Ulnar Nerve Palsy is paralysis caused by damage, compression or trapping of the ulnar nerve as it makes its way down the length of the arm. This occurs due to nerve compression at the elbow (cubital tunnel) or at the wrist (Guyon’s canal). Muscle weakness and atrophy predominate the clinical presentation.
The cubital tunnel is in this region commonly referred to as the ‘funny bone’, the area where the ulnar nerve crosses the elbow joint. The wrist is made up of a number of small bones. Two of these bones and their associated ligaments form a canal that runs through the wrist (Guyon’s canal). As the ulnar nerve crosses the wrist, it passes through this canal before it branches to supply some of the fingers in the hand.
Hence depending on the area of affection two clinical syndromes exist:
Cubital Tunnel Syndrome
Cubital Tunnel Syndrome occurs when this area becomes irritated.
Bending of the elbow causes the nerve to stretch several millimetres. Frequent bending of the elbow in activities such as pulling levers, reaching or lifting causes the nerve to become irritated and inflamed.
When the nerve is stretched over the elbow the nerve can sometimes move or actually snap over the medial epicondyle causing irritation.
Leaning on the elbow, resting it on an elbow rest during a long distance drive or running machinery may cause repetitive pressure and irritation on the nerve.
A direct hit on the cubital tunnel may damage the ulnar nerve.
The symptoms of Cubital Tunnel Syndrome primarily involve numbness and tingling in the ring and little finger and the sides and back of the hand. These complaints or symptoms worsen when the elbow is bent i.e when holding a telephone, resting the head on the hand and crossing the arms over the chest. The hand may become weaker resulting in trouble opening bottles or jars. The hand may not perform as well as it did before and there may be a tendency to drop things. Clawing may occur in the ring and little fingers.
Guyon’s Canal Syndrome
Guyon’s Canal is a small tunnel that lies within the wrist (between the Hamate and Pisiform bones of the hand, the roof of the canal is formed by the Volar carpal ligament), it is through this tunnel that the ulnar nerve and artery pass within a neurovascular bundle. The canal is one of the principal sites of ulnar nerve compression.
Guyon’s Canal Syndrome is numbness and tingling in the ring and little fingers caused by irritation of the ulnar nerve as it passes through Guyon’s Canal.
Guyon’s Canal Syndrome arises when there is pressure on the ulnar nerve within the canal.
This pressure can be caused by:
- A cyst within the canal.
- Clotting of the ulnar artery.
- Fracture of the hamate bone.
- Arthritis of the wrist bones.
No matter what the cause of compression of the ulnar nerve, the symptoms are the usually the same.
- Pins and needles in the ring and little fingers.
- A burning pain of the wrist and hand.
- Decreased sensation and clumsiness in the hand.
- In extreme cases, compression of the ulnar nerve at Guyon’s Canal can result in a phenomenon known as Claw Hand.
- In all cases of compression of the ulnar nerve at Guyon’s Canal, sensory supply to the skin of the back of the hand is spared.
- This is because the branch of the nerve that supplies this area (the dorsal cutaneous nerve) leaves the main trunk of the ulnar nerve in the arm before it reaches Guyon’s Canal.
Nonsurgical therapy is composed of elbow or wrist splints to limit mobility in addition to an anti-inflammatory drug such as ibuprofen.
Surgical decompression maybe required in some cases. Cutting of the ulnar nerve may occur following a stab wound or fracture to the arm and suturing of the nerve can retain limited function of the hand.