Michael W Bowman M.D. FACS
Carpal Tunnel Syndrome (compression neuropathy of the Median Nerve) is basically” a pinched nerve in the hand.” The Median Nerve comes out of the neck, goes down the inner aspect of the arm and enters into the hand through a tunnel in the palm between the thumb muscles (thenar muscles) and the muscles to the little finger ( hypothenar muscles). This tunnel, seen in figure 1, is known as the wrist tunnel or Carpal Tunnel. In that tunnel is the median nerve and the 9 flexor tendons (one for the thumb and two for each finger). The Median Nerve supplies sensation to the thumb, index, middle and half of the ring finger. It also supplies muscle function to the thumb or thenar muscles.
Any condition that produces increased pressure in the Carpal Tunnel compresses the Median Nerve, creating symptoms that are known as Carpal Tunnel Syndrome. These symptoms include numbness over the Median Nerve distribution (thumb, index, middle and half of the ring finger), tingling and burning, pain radiating up the arm, weakness of grip and dropping objects. Often the symptoms are worse at night due to a tendency of many people to sleep with the wrist flexed, kinking the nerve further.
Causes of carpal tunnel syndrome are many. Activities or jobs that require repetitive wrist flexion, gripping or finger flexion, have been associated with increased incidence of Carpal Tunnel Syndrome. Trauma such as a wrist fracture may also result in increased pressure in the Carpal Tunnel and symptoms. Medical conditions such as thyroid disease, amyloidosis, rheumatoid arthritis, gout and lupus have also been associated with increased incidence of Carpal Tunnel Syndrome. In rare cases a cyst, abnormal muscle, abnormal artery or tumor may cause Carpal Tunnel Syndrome.
Diagnosis of Carpal Tunnel Syndrome includes obtaining a history that includes some of the above symptoms. There may be a history of pain at night. Tapping over the Median Nerve in the palm may produce tingling or discomfort. This is known as a positive Tinel's Sign. Applying pressure over the Carpal Tunnel may also produce symptoms. This is called the Median Nerve Compression Test. Holding the wrist flexed at 90 degrees for over a minute may also produce numbness or tingling. This is called the Phalen's Test.
In most cases electrodiagnostic tests will be ordered which include nerve conduction velocity tests (NCV) and electromyography (EMG). During the nerve conduction velocity tests, test electrodes are applied to the skin and nerves 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 Carpal Tunnel Syndrome depends on the severity of nerve compression. In mild cases, limiting the aggravating activity may decrease the symptoms. Anti-inflammatories may reduce inflammation inside the Carpal Tunnel. Vitamin B12 has also been shown in several studies to reduce nerve irritation. Wearing a wrist splint at night often helps with the night discomfort by avoiding wrist flexion. Cortisone injections have been shown in several studies to help mild cases of Carpal Tunnel Syndrome. However it has not been shown to work in significant cases of Carpal Tunnel Syndrome. There is also risk of injury to the nerve and there are high rates of recurrence with this technique.
In severe cases of Carpal Tunnel Syndrome and when significant symptoms persist despite conservative treatment, surgery called a Carpal Tunnel Release is indicated. In this surgery the ligament over the top of the Carpal Tunnel, called the Transverse Carpal Ligament, is cut or incised, which increases the diameter of the Carpal Tunnel by approximately 29%. This takes the pressure off the nerve and relieves the symptoms. The skin is then closed. This procedure is performed as an outpatient with local standby or "twilight" anesthesia. A small dressing and splint are applied. The fingers are free and the patient can perform simple activities such as dressing and eating. The hand must remain dry for two weeks while the incision heals. There is no heavy lifting or carrying for two weeks. At two weeks postoperatively, the sutures are removed and the patient may wash the hand. They may then progressively use the hand for heavier activities. They may return to work when comfortable performing activities. This is usually before 6 weeks. Using this standard technique, the complications are very minimal. The possible problems that may occur are complications related to anesthesia, wound healing problems or infection, failure of the sensation to completely return and soreness in the palm known as pillar pain.
There are various” endoscopic" techniques for Carpal Tunnel Release, using one or two incisions. In these techniques an incision is made, a scope is introduced into the Carpal Tunnel and a knife is used to cut the Transverse Carpal Ligament. The theoretical short-term advantages of these techniques are smaller incisions, faster return to work and decreased discomfort in the palm. In no case do the authors of these techniques claim any significant long-term advantage over the standard technique. There are some disadvantages with these techniques. Visualization of the entire Carpal Tunnel and its content are limited. This does not allow the surgeon to address all causes for the Carpal Tunnel Syndrome. Incomplete release of the ligament has been not infrequent. This can result in failure of symptoms to improve or actual worsening and the need for repeat surgery. Injury or lacerations of branches of the median nerve have been noted. All of these above complications from endoscopic Carpal Tunnel Release done elsewhere have been treated by us. Although trained to perform both techniques, I am unwilling to accept the increased surgical risks with endoscopic Carpal Tunnel Release for my patients and perform the time tested standard procedure.