Q & A: CUBITAL TUNNEL SYNDROME (ULNAR NEURITIS)

by Lorenzo G. Walker, M.D.

Surgery of the Hand and Upper Extremity

QUESTION:

Over the past few months, the small and ring fingers of my right hand have begun to feel like they are falling asleep. At times I have pain in my fingers which awakens me at night, and this is somewhat relieved by straightening my elbow. I have also noticed a sensation of weakness in my hand that has caused me to drop things, and a decrease in my power grip. What is causing these problems?

ANSWER:

Cubital tunnel syndrome is caused by compression of the ulnar nerve at the elbow. Have you ever hit the inner part of your elbow and felt an uncomfortable electric-type sensation? Some people call this hitting the "funny bone." In fact, you have not hit a bone at all. You have hit the ulnar nerve, one of three major nerves in the arm. This nerve is located just behind the inner knob of your elbow, and is about the size of a telephone cord. Entrapment of this nerve at the elbow is called cubital tunnel syndrome.

The two functions of the ulnar nerve are to provide sensation to the ring and small fingers of the hand, and to provide nerve impulses which supply the hand with power grip. These two functions are impaired when the nerve gets trapped behind the knob of the elbow, and has difficulty gliding, or when the nerve actually glides too much and comes out from behind the elbow knob, crushing it against the bone. All of these situations result in neuritis, or inflammation of the nerve. Once the nerve is inflamed, it can cause numbness and tingling in the two affected fingers, and progressive weakness of the hand.

QUESTION:

Who gets ulnar neuritis?

ANSWER:

Any patient who uses the elbow to perform repetitive activities can develop symptoms of ulnar neuritis. These symptoms arise as the nerve becomes repeatedly stretched and relaxed, and finds itself pulled tight against the elbow knob, as pictured. Symptoms include night waking due to tingling or numbness in the two affected digits, and pain localized behind the elbow knob, which can radiate to the shoulder or the wrist.

Treatment of cubital tunnel syndrome first involves decreasing the neuritis, or inflammation around the nerve. Anti-inflammatory medications are provided, and the elbow is splinted in extension during the night to prevent the traction which is caused by repetitively flexing the

nerve against the middle elbow knob, or medial epicondyle. If a period of 4-6 weeks of extension splinting fails to relieve these symptoms, a nerve conduction study should be performed. This electrical test is performed by a neurologist, and is very much like testing the flow of electricity in a wire. A small electrode needle is inserted near the nerve above the elbow. A second electrode needle is placed near the nerve below the elbow. A small charge is sent through the upper needle which sends an electrical impulse down the nerve. By timing the interval between the two electrodes, the neurologist learns how long it takes for the signal to get from one point to another. Readings which are below normal indicate that the nerve is damaged and unable to conduct messages at a normal speed.

If nerve conduction studies are positive for cubital tunnel syndrome, or if pain and numbness persist despite splinting, surgical intervention must be considered. In 10-20% of patients, nerve studies are

normal despite significant nerve entrapment. The nerve should therefore be released and placed in a situation where it is not under tension. The procedure that is performed is called a cubital tunnel release, which involves decompressing the nerve behind the inner elbow knob, and shaving a large part of the elbow knob away so that it no longer causes pressure on the irritable nerve. This allows the nerve to freely move up and down with elbow flexion and extension, no longer being constricted by the large hump of bone.

Postoperatively, patients are kept in an elbow splint for approximately ten days. Vigorous therapy is then started to allow the nerve to glide, and to ensure an adequate range of motion. Most patients go back to work between six and ten weeks with the average time lost from work being eight weeks. The scar from a cubital tunnel release is hardly noticeable, as it lies on the inside of the elbow. Occasionally, sensitivity in the scar when the arm is placed at the side will persist for a few months, but this gradually diminishes and eventually is not of concern.

Patients who present with numbness in the hand often present a diagnostic dilemma. It is often difficult for them to remember whether the numbness is predominantly in the thumb, index and middle fingers, or mostly in the ring and small fingers. Numbness in the thumb, index, and middle finger is associated with carpal tunnel syndrome, and is caused by entrapment of the median nerve at the wrist. It is also very common in those who perform repetitive tasks with their upper extremities. Due to the different treatment required by carpal tunnel syndrome and cubital tunnel syndrome, physician evaluation must be precise, including the nerve studies previously mentioned. Occasionally, these two conditions co-exist, and in these cases all five of the fingers are numb from compression of both nerves, one pinches at the wrist and one at the elbow. If these cases do not improve with conservative therapy, a carpal tunnel release and a cubital tunnel release can both be performed under a local/regional anesthetic at the same sitting, and the rehabilitation time for the combined procedure is similar to that for the cubital tunnel release alone.