Carpal Tunnel Syndrome
Making the Right Diagnosis
By Barbara Headley and Gordon M. Singer
If you want to see the impact of carpal tunnel syndrome (CTS) on our workforce, enter a grocery store and observe the check-out clerks. Wrist braces are common, and lay people have become experts in identifying problem hand symptoms.
Contrary to popular opinion, CTS is not new; Ramazzini described it as early as 1717.1 And the workplace is still associated with repetitive motion, awkward positions and forceful grip.1-2 It's only recently, however, that the incidence of CTS has skyrocketed. Between 1989 and 1995, for instance, incidences of it have increased 45 percent. CTS represents a subcategory of cumulative trauma disorder (CTD), which accounted for 56 percent of all workplace illnesses from 1982 to 1993.3
While CTS is a distinct entrapment syndrome, its symptoms--which occur at various chronic and severity levels--also may indicate other problems, such as tendinitis, thoracic outlet syndrome or myofascial pain syndrome. Criteria for diagnosing CTS include certain symptoms of paresthesia, hypoesthesia, and pain or numbness affecting at least part of the median nerve distribution of the hand. But therapists must look for one or more of these physical findings: Tinel sign; Phalen sign; a decreased/absent sensation to pin prick in the median nerve distribution of the hand; or electrodiagnostic findings of median nerve dysfunction across the carpal tunnel.4-5
In addition to assessing symptoms, physicians and therapists need to carefully determine pain generators. Targeting the cause of pain can lead to an effective, proper diagnosis and treatment planning. Treatment also depends on determining appropriate treatment levels.6
When presented with an employee reporting the problem as work-related, therapists must explore why he seeks treatment. Have his job tasks changed? Is that change responsible for the symptoms? How has that change altered the mechanical and physiological demands placed on joints, muscles and other soft tissue?
In older workers, however, symptoms can be related more to aging and the accompanying postural changes than to alterations of job demands. Postural factors and soft tissue stress, in fact, have been implicated in upper-extremity symptoms, including those that mimic CTS.7-10
People may have past injuries that manifest as symptoms at work, even though the job remains the same. Physical changes can present new stress due to secondary compensation, adaptive movement patterns or changes in postural and fascial alignment and mechanics.
These mechanical changes have been called the "double-crush syndrome," in which pressure is felt on the nerve in two places.11 Multiple sites of compression along the median nerve--a variation of the double-crush--have also been described.4-5
With the double-crush syndrome, changes may result from gradual loss of scapular stabilization, a forward head or elevated, rounded shoulders. These changes alter the forces on soft tissue, while muscles and fascia impose new stress on nerves and blood vessels, creating an entrapment or adhesion that would otherwise rarely be present.11-12
The double-crush phenomenon may be responsible for patients having continued symptoms after surgery. Consider the case of a 34-year-old woman, who was evaluated eight months post carpal tunnel surgery. Although her distal symptoms had decreased, proximal symptoms remained. Rotator cuff pathology was considered the cause of the proximal symptoms--as revealed by an MRI--and another surgery was recommended, but never performed.
A second evaluation revealed significant proximal muscle dysfunction, and the patient began receiving nonsurgical treatment. At the time, proximal symptoms were thought to be related to movement dysfunction and myofascial pain syndrome. While some symptoms resolved with the first surgery, all did not.
As a result, a movement adaptation syndrome (MAS)--movement dysfunction that perpetuates symptoms secondary to adaptive movement patterns--was considered. The woman in this case study also had MAS. Myofascial trigger points--a prime factor in MAS development--results in muscle overload and soft tissue length/tension changes.
Certain trigger points, in fact, may create symptoms remarkably similar to those of CTS. When trigger points are present, they indicate not only referred pain, but muscle/movement dysfunction, which may be significant clues that can lead to CTS.
Therapists should not overestimate the impact of myofascial trigger points on distal symptoms. Patients who are convinced they have CTS and insist on surgery often experience total relief from proximal trigger point treatment. This 34-year-old patient was considered totally healed, although her work chores restrict overhead lifting.
When determining treatment needs, clinicians shouldn't overlook the overlap of CTS symptoms with those due to proximal and distal factors. For example, some refer to entrapment of the neck area by scalenes as a double-crush injury. The minor serial impingement along a peripheral nerve could affect, contribute or result in a distal entrapment neuropathy, through altered axoplasmic flow.
Butler also suggests that losing normal mechanics of the nervous system may result in abnormal axoplasmic flow--a type of "friction fibrosis" along fascial planes.13 Change in the fascial planes, reducing "play" of tissue, is a major factor to soft tissue pain syndromes and may play a role in reducing neural gliding preceding nerve compression.14 When 1,000 surgical cases of CTS were examined, attesting to the normal mechanical loss, 32 percent had bilateral CTS. In addition, cervical arthritis was common in the bilateral cases.15
Treating one area may affect distant symptoms, or other specific interventions may be indicated. For example, addressing the entrapment in the neck region often leads to significant changes in distal findings. A "reverse-crush" has also been described, in which the initial problem is distal, followed by more proximal symptoms.13
Traditional CTS treatment emphasizes changing soft tissue in the carpal tunnel space. Physical or occupational therapy is not always considered the treatment of choice if the diagnosis is considered clear-cut. Some surgeons believe that if they can prove it's a local compression of the medial nerve, then surgery is the only option. But with new attention to neural and fascial tissue constraints, therapists can alter the influence of distant tissue affecting the carpal tunnel space. Therapists can also perform direct mobilization of the carpal tunnel.16
Attention to the neural and fascial planes can contribute to a positive outcome in conservative management. In addition, new electrotherapy tools and laser technology may provide even stronger conservative interventions.
What's more, assessment devices such as surface electromyography (sEMG) can help clinicians problem-solve. With sEMG, therapists can evaluate muscle dysfunction in the scapular stabilizers, the scalene, SCM and forearm muscles, which helps identify dysfunction and myofascial components affecting symptoms.
In the same case study of the 34-year-old woman, forearm muscle dysfunction was also present.
Using multiple channels of sEMG and dynamic movement analysis provides information on muscle dysfunction that may contribute to CTS-like symptoms.17 In addition, sEMG spectral analysis helps therapists assess the fatigue resistance in muscles, which is essential for proper biomechanical positioning.
Inhibition of these muscles from localized muscle fatigue or central drive inhibition provide critical insights into their ability to continue working for long durations under constant low load, repetitive or static, physical demands.
Rapid muscle fatigue can be demonstrated by rapid changes in the median frequency value of the power spectrum during a static contraction.
In addition to using sEMG for treatment problem-solving, assessing physiological risk factors at worksites can reduce the number of claims filed, as well as the cost of claims that are filed. sEMG can be a valuable tool in identifying risk factors related to movement efficiency, static work levels on muscle groups, fatigue and recovery.17
References available upon request.
Barbara J. Headley, MS, PT, is president of Innovative Systems for Rehabilitation Inc., Boulder, CO. Gordon M. Singer, MD, is on staff at Denver Orthopedic Specialists and is board-eligible in orthopedic surgery.