Guyon's canal syndrome is an entrapment of the ulnar nerve as it passes through a tunnel in the wrist called Guyon's canal. This problem is similar to carpal tunnel syndrome but involves a completely different nerve.
The ulnar nerve actually starts at the side of the neck, where the individual nerve roots exit the spine through small openings between the vertebrae. The nerve roots then join together to form three main nerves that travel down the arm to the hand, one of which is the ulnar nerve. After leaving the side of the neck, the ulnar nerve travels through the armpit and down the arm to the hand and fingers. As it crosses the wrist, the ulnar nerve and ulnar artery run through the tunnel known as Guyon's canal. After passing through the canal, the ulnar nerve branches out to supply feeling to the little finger and half the ring finger. Branches of this nerve also supply the small muscles in the palm and the muscle that pulls the thumb toward the palm.
The hamate bone forms one side of Guyon's canal. This bone has a small hook-shaped spur that sticks out to provide an attachment for several wrist ligaments. Known as the hook of the hamate, this small bone can break off and press against the ulnar nerve within Guyon's canal.
Over use of the wrist from heavy gripping, twisting, and repeated wrist and hand motions can cause symptoms. Working with the hand bent down and outward can squeeze the nerve inside Guyon's canal. Constant pressure on the palm of the hand can produce symptoms. This is common in cyclists and weight lifters from the pressure of gripping. Pressure or irritation of the ulnar nerve can cause symptoms of Guyon's canal syndrome.
A traumatic wrist injury may cause swelling and extra pressure on the ulnar nerve within the canal. Arthritis in the wrist bones and joints may eventually irritate and compress the ulnar nerve.
Symptoms usually begin with a feeling of pins and needles in the ring and little fingers, which is often noticed in the early morning when first awakening. This may progress to a burning pain in the wrist and hand followed by decreased sensation in the ring and little fingers. The hand may become clumsy when the muscles controlled by the ulnar nerve become weak. Weakness can affect the small muscles in the palm of the hand and the muscle that pulls the thumb into the palm. Gradual weakness in these muscles makes it hard to spread your fingers and pinch with your thumb. Compression of the ulnar nerve in Guyon's canal syndrome usually causes numbness in the pinky and half of the ring finger.
Activities that might be causing your symptoms need to be changed or stopped if at all possible. Avoid repetitive hand motions, heavy grasping, resting your palm against hard surfaces, and positioning or working with your wrist bent down and out. A wrist brace will sometimes decrease the symptoms in the early stages of Guyon's canal syndrome.
Anti-inflammatory medications such as ibuprofen and aspirin may also help control the symptoms of Guyon's canal syndrome.
Physiotherapy may be suggested to reduce or eliminate the cause of pressure on the ulnar nerve.
If all attempts to control your symptoms fail, surgery may be suggested to reduce the pressure on the ulnar nerve in the form of a Guyon's canal release.