The use of computer keyboards, cell phones, PDA’s, gaming controls, and other handheld devices in our present “Information Age” has been widely claimed in the media to lead to a variety of repetitive stress injuries, including De Quervain’s Syndrome, so-called “Techno Thumb,” and, particularly, carpal tunnel syndrome.
Despite these claims, however, studies performed on this cause-and-effect relationship in recent years have produced no conclusive evidence attributing carpal tunnel syndrome to overuse or incorrect usage of these devices. Carpal tunnel syndrome develops over many years by a gradual reduction in the space within the carpal tunnel for the median nerve. Although there has not been a direct causative link between repetitive use and carpal tunnel syndrome, wrist position (flexion or extension) can increase pressure on the median nerve and either cause symptoms or make them worse.
In order to dispel the myths and rumors attached to the causes, diagnoses, and potential treatment options of the condition, it’s important to understand exactly what it is. We recently sat down with Aaron Daluiski, MD, Assistant Attending Orthopedic Surgeon at Hospital for Special Surgery, to gather his views and clarify the recent misunderstandings about carpal tunnel syndrome.
Carpal tunnel syndrome (CTS) is a compression neuropathy (disease of the nervous system) caused by an increase in pressure on the median nerve. The carpal tunnel is a space in the wrist bound on three sides by bone and covered with a ligament through which nine tendons and one nerve (the median nerve) travel to the fingers. This nerve supplies sensation to the thumb, index, middle, and half of the ring finger (excluding the pinky), while providing innervation of muscles that control thumb motion.
When the median nerve is compressed, it results in increased sensitivity, tingling, pain, weakness, or numbness in the fingers, hand, and wrist; the pinky finger remains largely unaffected. Night symptoms of numbness and/or pain are common in those suffering from this condition. In addition, it is not uncommon for many to experience symptoms bilaterally (on both sides of the body).
The predisposing factors that cause median nerve compression and carpal tunnel syndrome are unknown. Most experts believe that the condition is made worse by prolonged wrist positioning (either flexion or extension), trauma (such as fractures of the wrist or hematoma formation in the carpal tunnel), osteoarthritis, forms of inflammatory arthritis such as rheumatoid arthritis, or inflammation of tendons (tendonitis) in the wrist. There is a higher incidence of carpal tunnel syndrome in patients with diabetes or thyroid disease as well as patients who are pregnant or on hemodialysis.
Activities such as bicycling, gymnastics, or playing tennis require the participant to place pressure directly over the region of the wrist, which may lead to compression of the median nerve and the symptoms of carpal tunnel syndrome.
Despite popular belief, heavy usage of computer keyboards has never been proven to be a direct cause of CTS. In addition, not all wrist pain is CTS. Using an incorrectly-positioned computer keyboard or mouse is linked to certain kinds of wrist pain; Laptop keyboards, especially, are frequently either too small or incorrectly elevated, resulting in wrist strain. However, the pain associated with the use of computers, while exhibiting similarities to CTS-associated pain, is not necessarily CTS itself. These similar types of pain can usually be corrected – primarily with ergonomically-minded corrections to the workspace and, if necessary, with a wrist splint.
“People naturally associate carpal tunnel syndrome with computer usage, and the media have perpetuated so much fear about it that it’s easy to understand why people make that connection,” notes Dr. Daluiski.
The diagnosis of carpal tunnel syndrome is made primarily by clinical examination and the patient’s history of symptoms. It is important to remember that not all wrist and finger pain is CTS. In addition, not all finger numbness or tingling is CTS. Confirmation of the diagnosis with the use of nerve electrodiagnostic testing is often useful.
Electrodiagnostic testing, made up of nerve conduction and electromyography (EMG) testing, is used to confirm the diagnosis of carpal tunnel syndrome and other nerve disorders. Nerve conduction studies (NCS) evaluate the conduction of electrical signals through the median nerve in the carpal tunnel and into the associated muscles. A conduction block, or slowing of the electrical signal through the nerve as it courses through the carpal tunnel, can be compared to the reduced flow of water through a garden hose that has a kink in it. This reduced flow of electricity results in the altered sensation and muscle weakness associated with this syndrome.
EMG testing studies the muscle itself. By examining how the muscle depolarizes when activated, it can be determined if the nerve input to that specific muscle is working properly. Very subtle loss of muscle function can be determined long before the patient experiences any subjective loss in strength, making this portion of the test very important for detecting early nerve damage.
“Electrodiagnostic testing, especially EMG studies, is important,” Dr. Daluiski explains. “EMG testing is the best measurement for determining if pressure on the median nerve has caused early denervation of the muscles at the base of the thumb. If I see evidence of denervation on the EMG portion of the test, I will usually recommend more aggressive treatment because it is more likely to mean the patient already has a significant degree of irreversible damage to the median nerve.”
Treatment options for those with carpal tunnel syndrome depend upon the severity of each case. Regardless, the main objective is to relieve the pressure within the carpal tunnel. “It all comes down to making more room for the nerve,” explains Dr. Daluiski.
Options range from unproven and controversial theories to tested therapies such as braces, medication, and surgical correction.
Low tech solutions:
While the surgical release of the transverse carpal ligament has risks, most patients have significant relief of pain, numbness, and tingling. If treatment is administered early enough to preserve nerve function, the most obvious improvement in the patient is pain relief -- particularly nighttime pain. “There is often dramatic improvement even the first night after surgery,” notes Dr. Daluiski.
If a carpal tunnel release is performed after significant denervation has led to atrophy of the thumb muscles, the surgery will not improve the loss of muscle strength. Once the muscle is denervated, it is impossible for the nerve to form a new connection to the muscle. While sensation in the hand can sometimes improve following surgery, muscle strength and motor function do not. However, recurrence of CTS symptoms after surgery is rare.
Carpal tunnel syndrome has attracted a sizeable amount of press in recent years, leading many of those with hand and wrist pain to believe that their symptoms are the result of this condition. The use of computers and similar devices has been attributed by the media to be a significant cause of CTS; there is, however, no clinical proof that this is true. Regardless of the cause of their symptoms, those with hand and wrist pain should consult their doctor to determine the nature and severity of their condition.
Unproven treatment theories for CTS abound. Those with the condition should exercise caution by accepting only proven treatments administered by licensed physicians. The proven options for carpal tunnel syndrome treatment range from splints and braces to medications and surgery, and it’s important to know how far your condition has progressed in order to choose the appropriate treatment, thereby preserving your mobility while easing your pain.
Reviewed: 6/22/2009 Published: 10/23/2006
Summary by Mike Elvin