by Carl Butterfield, M.D., assistant to Dr. Reid
This syndrome is also known as an ulnar nerve entrapment at the wrist. At the wrist, The ulnar nerve enters Guyon's canal along with the ulnar artery, which runs just lateral to the nerve. This canal runs along the lower edge of the palm, on the little finger side of the hand. In the middle of the canal, the ulnar nerve splits into its two terminal branches (deep and superficial) that go on to the palm, ring and little fingers.
Symptoms associated with Guyon's canal syndrome fall into three types depending on the level and type of compression involved. Type I involves compression in the proximal aspect of Guyon's canal. Here, motor weakness in all ulnar innervated hand intrinsics and typical ulnar distribution sensory loss that splits the ring finger are present. The dorsal aspect of the hand may not loose sensation in this type of syndrome. Type II is the most common syndrome type, and results from the compression of the ulnar nerve at the level of the lower wrist. With type II lesions, the sensory branch to the dorsal aspect of the hand and the innervation of the muscles of the base of the palm are spared. Type III is the least common, and involves pure sensory loss from compression of the superficial branch at the distal aspect of Guyon's canal. Therefore, in this type of lesion the symptoms mostly involve loss of sensation or feeling.
Electro-diagnostic studies may be helpful, particularly in distinguishing type I lesions from cubital tunnel syndrome. Motor conduction velocity in the across-the-elbow and the elbow-to-wrist segments should be normal because this region is outside of the canal compression. Prolonged sensory latency should be seen in types I and III. Prolonged distal motor latency and denervation potentials are identified in types I and II lesions, but weakness of the muscles at the base of the palm are spared in type II.
Guyon's canal syndrome can be caused by acute or chronic trauma or by mass lesions (anomalous muscles, arthritic changes, tumors, ganglion cysts, or vascular thrombosis), therefore a complete diagnostic work-up must be done. If the symptoms can be related to specific occupational or recreational activities these need to be addressed in the initial conservative phase. If conservative therapy fails or if significant weakness is present, surgical treatment is indicated. Exposure of the canal can be made through an incision over the base of the palm of the hand. The most common non-traumatic cause of this syndrome is a ganglion, therefore the course of the canal should be inspected for this and any other mass lesions. If no mass is found, resection of any constricting bands and unroofing of the canal is then indicated.
With any type of surgical procedure there are always risks involved. These risks may be very low or infrequent, but because they are possible, they must be taken into consideration when deciding whether or not to have this surgery. The potential risks include; but are not limited to: infection, bleeding, loss of life, paralysis, weakness, numbness, nonrelief, recurrence, pain, poor wound healing, and other serious complications.
The desired benefits to a surgical treatment for Guyon's canal syndrome are related to the surgical indications, and are: (1) Decompression of the ulnar nerve to prevent or minimize permanent nerve damage, (2) to decrease or resolve the problematic symptoms, and (3) to improve strength and sensation in the affected limb.
Recommendations After Surgery:
Immediately after surgery, the patient is advised to keep the arm above the level of the heart. For seven to ten days after the surgery (until the wound is healed), the incision should be kept clean and dry. This is to decrease the chances of developing a post-operative infection. If the bandage should become soiled or wet, it should be removed immediately, and replaced with a clean, dry one. If the bandage needs to be removed, you will find sutures at the incision site. These should not be removed, because their purpose is to hold the skin edges together while the wound heals. The sutures and the bandage will be removed at the first post-operative visit ( which will be in approximately ten days). Also, please remember that if during the time that the wound is healing, you should develop a fever, or if the wound becomes red, inflamed, or starts to drain, the treating physicians office should be contacted promptly.
Pain Management After Surgery:
During the brief time in the hospital, the patient will be provided with either oral or injectable pain medication. As soon as the pain can be controlled with medication by mouth, it is advised that the patient do so, because when at home all pain medication will be by mouth. It is important to remember that pain medication be only taken when needed and only as prescribed to avoid the possibility that the medication loose its ability to control pain adequately, or to become habit-forming.