Carpal tunnel syndrome: Keyboards not to blame
April 1, 2007 6 minutes read
Carpal tunnel syndrome: Keyboards not to blame
Research: Typing, repetitive motion not the cause
Employees who come to you complaining of numbness in their wrists caused by their work might not have carpal tunnel syndrome (CTS). But if it is CTS, new research indicates their genes, not their keyboards, are the cause.
Work that involves hours of keyboarding or continuous use of the hands has been the popular target of blame in people who develop CTS, but the evidence is much stronger for genetics than for repetitive hand use, says orthopedic surgeon David Ring, MD, PhD, an assistant professor of orthopedic surgery and a hand and upper extremity surgeon at Massachusetts General Hospital in Boston. In fact, in a review of 117 published studies on CTS, Ring and his colleagues found that while the evidence supporting genetic or inherited risk factors was moderate, the quality and strength of evidence pointing to occupational risk factors was poor.
Though commonly accepted as true, Ring says, the link between hand use and CTS "is overstated, and may be inaccurate." He describes CTS sufferers as "innocent bystanders" whose activities or work likely aren't to blame for the condition.
When CTS became the focus of great attention in the 1980s and 1990s, there developed some misconceptions about what carpal tunnel syndrome is, as well as some misdiagnoses of hand and wrist pain as being CTS. According to Ring, some basics about CTS include:
- CTS is numbness, not pain. The numbness can be so severe that it is painful, Ring explains, but pain without numbness is not CTS.
"[A] common misconception is that patients who present with complaints of activity-related wrist pain have carpal tunnel syndrome," Ring says. "In fact, the hallmark of CTS is numbness that wakes you at night or is present when you wake in the morning."
The typical complaint is of numbness of the thumb, index, and long fingers, and the radial half of the ring finger. Most people sleep with their wrists flexed, which can cause numbness. Shaking the hand gets rid of it, and a wrist splint prevents the numbness because it prevents positioning the wrist in a way that provokes it. Other flexed wrist activities -- driving for instance -- can provoke the numbness.
Symptoms of vague, diffuse activity-related arm pains and little or no numbness are unlikely to be due to carpal tunnel syndrome. Pain-dominant complaints usually represent idiopathic (nonspecific, medically unexplained) arm pains that are strongly tied to psychosocial stressors.
- CTS is slowly but inevitably progressive. Ring points out that unchecked CTS can lead to permanent nerve dysfunction (numbness, atrophy, weakness), so once identified, it will need surgery eventually, although sometimes years or even decades later, to prevent permanent nerve damage.
- CTS is idiopathic. There appears to be genetic predispositions to CTS, but doctors don't know why it occurs.
- Surgery stops the progression of CTS. When the median nerve is released from the carpal tunnel (a solid ring of bones and ligaments at the wrist that the nerve passes through), the numbness and progression of CTS is stopped. Any nerve damage present at the time, however, is likely permanent, though there is a small chance of some recovery, Ring says.
- Other treatments only address symptoms. Surgery is the only thing that affects the course of the disease, explains Ring. Corticosteroids, splints, and other measures only address the symptoms.
Course unknown in most cases
CTS remains poorly understood. While pressure in the carpal tunnel is involved, the cause of the increased pressure is unknown in most patients. In fact, the disease is insidious and symptoms usually begin gradually, although some patients ascribe the problem to a specific injury or event. Initially, symptoms may be felt intermittently, but they may become constant in advanced stages.
Ring's research team evaluated all of the published original data regarding the etiology of CTS (117 studies) according to a quantitative measure of the strength and quality of scientific data for a causal association. Average scores for biological factors such as genetics, race, and age were double those for occupational factors such as repetitive hand use, vibration, etc.
Ring says while these findings may affect future claims of disability, workers' compensation, and personal injury, the evidence of a genetic link should be viewed primarily as reassuring news for people who have CTS.
"There's poor evidence that anything we do or don't do affects the disease process, so we can type, play music, do surgery, etc., to our hearts' content," he insists. "I hope that the main of influence of the evidence that CTS is largely genetic will be to put our minds at ease and free us from guilt and anxiety about our activities."
Grouping CTS in with idiopathic activity-related arm pain is a mistake, he says. Idiopathic hand or arm pain can be caused or aggravated by activity, but, by definition, there is no objective evidence of any injury or disease. On the other hand, CTS is an objectively verifiable, peripheral mononeuropathy.
Whatever happened to CTS?
CTS was first diagnosed more than 100 years ago, but it was viewed by laypeople as almost an epidemic in the 1980s and '90s. Ring says he is hopeful that the misuse of the CTS diagnosis to refer to idiopathic, activity-related pain is subsiding. Sometimes, he points out, a sore arm is just a sore arm.
Our culture accepts the terms "backache" and "headache," which imply disabling pain that does not reflect danger serious pathology, he points out. "We all get headaches and backaches and know that things will turn out fine with rare exception," he says. "Why not accept the idea of an 'armache' and assume that we are healthy, in spite of occasional disabling arm pain, until proved otherwise?"
The leading journalism industry journal, Editor & Publisher, recently asked "Whatever happened to carpal tunnel syndrome?"1 The magazine noted that two decades ago, CTS threatened to cripple newsrooms across the country as journalists were struck by wrist pain and numbness. Ring says the short answer is that the incidence of true CTS has not changed, but misuse of the diagnosis to refer to activity-related arm pain seems to be decreasing.
Occupational health nurses should be aware of the difference between idiopathic, activity-related pain and true CTS, and they should encourage workers complaining of hand or arm pain and numbness to seek appropriate diagnosis. The best treatment for idiopathic arm pain is probably cognitive behavioral therapy based on analogy with other similar illnesses such as back pain and hypochondriasis where there is good scientific support, Ring states.
The evidence of genetic risk factors for CTS have no bearing on treatment, he points out. The treatment of CTS is very straightforward, Ring says. "Activity does not seem to cause the disease or cause any harm," he says. "If the numbness is not controlled with splinting or [electrophysiological testing] shows more than moderate changes, it's time to consider surgery."
The good news for CTS sufferers is that surgery is very successful in those cases, he says. "When we are talking about resolving nighttime/intermittent numbness and preventing progression of nerve damage, surgery is incredibly successful — one of the most predictable surgeries I do," he says. "Surgery for pain is very unpredictable, and it's likely that many of the positive results represent the placebo effect."
Reference
1. Fitzgerald M. Sprain and Pain Wane: Carpal Tunnel Scare Over? Editor & Publisher, Jan. 12, 2007. Available online at www.editorandpublisher.com/eandp/search/article_display.jsp?vnu_content_id=1003531629.
Resource
For more information on carpal tunnel syndrome, contact:
- To read "Quality and strength of evidence supporting occupational risk factors for carpal tunnel syndrome," presented at the American Academy of Orthopaedic Surgeons annual meeting, February 2007, go to www.AAOS.org. Click on "Physician Education," then, at far right, click on "2007 Annual Meeting." Under "Additional Resources," click on "2007 Education," then choose "Podium presentations," "Friday, Feb. 16, 2007," and "361."
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