for reducing pressure on the nerve and inflammation caused by compression. Ultrasound guidance ensures accurate placement of the injection, targeting the correct area and minimizing side effects.
Advantages of ultrasound-guided injections include:
Precise Targeting: Ultrasound imaging allows for clear visualization of the nerve and surrounding structures, ensuring the injection is delivered to the correct area.
Reduced Risk of Side Effects: The precise targeting minimizes the risk of injecting the wrong area.
Rapid Relief: Corticosteroids can quickly reduce inflammation and provide symptom relief.
Non-Surgical Solution: This treatment can help manage symptoms without surgery, allowing patients to return to their daily activities sooner.
This method is particularly effective for early-stage Guyon’s canal syndrome. However, if symptoms are severe or nerve damage has progressed, surgical treatment may be required.
Surgical Treatment for Ulnar Tunnel Syndrome
Surgical treatment for Guyon’s canal syndrome involves decompressing the ulnar nerve at the wrist by releasing the tissues causing the compression. Surgery is performed through a small 2-3 cm incision on the inside of the wrist under local or general anesthesia.
Immediately after surgery, patients typically experience significant relief from symptoms. Factors affecting the outcome include the patient’s age, duration of symptoms, and severity of pre-operative symptoms. Older patients, particularly those over 65, may experience less improvement in symptoms and hand function. In advanced cases, nerve cells may have died due to prolonged compression. Therefore, early surgery is recommended. However, even patients over 70 years old generally experience significant improvement and are very satisfied with the results. Surgical treatment should not be avoided based on age or disease stage.
