What is Guyon Canal Syndrome?
Guyon canal syndrome is an uncommon condition where the ulnar nerve, one of the main nerves in your arm, gets damaged as it passes through a narrow passage in the wrist known as the Guyon canal. The ulnar nerve starts from the spinal cord sections C8-T1 and is part of the brachial plexus, a network of nerves that send signals from your spine to your arm and hand. In the upper arm, the ulnar nerve runs behind and on the inside of the main artery in the arm, heading for the back of the elbow. It goes into a muscle divider, known as the medial intermuscular (IM) septum, at a structure called the arcade of Struthers.
The ulnar nerve then enters a tunnel in the elbow known as the cubital tunnel, located behind a bony bump on the inside of the elbow called the medial epicondyle. From here, it goes into the forearm through between two parts of the flexor carpi ulnaris muscle, a muscle in the forearm that helps to bend the wrist. It finally reaches the hand through the Guyon canal, providing movement and sensation to the fingers. The Guyon canal is a vulnerable spot where the ulnar nerve can be easily compressed or injured. However, it’s more common for ulnar nerve injury to occur at the elbow, in a condition called cubital tunnel syndrome.
The Guyon canal is bordered by these structures:
- The volar carpal ligament, or the “roof” of the canal
- The transverse carpal ligament, or the “floor” of the canal. This ligament continues from the ulnar side of the hand/wrist as the “floor” of the Guyon canal before it transitions to form the “roof” of the carpal tunnel, another tunnel in the wrist.
- The pisiform bone, the pisohamate ligament (a ligament between the pisiform bone and the hamate bone), and the abductor digiti minimi muscle (a muscle that moves the little finger away from the rest of the fingers) make up the ulnar border (the side closer to the little finger)
- The hook of the hamate bone forms the radial boundary (the side closer to the thumb)
What Causes Guyon Canal Syndrome?
Damage to the lower part of your ulnar nerve, a nerve that runs down your arm to your hand, can occur due to a few reasons like being squished, inflamed, injured or due to poor blood flow. Some of the causes include:
* Fluid-filled swelling known as a Ganglion Cyst
* Fracture or displacement of a small bone in the wrist known as the hook of hamate
* Tumors such as lipoma, a benign mass of fatty tissue
* Repeated damage, like from gripping a bicycle handlebar too hard
* Unusual muscle (e.g., abductor digiti minimi) or too much fat tissue within the canal
* Clotting or ballooning of the ulnar artery, a condition known as Hypothenar Hammer Syndrome (HHS)
HHS is a unique way your ulnar nerve can get hurt, originating from blood clotting or ballooning of the ulnar artery. This can lead to inflammation and subsequent squishing of the ulnar nerve at a specific location on your wrist called the Guyon canal. The cause of this issue is very similar to that of Guyon’s canal syndrome where the base of the palm (hypothenar area) is repeatedly harmed and ultimately results in an injury to the ulnar artery.
Some research suggests that 30% to 40% cases of Guyon canal syndrome are due to ganglion cysts. Another research proposes that 45% of the cases arise from unknown causes.
Risk Factors and Frequency for Guyon Canal Syndrome
Guyon canal syndrome is often caused by a type of lump called a ganglion cyst or repetitive injury. However, we don’t know exactly how common this condition is because there hasn’t been enough research to give us clear numbers.
Signs and Symptoms of Guyon Canal Syndrome
Guyon canal syndrome is usually diagnosed based on medical history and symptoms, and it often occurs due to repetitive trauma, like regularly riding a bicycle, or a direct injury to the hand, such as a broken bone. Signs and symptoms may vary depending on where the ulnar nerve is damaged and may affect either muscle control, sensation, or both.
Patients with muscle control issues may suffer from weakness or even paralysis of certain hand muscles, leading to a weakened grip and curling of the fourth and fifth fingers. In severe cases, there might be visible muscle loss in the area just below the smallest finger. To distinguish between Guyon canal syndrome and similar conditions, such as cubital tunnel syndrome, healthcare professionals check the strength of different hand and forearm muscles. A key sign of Guyon canal syndrome is typical sensation on the back of the hand and fingers, which aren’t affected because their nerves bypass the Guyon canal. Another sign, called the Tinel sign, is pain or a tingling sensation when the wrist area is lightly tapped.
Another symptom of Guyon canal syndrome is that patients might struggle to grip paper due to weakness in the thumb muscle known as the adductor pollicis. Clinically, this is assessed by a Froment sign, which means the thumb excessively flexes to compensate for the weakness.
Another key sign is the Wartenberg sign, where the smallest finger appears over-extended compared to the rest of the hand. This happens because of damage to the muscles usually responsible for pinching the fingers together. Moreover, sensation problems will cause pain and/or abnormal sensations along the inner palm and the fourth and fifth fingers.
