Today's Medical Fact
Eating breakfast helps to burn calories throughout the day.
E. Gene Deune, MD
Johns Hopkins Department of Orthopedic Surgery
Carpal Tunnel Syndrome
By E. Gene Deune, MD
Carpal tunnel syndrome is one of the most common nerve entrapments in the upper extremity. The word “carpal” means wrist in Latin. A syndrome is a diagnosis based on the presence of several symptoms. Thus, carpal tunnel syndrome is a diagnosis based on the presence of the symptoms due to the compression of the median nerve at the region of the wrist known as the carpal tunnel.
The carpal tunnel lies in the wrist. The wrist (carpal) bones form its floor and its two walls. The roof is formed by the transverse carpal ligament, which attaches on the radial side of the wrist (the side closest to the thumb) to the trapezium and the scaphoid bones. On the ulnar side (the side close to the small finger), the transverse carpal ligament attaches to the hamate and the pisiform bones. The transverse carpal ligament serves to maintain the carpal arch, which gives the palm a slightly concave appearance. (Fig. 1) This ligament also serves as a pulley for the finger flexor tendons, allowing the tendons work more effectively during active flexion. Occupying the space within the carpal tunnel are the median nerve and nine flexor tendons to the fingers and thumb. At the level of the wrist, the median nerve is mostly a sensory nerve. It gives off one motor branch, the recurrent median nerve, which innervates the thenar muscles, located on the radial side of the palm, adjacent to the thumb. (Fig. 2) The remaining median nerve branches are the sensory digital nerves to the thumb, index finger, long finger, and the radial side of the ring finger. The ulnar nerve, which passes the wrist through Guyon’s canal and not the carpal tunnel, provides sensation to the small finger and the ulnar side of the ring finger. The radial artery traverses through the wrist outside of the carpal tunnel and terminates in the hand as the feeding artery to the deep palmar arch. The ulnar artery which enters the hand with the ulnar nerve in Guyon’s canal becomes the feeding artery to the superficial palmar arch.
Patients can have varying degrees of numbness or tingling in the thumb, index, long, and the radial side of the ring finger. Patients can also have unexpected electrical shocks that radiate from the wrist to the affected fingers or from the wrist proximally. These symptoms of numbness and tingling may awaken the patient up at night and can be exacerbated if the patient sleeps in the fetal position with wrist flexed or if the patient sleeps on their wrists, which causes compression on the median nerve. During the day, these symptoms may worsen with either extension or flexion postures of the wrist that may occur with driving, typing, holding the phone to the ear, combing the hair, or holding the hair dryer.
Patients can also describe their hands feeling “cold” and think that it’s due to a “lack of circulation”. In response to this, patients will shake their hands to alleviate the discomfort. Some patients will lower their hands to allow gravity to increase circulation to the hands. The physician should perform a vascular examination of the hands and fingers during the evaluation to exclude occlusive vascular diseases as a cause of these symptoms.
Generally, a decrease in hand strength is not noticed as an initial symptom. However, with progression of the carpal tunnel syndrome, the decrease in hand strength becomes more noticeable, due to the compression on the recurrent motor branch. Thenar muscle atrophy can be noted on examination in severe carpal tunnel syndrome.(Fig. 3) If the motor symptom of the decreased hand strength is the predominating symptom, the diagnosis of carpal tunnel syndrome has to be differentiated from the other conditions such as thumb basilar joint arthritis and deQuervain’s tenosynovitis. Radiographs and physical examination can differentiate these two diagnoses from carpal tunnel syndrome. As the carpal tunnel syndrome progresses and is left untreated, there can be a profound decrease in sensation with loss of protective reflexes. The patient may burn or injure their fingers or hands without sensing pain.
Most of the time, the exact cause of carpal tunnel syndrome is unknown. Numerous published papers can be cited to support or to refute any or all potential causes of carpal tunnel syndrome such as occupational factors or repetitive motion activities.[1,2,3,4] Although there is ample evidence to correlate work or repetitive motion as factors in the development of carpal tunnel syndrome, there is to date, no double-blinded randomized prospective study that irrefutably show that work or the type of work a person does causes carpal tunnel the syndrome.
What is known is that anatomically, in idiopathic carpal tunnel syndrome, there is compression of the median nerve within the carpal tunnel usually by the nine flexor tendons and the inflamed tenosynovium. Studies show that the pressure within the carpal tunnel is elevated in patients with carpal tunnel syndrome or those at risk for developing carpal tunnel syndrome. The compression on the median nerve results in a localized region of ischemia, which alters the nerve’s metabolic and physiologic functions, which is perceived by the patient as numbness, tingling, and/or loss of hand strength.
Occasionally, a space-occupying lesion, such as a tumor in the carpal tunnel can cause the compression on the median nerve. The most common tumors are giant cell tumors, lipomas, and ganglion cysts. (Fig. 4) Should a mass be suspected, an MRI should be ordered. Metabolic conditions such as diabetes, thyroid disturbances, and vitamin B6 deficiency can also be causative factors. Progressive wrist arthritis can result in external compression of the carpal tunnel. Trauma to the hand, wrist, or forearm can produce a hematoma within the carpal tunnel, resulting in carpal tunnel syndrome symptoms.
