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Ulnar neuropathy is an irritation or compression affecting the ulnar nerve. 

The Anatomy

The ulnar nerve stretches through a significant portion of our body. It forms the following path:

  • comes out of the neck
  • runs down the inner aspect of the arm
  • runs around the elbow through a tunnel called the cubital tunnel
  • runs down the forearm
  • enters the hand on the palm and little finger side, through a tunnel called Guyon’s canal

This lengthy nerve supplies sensation to the little finger and half of the ring finger, as well as muscle power to the hyperthenar muscles (muscles at the base of the little finger). 

The nerve also supplies motor power to the intrinsic muscles, which are the tiny muscles in between the metacarpal bones and the hand; these allow the fingers to flex at the knuckles (mcp joints), to squeeze together (i.e. adduct) and spread apart (i.e. abduct). These muscles also contribute to the fine motor skills of the hand.

The Condition

When irritated, the ulnar nerve is most commonly affected at the elbow, where it goes around the corner on the inner (medial side) of the arm, through a groove known as the cubital tunnel.

Normally, with flexion of the elbow, there is some traction and stretching of the ulnar nerve at the elbow. Even when flexing, the ulnar nerve is held in place by a band of tissue called the retinaculum

However, if this tissue is tight or if there is scar tissue, the ulnar nerve may become compressed or stretched beyond its 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 – may also produce pressure on the ulnar nerve in the cubital tunnel.

The Symptoms

Symptoms of ulnar neuropathy include:

  • pain at the elbow, forearm or hand
  • numbness or tingling over the ulnar distribution of the hand (i.e. the little finger and part of the ring finger and hyperthenar eminence)
  • wasting of the hyperthenar muscles and intrinsic muscles (which produces decreased grip strength and difficulty performing fine motor skills with the hand)
  • a claw-like deformity of the fingers may develop in severe cases due to intrinsic weakness. 

The Diagnosis

The diagnosis process may consist of a combination of the following:

  • obtaining a patient history that features some of the above symptoms
  • 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 of the elbow to see if a tingling sensation is produced; this test result is called a positive Tinel sign
  • numbness or nerve irritation of the arm with elbow flexion, produced via the elbow flexion test
  • electrodiagnostic tests such as nerve conduction velocities (NCV) and electromyography (EMG) can be used to determine how severe neuropathy is. (During the nerve conduction velocity tests, test electrodes are applied to the skin and muscles in the upper extremity. 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.)

The Treatment

Treatment of ulnar neuropathy depends on the severity of nerve involvement. 

Mild cases may respond to repetitive elbow flexion exercises, anti-inflammatories, and a silicone elbow padded sleeve.

More severe involvement of the ulnar nerve, however, may require surgery. The specific surgery 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 (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 also slightly lengthened in order to avoid any pressure on the nerve. 
  • If there are spurs from arthritis, or any extra muscle or ganglion cyst tissue, 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. 

The Recovery

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 also started on therapy immediately to maintain and/or rebuild an active assisted range of motion. During therapy, the patient and therapist will move the recently operated elbow with the opposite good arm. Good motion of the elbow is sought to avoid stiffness and motion of the nerve (to avoid the growth of scar tissue), but no force is ever put on the recently reattached muscles. This continues for 6 weeks. 

There is a dressing placed over the incision for the first two weeks post-op, after which the sutures are removed and the patient may shower normally. 

At 6 weeks after surgery, the muscle repair is healed and more aggressive therapy and strengthening exercises are begun. The splint is discontinued as well. 

When a range of motion has been restored to the elbow and strength is good, therapy is discontinued. There is no use allowed of the affected arm for lifting, carrying or driving during the first 6 weeks.

The Results

Usually, ulnar nerve pain will improve quickly after surgery. The normal sensation of the nerve may return right away or take several months to recover; the nerve regenerates at the rate of about 1 inch per month. 

The muscle atrophy and weakness may take many months to correct itself, and may not return in severe cases. As a result, additional surgeries to correct fixed claw finger deformities and to compensate for intrinsic muscle weakness in severe or neglected cases may be necessary.

The Risks

Risks from surgery include the normal anesthesia-related risks, wound healing problems or infection, numbness or irritation around the incision site on the elbow, and the failure of all the sensation or muscle strength to recover.

The Similar Health Problem

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. In these cases, the band of tissue (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 subluxation.

The symptoms of this condition, known as ulnar nerve subluxation, are similar to general ulnar neuropathy. 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 of this condition is done by obtaining a history of ulnar neuropathy symptoms as well as a history of popping or snapping at the elbow. The examination process is the same as above, but also involves seeing or feeling the ulnar nerve pop 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.