The Allen Test can be used to help identify any potential issues with the blood flow in the hand, especially when ulnar artery thrombosis, a specific heart condition, is suspected.
The severity and duration of these symptoms can vary. The severity is generally categorized on a scale from 1 to 5, with 1 being very mild and 5 very severe. The symptoms could be acute (less than a month), subacute (two to three months), or chronic (more than three months).
Testing for Guyon Canal Syndrome
If you may have a broken bone (particularly a hamate, one of the small bones in your hand), your doctor may use a hand x-ray or a special type of scan called a computed tomogram (CT) scan to check.
If your doctor needs a more detailed image of the anatomy of your hand and wants to look for anything obstructing the ulnar nerve (one of the three main nerves in your arm), they can use a magnetic resonance imaging (MRI) scan. Things that can push against this nerve and cause problems include small fatty lumps (lipomas), fluid-filled lumps (ganglion cysts), or unusual muscle structures.
Your doctor can check if you have a blockage in your ulnar artery (the main blood vessel in your arm) by using a Doppler ultrasound. This is a type of ultrasound that can show how blood flows through your arteries.
Another way your doctor can check for problems with your ulnar artery, like an enlarged area (aneurysm) or blockage (thrombosis), is with an angiography. This is a test that involves injecting dye into your bloodstream to make your arteries easier to see on an x-ray.
To check how well your nerves are functioning and find out where a nerve might be getting compressed (whether it’s in the wrist, elbow, or near the spine), your doctor can use tests called electromyography (EMG) and nerve conduction velocity (NCV). These tests involve sending tiny electric shocks through your nerves to see how quickly and well they carry signals.
Treatment Options for Guyon Canal Syndrome
The method your doctor decides to treat your injury or condition will depend on how long and severe your symptoms have been, as well as the exact cause of your symptoms. For instance, high-performance athletes and professional baseball players can suffer from a specific type of fracture called “hook of hamate” fractures. These can happen from a single traumatic injury or from repetitive tasks during their sports activities. In these cases, the majority of hand surgeons prefer to perform a specific surgical procedure known as an isolated hook of hamate incision. This specific surgery results in few complications after surgery, allows athletes to return to their sport in about 3 to 4 weeks, and generally results in high satisfaction from patients.
If you’re dealing with a condition called Guyon canal syndrome, the treatment options are quite similar to another condition called carpal tunnel syndrome. Treatment can range from conservative management to surgical decompression. Conservative management involves educating the patient on how to avoid certain actions that could make the condition worse and using a wrist splint. For instance, people, particularly cyclists, should try to avoid repeatedly stressing the canal or compressing it mechanically. Cyclists may need to adjust their bike handlebars to a more comfortable position. It’s also recommended to avoid extending the wrist for long periods because it puts pressure on the ulnar nerve in the hand, which can contribute to Guyon canal syndrome.
A wrist splint should be used to keep your wrist in a neutral position but allow your fingers to move around freely. This splint should be worn at least at night, for a recommended period of one to 12 weeks.
According to a study in the British Medical Journal, a group of medical professionals agreed that conservative management is best for mild to moderate symptoms that have lasted up to three months. For more severe symptoms or if symptoms have been present for three months or longer, surgical decompression is favored. After surgery, there may also be recommended post-surgical exercises, especially if your joint movement is limited. Wearing a splint after surgery isn’t always necessary but may help patients who habitually put strain on their wrist joint.
The same study showed that non-steroidal anti-inflammatory drugs and corticosteroid injections, usual treatments for many types of inflammation and pain, may not be helpful in treating Guyon canal syndrome.
There are also additional treatments such as therapeutic ultrasound and nerve gliding exercises, which can be beneficial.
In the case of ulnar artery thrombosis or an aneurysm (also known as hypothenar hammer syndrome), those who don’t have symptoms don’t usually need surgery. However, in cases where symptoms are present, the patient’s treatment may range from medications that prevent blood clots (antiplatelet drugs) to surgery.
What else can Guyon Canal Syndrome be?
When dealing with medical conditions, it’s important to consider a broad range of possibilities. Here are some conditions that doctors might need to consider:
- Alcohol-related nerve damage
- Amyotrophic lateral sclerosis (a serious neurological condition)
- Brachial plexus abnormalities (issues with the nerve network near the shoulders)
- Cervical disc disease (a problem with the spinal discs in your neck)
- Cervical spondylosis (age-related wear and tear impacting the spinal discs in your neck)
- Epicondylitis (also known as tennis elbow, inflammation of the elbow joint)
- Pancoast tumor (a rare lung cancer that can cause shoulder pain)
- Thoracic outlet syndrome (compression of the blood vessels or nerves near your collarbone)
- Traumatic peripheral nerve lesions (damage to the nerves that link your brain and spinal cord to the rest of your body)