Carpal tunnel syndrome is more common in the 4th to the 6th decades of life. It occurs more often in women than in men.[6,7] Risk factors seem to suggest that diabetes and other metabolic disturbances such as hypothyroidism and vitamin B6 deficiency can also cause carpal tunnel syndrome. Pregnant women can also develop carpal tunnel syndrome during the later months of pregnancy, due to the rapid increase in weight and retention of fluids. Although the carpal tunnel syndrome usually disappears after the pregnancy is over, some studies suggest that these females are at an increased risk of developing carpal tunnel syndrome later in their life.[8,9,10]
When patients are suspected of having carpal tunnel syndrome, a thorough clinical history should be obtained. Many patients will arrive to the physician’s office stating that they have “carpal tunnel syndrome” thinking that hand pain is synonymous with “carpal tunnel syndrome”. A thorough clinical history will alert the physician if there is median nerve compression at the wrist or if there is another cause of hand pain. With early carpal tunnel syndrome, the physical findings may be nonspecific and non-diagnostic, and two-point discrimination in the median nerve innervated fingers may be unaffected. With progression of the carpal tunnel syndrome, there usually is a positive Tinel’s sign and a positive Phalen’s sign of the median nerve at the wrist. A Tinel's sign is when the patient experiences electrical discomfort at the location where the nerve is being tapped by the examiner’s finger. The electrical discomfort can radiate distally or proximally along the nerve’s path. A positive Phalen’s sign is when the patient’s symptoms are reproduced within 60 seconds while the wrist is flexed for 60 seconds. Thenar muscle atrophy can result when the compression is severe and long standing. (Fig. 3)
Nerve conduction velocity measurements (NCV) and electromyography (EMG) are electrical studies that help and can confirm the diagnosis of carpal tunnel syndrome or another peripheral nerve-related compression. Some surgeons feel that the NCV and EMG are not sensitive enough to detect cases of early reversible carpal tunnel syndrome, as the NCV and the EMG will only be abnormal when there has been a significant loss of nerve fibers in the nerve due to the persistent compression.[12,13]
If a tumor or a space-occupying lesion is suspected, imaging studies should be ordered such as a plain radiograph or an MRI. A plain radiograph can sometimes show severe arthritis that is the cause of carpal tunnel syndrome, as it distorts the carpal tunnel. (Fig. 5) Many times, it is non-diagnostic and an MRI is ordered. (Fig. 6)
The initial mode of treatment for carpal tunnel syndrome is aimed at reducing the tenosynovial inflammation and the cause of localized compression of the median nerve at the wrist. If the cause is the improper wrist positioning during typing, sleeping, or driving or other hand activities such as weight lifting, the suggested treatment is the for the patient to wear a prefabricated splint that maintains the wrist in a fixed position, usually at 0 degrees or 10 degrees of extension. These splints are readily available without a prescription in drug stores, pharmacies, or online medical supply distributors. They can also be custom made by the hand therapists. The patients are instructed to wear the splints during the most active times of the day or during the times or the activities that tend to induce the carpal tunnel syndrome symptoms. Patients are also instructed on proper ergonomics for both work and non-work related activities.
Oral anti-inflammatory medications such as ibuprofen are also recommended. If the patient has a vitamin B6 deficiency, oral supplementation with vitamin B6 can be helpful. Generally, the people who are at most risk for vitamin B6 deficiency are those who are taking Isoniazid for treating tuberculosis. Isoniazid reduces systemic vitamin B6 levels resulting in peripheral neuropathy, and patients on isoniazid are instructed to take 50 mg of vitamin B6 once a day. Other medications that may be helpful in resolving the carpal tunnel syndrome symptoms are the medications prescribed for other metabolic conditions such as hypothyroidism or diabetes. Hypothyroidism is thought to increase deposits of mucopolysaccacharides in peripheral nerves and alter the metabolic function of the Schwann cells resulting in peripheral nerve compression and dysfunction. The myxedema seen in hypothyroidism has also been associated with the development of carpal tunnel syndrome.[11,14,15,16,17,18]
A referral to a physical therapist for hand therapy is very helpful in reinforcing the need to optimize ergonomics at both the work place and at home in non-work related activities. In addition to this, the modalities used by the therapists such as hand strengthening exercises, warm wax-baths, and iontophoresis (delivery of medication into a joint or small space via electrical current), can provide significant symptomatic relief to the patients with carpal tunnel syndrome. Generally, the milder the carpal tunnel syndrome is, the better the chances for the symptoms to improve with non-surgical treatments.
Non-surgical treatment is recommended for patients as a first line treatment and for those who are not candidates for surgery because of medical reasons, or pregnant female patients whose symptoms should resolve after the pregnancy.
