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10 Articles in Volume 12, Issue #6
Carpal Tunnel Syndrome
Case Studies in New Daily Persistent Headache
Hormone Testing and Replacement in Pain Patients Made Simple
Management of Prenatal Low Back Pain
Managing the Diabetic Patient with Dementia
Myofascial Pain Syndrome: Uncovering the Root Causes
New Tools for Improving Patient-to-Physician Communication in Clinical Practice
Suicide and Suffering In the Elderly: We Must Do Better
Three Cases Highlight the Challenges Of Treating Rheumatoid Arthritis
Understanding the Sources of Morphine

Carpal Tunnel Syndrome

One of the most common pain conditions seen in clinical practice, carpal tunnel syndrome may affect up to 10% of workers. Treatment varies based on the severity of the disorder and ranges from stretching/splinting to surgery.

Carpal tunnel syndrome (CTS) is the clinical presentation of symptomatic dysfunction of the median nerve at the transverse carpal ligament and is the most common mononeuropathy seen in clinical practice. The incidence in the general population has been estimated at approximately one per 1,000 persons, although recent surveys have shown that the prevalence may be up to five times that, with CTS twice as common among women than men.1,2 Other studies have described the prevalence among working populations (as diagnosed by either electrophysiologic or symptomatic testing) to be as high as 10%.The annual medical cost of CTS treatment in the United States has been estimated to be $2 billion with 400,000 to 500,000 carpal tunnel release (CTR) surgeries being performed on an annual basis.4,5 Non-medical costs, including lost productivity and functional impairment, are also significant.

Clinical, Anatomic, and Pathological Features
The carpal tunnel is an inelastic space on the volar aspect of the wrist, which is bounded anteriorly by the transverse carpal ligament—anchored to the bones of the wrist—and dorsally by the carpal bones themselves. In addition to the median nerve, the carpal tunnel contains the finger flexor tendons as they pass from the forearm to the wrist (Figure 1).

Figure: Carpal tunnel anatomyFigure 1: Carpal tunnel anatomy

The sensory representation of the median nerve can be seen in Figure 2. Hand muscles supplied by the median nerve include first and second lumbricals, opponens pollicis, abductor pollicis brevis, and half of the flexor pollicis. These are remembered by the acronym LOAF.

Figure: Sensory representation of carpal tunnel syndromeFigure 2: Sensory representation of carpal tunnel syndrome

Carpel tunnel syndrome symptoms often presents with nocturnal or activity-related paresthesias (tingling, burning, pricking, numbness) caused by transient ischemia of the median nerve resulting in conduction block. In these circumstances, increased volume within the fixed carpal tunnel or external compression puts pressure on the nerve. Typical perineural pressure is generally in the range of 2.5 mmHg in healthy individuals. With exposure to elevated pressure, which may reach 30 to 50 mmHg or more, segmental demyelination and ultimately axonal injury occur in patients with CTS. Typically, sensory symptoms and nerve conduction abnormalities precede motor abnormalities. It is thought that this is related to the higher compression sensitivity of the more thickly myelinated sensory fibers.

Related Links for Patients

Carpal Tunnel Syndrome Overview

Carpal Tunnel Syndrome Symptoms and Diagnosis

Carpal Tunnel Syndrome Treatment

The symptoms of CTS relate primarily to median nerve dysfunction caused by compression in the carpal tunnel. Mechanical wrist and thumb pain caused by weakness surrounding the first metacarpal phalangeal joint may also occur. The typical progression of the neuropathic symptoms of CTS may be highly variable. Some individuals present with intermittent paresthesia and maintain relatively normal motor and electrophysiological function. Others, particularly older patients or those with constitutional illness, may present with profound atrophy and sensory loss with little or no discomfort.

The natural history of CTS appears to vary significantly in individuals. This probably stems from the wide variety of physical and environmental factors in play in different individuals. Reviews of the natural history of CTS have identified different longitudinal courses from long-term stability and spontaneous improvement to progressive deterioration and complete median nerve dysfunction. Hypothyroidism, diabetes, and rheumatoid arthritis are risk factors for CTS as they can increase volume and thus pressure within the carpal canal and are also frequently associated with impaired nerve resiliency. Cases of CTS caused by increased carpal canal pressure related to the hormonal changes and volume expansion of pregnancy generally resolve after delivery.

Sensitivity to nociception also varies significantly among individuals and is likely influenced by genetic and other factors. It is interesting to note that CTS is most often a bilateral disorder. In a series of 131 patients, 59% had bilateral symptoms at presentation. Of those presenting with unilateral symptoms, 66% had electrophysiological abnormalities in the contralateral hand and 73% developed symptoms in the initially asymptomatic hand after a mean interval of 3.2 years.6

Risk Factors
Known risk factors for CTS include anatomy, occupational exposure, genetic predisposition, and systemic causes. Anatomic factors relate primarily to the dimensions of the carpal tunnel in relation to its contents and to the generation of pressure exerted on the median nerve within its confines. Occasionally other anatomic factors may contribute to compression of the nerve including ganglion cysts, lipomas, or other masses. Compression as an immediate or late complication of fracture or scarring may also initiate CTS.

Intrinsic patient characteristics clearly influence the development of CTS and likely determine what degree of environmental exposure, if any, is required. Hakim and colleagues studied the relative risks of CTS in female monozygotic twins, dizygotic twins, and singletons.7 They found heritability to be the strongest determinant of CTS, conferring approximately half of all risk.7

In addition, it is well established that certain individuals, for example those with peripheral nerve myelin protein abnormalities or those with familial amyloid deposition, have an increased risk of the development of nerve dysfunction in response to pressure. In one recent study, individuals with a body mass index (BMI) >29 were 2.5 times as likely as individuals with a BMI <20 to develop CTS.8 Diabetes, neuropathy, rheumatoid arthritis, concurrent cervical radiculopathy, and a number of other disease states also confer a predisposition to the development of CTS. Non-occupational exposures such as crutch use and wheelchair propulsion are also risks.

