A Thorough Review of Cubital (Not Carpal!) Tunnel Syndrome
Of the two most common nerve entrapment conditions affecting the arm, the cubital tunnel syndrome is less well-known than the compression neuropathy known as carpal tunnel syndrome. In this article, patients, orthopedic surgeons, and physical therapists will all find valuable information on the cubital tunnel syndrome.
The authors present a detailed review of the surgery done to release the nerve from its confinement in the cubital tunnel. Cubital tunnel syndrome is a lot like carpal tunnel syndrome. Instead of the median nerve being pinched or compressed (the median nerve is affected in carpal tunnel syndrome), it's the ulnar nerve that's affected. Both nerves come down from the cervical spine (neck) to the elbow. The median nerve takes more of a middle of the forearm approach to the wrist, whereas the ulnar nerve travels along the inside of the elbow down to the little finger side of the wrist.
Pressure on the ulnar nerve anywhere along its path from the elbow to the hand can cause numbness and tingling of the last two fingers (ring and little). Ulnar nerve entrapment can also result in hand weakness. Pain is not usually a main symptom with cubital tunnel syndrome. When pain does occur, the patient often reports it occurs along the medial (inside) of the elbow and sometimes down into the forearm.
The condition is called cubital tunnel syndrome because one of the most common places where the ulnar nerve gets pinched is the cubital (elbow) tunnel. This tunnel is just a space made by ligaments, connective tissue, tendons, joint capsule, and bone at the elbow through which the ulnar nerve passes.
The authors place quite an emphasis on understanding the anatomy of the elbow and how it can compress the nerve in one of five places (the cubital tunnel plus four other locations). When treatment is surgical to release restrictions on the nerve, all areas of limitations must be addressed. If the nerve is compressed in more than one area but the surgeon only releases one area, then the symptoms will not be gone -- or they might come back quickly after surgery once the nerve gets irritated again.
How does the physician know you have cubital tunnel syndrome instead of carpal tunnel syndrome? The symptoms affect different parts of the hand and fingers since each nerve supplies different muscles, skin, and tendons. But there are also different clinical tests that can be done to identify which nerve is affected. In the case of cubital tunnel syndrome, tapping, scratching, and pressure tests can be done to provoke the nerve and reproduce the same symptoms.
The physician will carefully examine and test all areas of the elbow looking for the specific cause of the symptoms. The joint will be assessed for any instability and the bones checked for fractures. The condition will be labeled mild, moderate, or severe depending on whether the symptoms are transient (come and go), the severity of weakness, and loss of hand function for activities such as buttoning, typing, or opening doors, bottles, and other containers.
When compression on the nerve has been present a long time, muscle weakness gets worse and deformities of the fingers can start to develop. One of the most recognizable hand deformities from ulnar nerve palsy is a claw hand (also referred to as Duchenne's sign.
Loss of motor control of the muscles to the ring and little fingers results in those fingers getting stuck in a bent position. It's tough to get your hand in pants pockets with the fingers in this position. The longer the paralysis goes on, the more muscles are affected until the patient can no longer grip a key or move the thumb toward the ring and small fingers. This progression of symptoms tells the doctor that the intrinsic (inner) muscles of the fingers have been affected, too.
To confirm the diagnosis and pinpoint the exact area of nerve compression, electrodiagnostic testing can be done. These tests consist of nerve conduction velocity (NCV) and electromyography (EMG). X-rays may be ordered to rule out fractures. A newer test called high-resolution ultrasound is being studied to see if it is a more reliable way to diagnose cubital tunnel syndrome.
Once the diagnosis has been made and confirmed, then it's a matter of identifying the best treatment approach. Sometimes what doctors refer to as benign neglect works for mild cases -- in other words, don't do anything and the problem may eventually correct itself. But most patients aren't willing to test that approach out. They want relief from the annoying symptoms now.
Mild cases of cubital tunnel with symptoms that come and go caused by excessive elbow flexion (usually while curled up sleeping) can be successfully treated using splints to keep the elbows out of bent postures. Physical therapists can help mobilize (move, slide, glide) the nerve within its protective outer covering or sheath. Such neural mobilization techniques can be very successful in alleviating the unpleasant symptoms without surgery.
But when patient education about position and use of the elbow doesn't make a difference, then surgery may be needed. The surgeon has several tools in his/her bag of tricks so-to-speak. Decompression is the first option. The surgeon makes an incision along the nerve near the elbow and releases any tissue holding the nerve down or entangled around the nerve.
Sometimes a simple decompression isn't enough and the surgeon has to transpose or move the nerve away from its original location. In other cases, a muscle is pressing against the nerve every time the muscle contracts. The surgeon moves the muscle instead of moving the nerve. That's called a submuscular or intramuscular transposition. The transposition procedures are much more complex than simple decompression. With muscular transpositions, there is a greater potential for post-operative complications like bleeding, nerve damage with loss of motor function and/or sensation, scar tissue formation, and pain.
If the nerve is being pressed against the bone or the indentation in the bone for the nerve is too shallow, it may be necessary to cut away some of the bone. This procedure is called a medial epicondylectomy. Medial tells us the surgeon is working on the bone along the inside of the elbow. In fact, the surgeon is removing what we often refer to as the funny bone.
As part of the research for this article, the authors reviewed studies published on the outcomes of the different surgical procedures. There really wasn't a difference in results from one procedure to the next. Without evidence of a clear winner, surgeons are advised to do whatever is the simplest and least invasive to correct the problem.
The surgeon must weigh all factors when making a decision about the best surgical approach to take. Sometimes the final decision about what to do and how to do it isn't made until the surgeon can take a look inside at what's going on with the nerve. This decision-making method is called intraoperative assessment. The surgeon checks the nerve's movement; stability; and presence, amount, and location of scar tissue. Every effort is made to avoid complications, problems, and recurrent symptoms requiring additional surgery.
References: Bradley A. Palmer, MD, and Thomas B. Hughes, MD. Cubital Tunnel Syndrome. In The Journal of Hand Surgery. January 2010. Vol. 35A. No. 1. Pp. 153-163.Back