Some physicians will inject steroids into the carpal tunnel to alleviate the symptoms. There is some disagreement as to whether the injection should be done at all, because the relief of symptoms is often times only temporary and most of the time, it works well only in patients with mild carpal tunnel syndrome cases and not those with moderate to severe symptoms. There is also the possibility of injury to the surrounding skin and tendon and to the median nerve, which can have devastating consequences.[19, 20] Having said this, should the patient not be a candidate for surgery or if surgery has to be delayed, steroid injections become the default treatments along with splinting, therapy, and the use of oral anti-inflammatory medications.
Should the patient’s symptoms persist despite a diligent adherence to the prescribed non-surgical treatment plan, then surgery is indicated to prevent further damage to the median nerve and the muscles that it innervates. The aim of surgery is to relieve the pressure on the median nerve by dividing the transverse carpal ligament, allowing the contents within the carpal tunnel to expand. There are multiple surgical approaches to releasing the carpal tunnel, most of them being variations of two themes: open carpal tunnel release or endoscopic carpal tunnel release or a limited incision, which is a combination of the open and the endoscopic techniques. The reader is directed to other sites to gain more information about the different types of surgery, as each has their opponents and proponents. The controversy surrounding the type of surgery is beyond the scope of this chapter. [21,22]
Elective, non-emergency carpal tunnel release surgery is an outpatient procedure. Carpal tunnel release can be done under local, a regional block, or general anesthesia, depending on the type of release done (open versus endoscopic or limited open incision). The patients are encouraged to actively flex their fingers immediate after surgery and the initial surgical dressing is removed about 4 – 5 days later. For the open release, I generally apply a fiberglass splint on the palmar aspect of the dressing to prevent inadvertent hyperextension or hyperflexion at the wrist to protect the incision. With the endoscopic release, I generally only apply a reinforcing and well padded soft dressing. Most patients do very well with the carpal tunnel release and are back to work within a short time period. Some patients who do not have physically demanding work activities may return in a few days after surgery. Patients who perform strenuous physical labor at their job, usually require three to four weeks to allow for the incision to heal fully. The wound generally reaches 80 – 85% of its ultimate tensile strength at about 21 days after the surgery. During the first month after surgery, the patients are encouraged to lift no more than 5 pounds with their operated hand. After one month, the patients are instructed to increase their weight lifting as tolerated. Patients should notice an immediate difference in sensation, although the more severe the preoperative median nerve compression is, the longer it takes for the nerve to recover. Some patients with severe compression remain with residual numbness and hand weakness despite a complete release.
Should the patient have bilateral carpal tunnel syndrome and both side need surgical decompression, the patient is encouraged to choose the one side that is more symptomatic. Should the patient wish to proceed with bilateral surgical decompression, the patient needs to know that immediate postoperative morbidity will be higher during the first several days after surgery. Some patients are willing to accept this difficulty rather than having two surgeries and two additive times off from work and leisurely activities.
As with any surgery, there are risks to the procedure, including infection, wound healing problems, nerve injury, scar formation and hypersensitive and painful scar, recurrence of the carpal tunnel symptoms, and the need to re-operate. Although rare, major life-threatening consequences can occur. These include cardiac-related events, pulmonary embolism, deep vein thrombosis, stroke, and/or death.
Carpal tunnel syndrome is due to compression of the median nerve at the wrist due to many causes. Treatment includes modification of wrist posture and if the symptoms persist after an initial period with conservative treatment, surgery then becomes the treatment choice. The reader is encouraged to obtain more information about carpal tunnel syndrome at the official websites for the American Association of Hand Surgery and the American Society for the Surgery of the Hand. [23,24]
Figure 1. This is a slice through of a human cadaver wrist showing the median nerve (within the dashed circle) in the carpal tunnel (defined by small arrow points). Occupying the carpal tunnel along with the median nerve are the nine flexor tendons (seen in a gray color to the right of the median nerve). The large arrow points to the transverse carpal ligament.
Figure 2. This picture shows the location of the carpal tunnel in the wrist. The transverse carpal ligament (TCL) forms the roof of the carpal tunnel through which the median nerve (MN) traverses from the forearm into the hand. After it has crossed into the hand, the median nerve splits into the recurrent motor branch (RB), which innervates the thenar muscles, and the sensory branches (Dig N) to the thumb, index finger, long finger, and the radial side of the ring finger.
Figure 3. This patient shows severe advanced carpal tunnel syndrome with thenar muscle atrophy (arrow).
Figure 4. This intraoperative picture shows a large giant cell tumor of the tendon sheath within the distal forearm with extension into the carpal tunnel. The long and larger arrow points to the portion of the giant cell which entered the carpal tunnel causing compression of the median nerve. The thinner and the smaller arrow points to the median nerve, which is being retracted by a retractor in this picture. The patient presented with firmness in the distal forearm and symptoms of carpal tunnel syndrome.
Figure 5. This set of radiograph shows severe wrist arthritis in a pattern known as SLAC wrist (scapholunate advanced collapse), which is usually due to a fracture of the scaphoid bone. This patient had pain from the arthritis and symptoms consistent with carpal tunnel syndrome due to the pressure on the carpal tunnel from the arthritis.
Figure 6. This is an MRI of the wrist. This axial section shows significant inflammation of the tenosynovium of the flexor tendons.