Ulnar tunnel syndrome, also known as Guyon's canal syndrome or Handlebar palsy, is

ulnar neuropathy Ulnar neuropathy is a disorder involving the ulnar nerve. Ulnar neuropathy may be caused by entrapment of the ulnar nerve with resultant numbness and tingling. It may also cause weakness or paralysis of the muscles supplied by the nerve. Ulnar ne ...

at the

wrist In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

where it passes through the ulnar tunnel (Guyon's canal). The most common presentation is a palsy of the deep motor branch of the

ulnar nerve The ulnar nerve is a nerve that runs near the ulna, one of the two long bones in the forearm. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or ...

causing weakness of the

interosseous muscles {{short description, Muscles between certain bones Interossei refer to muscles between certain bones. There are many interossei in a human body. Specific interossei include: On the hands * Dorsal interossei muscles of the hand * Palmar interosse ...

. Ulnar tunnel syndrome is usually caused by a

ganglion cyst A ganglion cyst is a fluid-filled bump associated with a joint or tendon sheath. It most often occurs at the back of the wrist, followed by the front of the wrist. The cause is unknown. The underlying mechanism is believed to involve an out ...

pressing on the ulnar nerve, other causes include traumas to the wrist and repetitive movements, but often the cause is unknown (idiopathic). Long distance bicycle rides are associated with transient alterations in ulnar nerve function. Sensory loss in the ring and small fingers is usually due to ulnar nerve entrapment at the

cubital tunnel The cubital tunnel is a space of the dorsal medial elbow which allows passage of the ulnar nerve around the elbow. Persistent compression of the ulnar nerve in the cubital tunnel is known as cubital tunnel syndrome. Structure The cubital tunnel ...

near the elbow, which is known as cubital tunnel syndrome, although it can uncommonly be due to compression at the wrist.

Causes

Ulnar neuropathy at the wrist is often associated with a mass such as a

thrombosis Thrombosis () is the formation of a Thrombus, blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thrombocytes) and fib ...

or an

aneurysm An aneurysm is an outward :wikt:bulge, bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also b ...

of the

ulnar artery The ulnar artery is the main blood vessel, with oxygenated blood, of the Human Anatomical Terms#Anatomical directions, medial aspects of the forearm. It arises from the brachial artery and terminates in the superficial palmar arch, which joins ...

. The role of activities and exposure is less certain.

Diagnosis

Classification

Ulnar tunnel syndrome may be characterized by the location or zone within the Guyon's canal at which the ulnar nerve is compressed. The nerve divides into a superficial sensory branch and a deeper motor branch in this area. Thus, Guyon's canal can be separated into three zones based on which portion of the ulnar nerve are involved. The resulting syndrome results in either muscle weakness or impaired sensation in the ulnar distribution. Zone 2 type syndromes are most common, while Zone 3 are least common.

Treatment

The role of gloves which help protect the ulnar nerve from compression is unclear. Palsy of the ulnar motor nerve isolated to the wrist is treated with operative decompression, often with concomitant ganglion excision. The surgery is to divide the volar carpal ligament which forms the roof of Guyon's canal, thereby reducing compression on the ulnar nerve.

Causes

Diagnosis

Classification

Treatment

See also

References

Further reading