Guyon's Canal Syndrome

Guyon’s Canal Syndrome- Ulnar Tunnel Syndrome

The ulnar nerve arises from the medial cord of the brachial plexus. After the ulnar nerve passes through the arm, it runs from the medial epicondyle to the pisiform bone in the wrist in a direct trajectory. Two carpal bones are important in relation to the ulnar nerve in the wrist: the pisiform and the hamate. Both the ulnar nerve and the ulnar artery enter the Guyon’s canal. The Guyon’s canal is approximately 4 cm long. The ulnar nerve enters the wrist medial to the ulnar artery. The Guyon’s canal has one proximal entrance and two distal exits, one superficial and one deep. The Guyon’s canal contains the ulnar nerve with its superficial sensory and deep motor branches. ^th lumbricals. The deep branch of the ulnar nerve also innervates the hypothenar muscles, the adductor pollicis muscle, and the deep head of the flexor pollicis brevis muscle. The superficial branch of the ulnar nerve is mainly sensory. It gives supply to the digital nerves of the 4^th and 5^th fingers and a motor branch to the palmaris brevis muscle. Based on the location of compression in the Guyon’s canal, the affected area of the nerve may be purely motor, purely sensory, or a mixture of motor and sensory. Pain and paresthesia in the ulnar 1 ½ digits or clawing of the 4^th and 5^th fingers can be symptoms. Another symptom can be loss of function of the intrinsics (it normally flexes the MCP and extends the IP joints). In low ulnar nerve injury, the flexor digitorum profundus is working (functional). It flexes the 4^th and 5^th fingers and causes clawing (unopposed by the intrinsic muscles). Ulnar nerve palsy results in paralysis of the intrinsic muscles; test the first dorsal interosseous muscle and check for atrophy. 70% of pinch is lost due to loss of adductor muscles.^th and 5^th fingers and causing clawing of these two fingers. High ulnar nerve palsy has less clawing of the 4^th and 5^th fingers and sensory deficit to dorsum of the hand. In cubital tunnel syndrome (high ulnar nerve involvement) you can also find Tinel’s sign at the elbow and positive elbow flexion test. The dorsal cutaneous branch arises before the Guyon’s canal. If you have high ulnar nerve palsy, there will be sensory deficit on the dorsum of the hand, because that nerve will be affected. If you have a low ulnar nerve palsy, that nerve will not be affected because it already branched out or came off from the ulnar nerve and escaped (sensation on that part of the dorsum of the hand). Nonoperative treatments include activity modification, NSAIDS, and splinting. Surgical treatment includes release of the carpal tunnel .In patients diagnosed with both carpal tunnel and ulnar tunnel syndrome, the Guyon’s canal is adequately decompressed by the release of the carpal tunnel. Local decompression can be done especially if nonoperative treatment fails. Decompression of the ulnar nerve by addressing the cause; success of surgery depends on finding a cause. To determine the cause of compression, explore and release of all three zones in the Guyon’s canal, vascular treatment of ulnar artery thrombosis, hook of hamate excision, decompress ganglion cysts, and release hypothenar muscle origin. All of these things are possible causes that need to be addressed. Tendon transfer can be a treatment in late cases; it will correct claw fingers, restore power pinch, and improve Wartenberg’s sign.

The Froment’s test is positive. When pinching a piece of paper between the thumb and index finger, the thumb IP joint will flex if the adductor pollicis muscle is weak due to ulnar nerve palsy. Symptoms also include weak grasp due to intrinsic weakness, Wartenberg’s Sign, and the Allen’s test. Carpal tunnel view x-rays and CT scans are useful to evaluate hook of the hamate fractures and nonunions. MRI is useful to evaluate ganglion cysts. Ultrasound is useful to check vascular status of the hand and to diagnose ulnar artery thrombosis. EMG and nerve studies are helpful. High or low ulnar nerve injury is a differential diagnosis. In low ulnar nerve injury or compression, the flexor digitorum profundus muscle is working; flexing the 4

The Guyon’s canal contains the ulnar nerve with its superficial sensory and deep motor branches. Ulnar nerve compression neuropathy can occur in the Guyon’s canal. The most common causes include volar ganglion, hook of hamate fracture, repetitive trauma, ulnar artery thrombosis, palmaris brevis muscle hypertrophy, or pisiform fracture or dislocation. Volar ganglion cysts may protrude or grow into the canal, which could compress the ulnar nerve. Hook of hamate fracture can lead to neuropathy of the nerve in the tunnel. Compression and inflammation also can result from repetitive trauma such as using a hammer. Trauma over the hook of hamate, where the superficial branch of the palmar artery lies, leads to vascular insufficiency of the ulnar side of the hand. Ulnar nerve compression may occur as a result of pisiform dislocation or fracture. The Guyon’s canal is bound on the floor by the transverse carpal ligament, on the roof by the volar carpal ligament, on the ulnar border by the pisiform and pisohamate ligament, and on the radial border by the hook of hamate. There are three zones of Guyon’s canal compression. Zone I is located proximal bifurcation of the nerve; it is characterized by mixed motor and sensory symptoms, and it is caused by ganglia and hook of hamate fractures. Zone II is located in the deep motor branch; it is characterized by motor symptoms only, and it is caused by ganglia and hook of hamate fractures. Zone III is located by superficial sensory branch; it is characterized by sensory symptoms only, and it is caused by ulnar artery thrombosis or aneurysm. The deep branch of the ulnar nerve innervates all of the interosseous muscles and the 34d and 4