Ulnar neuropathy is an irritation or compression affecting the ulnar nerve. The ulnar nerve comes out of the neck, goes down the inner aspect of the arm, around the elbow through a tunnel called the cubital tunnel and down the forearm. It then enters the hand on the palm and little finger side through a tunnel called Guyon`s canal. It supplies sensation to the little finger and half of the ring finger and muscle power to the hyperthenar muscles, muscles at the base of the little finger. It also supplies motor power to the intrinsic muscles, which are the tiny muscles in between the metacarpal bones and the hand which allow the fingers to flex at the knuckles(mcp joints), squeeze together(adduct) and spread apart(abduct) ,as well as contribute to fine motor skills of the hand. See figure 1.
Cubital Tunnel Syndrome
The ulnar nerve is most commonly affected at the elbow, where it goes around the corner on the inner or medial side and a groove known as the cubital tunnel. With flexion of the elbow there is some traction and stretching of the ulnar nerve at the elbow. The ulnar nerve is held in place band of tissue called the retinaculum. If this tissue is tight or if there is scar tissue, the ulnar nerve may become compressed or stretched beyond his tolerance, producing ulnar neuropathy. Other conditions such as arthritis of the underlying elbow joint, an elbow fracture, a ganglion cyst coming from the elbow joint or an abnormal extra anomalous muscle male to produce pressure on the ulnar nerve in the cubital tunnel.
Symptoms of ulnar neuropathy include pain at the elbow, forearm or hand, numbness or tingling over the ulnar distribution of the hand(little finger and part of the ring finger and hyperthenar eminence). There may be wasting of the hyperthenar muscles and intrinsic muscles, producing decreased grip strength and difficulty performing fine motor skills with the hand. In severe cases a clawlike deformity of the fingers may develop due to intrinsic weakness. Diagnosis consists of obtaining a history of some of the above symptoms and a physical exam which notes numbness over the ulnar distribution and/or atrophy or weakness of the hyperthenar muscles or intrinsic muscles. Tapping over the ulnar nerve at the cubital tunnel at the elbow is called a positive Tinel sign. Numbness or nerve irritation of the arm with elbow flexion is called the elbow flexion test. Electrodiagnostic tests such as nerve conduction velocities(NCV) and electromyography(EMG) are used to confirm the diagnosis and to help determine how severe the neuropathy is. During the nerve conduction velocity tests, test electrodes are applied to the skin and muscles in the upper extremity and electricity is applied to test how fast the nerves conduct electricity. In cases of nerve compression the speed of electrical conduction is diminished. During the EMG electricity is applied to stimulate a muscle response. With nerve compression the response of muscle to electricity is diminished.
Treatment of ulnar neuropathy depends on the severity of the nerve involvement. Mild cases may respond to when the patient of repetitive elbow flexion, anti-inflammatories and a silicone elbow padded sleeve. more severe involvement of the ulnar nerve may require surgery. This is usually an anterior submuscular transposition of the ulnar nerve with neuroplasty. In this surgery the band of tissue or retinaculum overlying the ulnar nerve is split, the flexor and pronator muscles which attached to the inner aspect of the elbow are detached and lifted up. The ulnar nerve is moved or transposed to the front or anterior part of the elbow, where it is no longer stretched during flexion. The flexor and pronator muscles are then reattached over top of the ulnar nerve, much like a protective blanket. They are slightly lengthened, in order to avoid any pressure on the nerve. If there are spurs from arthritis, and extra muscle or ganglion cyst, that is removed at the time of surgery. This is an outpatient procedure, performed with either general anesthesia or a nerve block to the upper arm. After surgery the patient is placed in a long-arm protective splint extending from the wrist to above the elbow. This is to protect the muscle repair. The patient is started on therapy immediately to perform active assisted range of motion. In this situation the patient and therapist move the recently operated elbow with the opposite good arm. There is good motion of the elbow to avoid stiffness and motion of the nerve to avoid scar tissue, but no force on the recently reattached muscles. This continues for 6 weeks. There is a dressing over the incision for the first two weeks after which the sutures are removed and the patient may shower. At 6 weeks after surgery the muscle repair is healed and more aggressive therapy and strengthening is begun. The splint is discontinued. When range of motion has been restored to the elbow and strength is good, therapy is discontinued. There is no use of the affected arm for lifting, carrying or driving during the first 6 weeks.
Usually ulnar nerve pain will improve quickly after the surgery. the sensation may return right away or take several months. The nerve regenerates at the rate of about 1 inch per month. The muscle atrophy and weakness may take many months to return and may not return in severe cases. Additional surgeries to correct fixed claw finger deformities and to compensate for intrinsic muscle weakness in severe or neglected cases may be necessary. risks include the normal anesthesia related risks, wound healing problems or infection, numbness or irritation around the incision site on the elbow, failure of all the sensation or muscle strength to recover.
Ulnar Nerve Subluxation
In some cases the ulnar nerve may come out of place from the cubital tunnel at the elbow and sublux (partially come out of place) or totally dislocate to the front of the elbow with repeated elbow motion. The band of tissue or retinaculum which holds the ulnar nerve in place has been stretched out or becomes incompetent. This snapping of the ulnar nerve back and forth over the bony medial epicondyle of the elbow produces irritation of the nerve and ulnar neuropathy. The symptoms are similar to ulnar neuropathy described above. In addition there is a snapping or popping sensation with flexion and extension of the elbow. This may happen with or without history of a previous elbow injury.
Diagnosis is obtaining the history of ulnar neuropathy symptoms as well as a history of popping or snapping at the elbow. Examination is the same as above plus seeing or feeling the ulnar nerve popped back and forth across the elbow with flexion and extension.
Treatment of ulnar nerve subluxation and very mild cases with popping, but no significant numbness or pain may be using a protective silicone elbow sleeve. The next option is surgical treatment. This consists of a anterior submuscular ulnar nerve transposition as noted above. The postoperative course and risks are the same.