Using Electrodiagnostic Tests to Predict Results of Surgery for Cubital Tunnel Syndrome

Carpal tunnel syndrome (CTS) gets a lot of attention because it affects so many people. But there's a second type of nerve compression problem that deserves some attention too. And that's ulnar nerve compression, also known as cubital tunnel syndrome or CuTS.

Just like carpal tunnel syndrome, cubital tunnel syndrome causes pain, sensations of numbness and tingling, and weakness of the hand. But the areas of the forearm and hand affected are different. The symptoms of cubital tunnel syndrome are very similar to the pain that comes from hitting your funny bone.

When you hit your funny bone, you are actually hitting the ulnar nerve on the inside of the elbow. There, the nerve runs through a passage called the cubital tunnel. When this area becomes irritated from injury or pressure, it can lead to cubital tunnel syndrome.

Numbness on the inside of the hand and in the ring and little fingers is an early sign of cubital tunnel syndrome. The numbness may develop into pain. The numbness is often felt when the elbows are bent for long periods, such as when talking on the phone or while sleeping. The hand and thumb may also become clumsy as the muscles become affected.

Tapping or bumping the nerve in the cubital tunnel (Tinel's test) will cause an electric shock sensation down to the little finger. This is called Tinel's sign. Other diagnostic tests that can be done to confirm cubital tunnel syndrome include electrodiagnostic examination. Nerve conduction tests and electromyography to study muscle function are the two main electrodiagnostic tests used for nerve compression.

Treatment for cubital tunnel syndrome (CuTS) is usually conservative. Antiinflammatory medications, changes in activities, a splint, and physical therapy may be helpful. If symptoms are not improved with nonoperative care, then surgery may be recommended to stop damage to the ulnar nerve.

The goal of surgery is to release the pressure on the ulnar nerve where it passes through the cubital tunnel. One surgical treatment is called ulnar nerve transposition. In this procedure, the surgeon forms a completely new tunnel from the flexor muscles of the forearm. The ulnar nerve is then moved (transposed) out of the cubital tunnel and placed in the new tunnel.

Before doing this type of invasive surgery, it would be helpful if the benefit in terms of decreased pain and improved function could be predicted. In this study, a patient-rated tool called the Patient-rated ulnar elbow evaluation (PRUNE) was used to predict change 18 months after ulnar nerve transposition. Electrodiagnostic tests were also used to measure changes in nerve and muscle function. In this way prognosis for functional recovery could be tested and predicted.

One of the specific goals of this study was to see which aspects of the electrodiagnostic tests are the most predictive of pain during daily activities after surgery. By completing the PRUNE questionnaire patients were rated on pain and other symptoms during dressing, household chores, eating, and self-care (e.g., teeth brushing, face washing). Work and recreational activities are also assessed.

Testing took place before surgery (called the baseline) and again 12 to 18 months after anterior ulnar nerve transposition surgery. Seventy-three (73) patients (52 men and 18 women) were included in the study. Almost everyone had sensory changes before surgery and most (85 per cent) had motor changes (muscle action) affecting the hand.

After surgery, half the group still had abnormal sensation but there were still some improvements. Slightly more than one-third of the group experienced a full return to normal sensation. Motor improvement was also present but still not normal in most of the patients. PRUNE scores were significantly better for everyone.

The women in the group seemed to get the best improvements overall. The authors say this can be partly explained by the women's symptoms and disability being worse than the men's before surgery. There are other factors at play (e.g., severity of nerve damage, length of time between injury and surgery) but were not evaluated in this study.

The value of this study is to show the benefits of electrophysiological testing before surgery. The test results help confirm the diagnosis of cubital tunnel compression syndrome and provide prognostic information about expected recovery.

The surgeon may even be able to use the information to plan the optimal time for the surgery. For example, when there is slowing of nerve signals but not complete loss of signals, then conservative care may be helpful. Likewise, if there are just isolated spots where nerve transmission is slowed, the patient may respond well to nonoperative care and surgery may not be needed.

The authors conclude that electrodiagnostic testing is a useful tool for cubital tunnel compression syndrome. The testing doesn't provide all the answers but certainly contributes helpful information in planning treatment. More study is needed to identify clear cut-off points between what is normal and what is considered "abnormal" electrophysiologic values. This is especially true when trying to decide whether or not to have surgery by predicting recovery and outcomes.

References: Qiyun Shi, MD, MSc, et al. Predictors of Functional Outcome Change 18 Months After Anterior Ulnar Nerve Transposition. In Archives of Physical Medicine and Rehabilitation. February 2012. Vol. 93. No. 2. Pp. 307-312.