In a recent meta-analysis, a strict case definition of CTS, which included nerve conduction abnormalities and typical symptoms, was used to evaluate the relationship between various risk factors found in the workplace and the occurrence of CTS. Vibration (odds ratio [OR] 5.40), hand force (OR 4.23), and repetition (OR 2.26) were described as risk factors for development of CTS.9 Combinations of high force, awkward hand positions, repetition, and high levels of vibration may afford the highest occupational risk.10 While typing on a computer keyboard has been demonstrated through ultrasonography to acutely increase median nerve cross-sectional area, the relative contribution of this occupational activity to the development of carpal tunnel syndrome remains controversial.11

History and Physical
The diagnosis of CTS is made when the typical symptoms are combined with physical and/or electrodiagnostic findings. While the diagnosis may be made on a clinical basis alone, surgical outcome is generally correlated with electrodiagnostic abnormalities. Therefore, it is recommended that surgical treatment be considered only for those patients with significant electrodiagnostic abnormalities.

The most frequently presented finding is nocturnal paresthesias. While this logically involves the median nerve distribution, it is common for patients to describe numbness in the entire hand, up the forearm, or other areas outside of the median nerve distribution.

Sensory abnormalities are most objectively documented with methods such as two-point discrimination or measurement with Semmes-Weinstein monofilaments. However, these tests have generally shown poor specificity and poor positive predictive value for electrodiagnostically demonstrated median neuropathy.12 Validated hand diagrams are available and useful in discriminating median nerve from other symptoms.13

Commonly used provocative tests include Phalen’s sign (production of hand paresthesias when the wrist is held in maximal flexion for 60 seconds) and Tinel’s sign (paresthesias induced by percussion over the median nerve at the carpal tunnel). The flick “sign” is the shaking of the hand to relieve paresthesias. It was initially described by Pryse-Phillips in the early 1980s and was said to be very sensitive and specific with a >90% positive predictive value for electrodiagnostic abnormalities.14 However, recent publications have described a low sensitivity of the commonly used tests. The sensitivities of the flick, Tinel, and Phalen signs were 37%, 27%, and 34%, respectively, though these signs were increasingly present with increasing electrodiagnostic severity.15

Figure 3 summarizes the frequency of symptoms and findings from a series of 131 patients with CTS published by Bagatur and Zorer.6

Chart: Frequency of symptoms in patients with carpal tunnel syndromeFigure 3: Frequency of symptoms in patients with carpal tunnel syndrome

Electrodiagnostic Evaluation
Nerve conduction studies (NCS) are highly sensitive and specific in CTS. When a clinical diagnosis of CTS exists, NCS are normal less than 10% of the time.16 If a patient has a clinical diagnosis of CTS and the NCS are negative, the physician should assure that the most sensitive and specific electrodiagnostic tests have been done. If NCS are indeed negative, the physician should consider alternative diagnostic possibilities including tendonitis, arthritis, cervical radiculopathy, or other entities.

Many electrodiagnostic tests have been described and a complete review of these is beyond the scope of this article. However, techniques that involve comparison of median sensory and motor latencies across the carpal tunnel to other ipsilateral nerves are the most sensitive and specific tests. They have the additional advantage of being accurate across a wide range of confounding variables including temperature, age, and the presence of a coexisting peripheral neuropathy. The American Association of Electrodiagnostic Medicine, American Academy of Neurology, and American Academy of Physical Medicine and Rehabilitation published an extensive review of this topic.17 Table 1 summarizes some of the commonly used electrodiagnostic tests for CTS.10

There is controversy about the degree to which electrodiagnostic abnormalities predict response to surgical treatment. In some studies, alternative variables such as general health status, mental health status (ie, job dissatisfaction), alcohol abuse, and the involvement of an attorney have been shown to have a greater influence on outcome.18 In a workers compensation population, those patients with more severe abnormalities (ie, >1 msec prolongation of distal motor latency) had better outcomes than those with less abnormal NCS.19 Physicians should consider these issues as treatment decisions are made.

Imaging Techniques
Some studies have demonstrated the usefulness of magnetic resonance imaging (MRI) and ultrasound neurography in CTS. These tests offer the potential benefits of providing anatomic information (as opposed to the physiological information provided by electrodiagnostic tests) while being performed with less discomfort and potentially less cost than electrodiagnostic tests. However, the place of these tests and the validation of their utility in clinical practice are still evolving. One evidence-based review of neuromuscular ultrasound in the diagnosis of CTS concluded that the measurement of median nerve cross-sectional area was accurate and that it probably added value to electrodiagnostic studies in screening for anatomic abnormalities of the wrist.20

Treatments for CTS can be divided into nonsurgical and surgical categories. In general, patients with more severe, consistent, persistent symptoms including significant sensory deficits, motor weakness, thenar wasting, and significant electrodiagnostic abnormalities are considered surgical candidates. Nonsurgical management is encouraged in patients with milder, intermittent symptoms and findings, or as a temporizing measure in those awaiting surgery.

Table: Summary of nerve conduction techniques

Conservative Management
The success of wrist immobilization with neutral position splinting in the management of CTS has been described in medical literature dating back to 1957.21 Since then, a variety of nonsurgical interventions (ranging from yoga to medications) have been employed. However, many of the studies on the conservative management of CTS lack clear definitions of severity or duration of pre-existing symptoms, sufficient follow-up, and are not conducted in a placebo-controlled manner. Thereby, the quality of medical evidence supporting these various nonsurgical treatments is limited, making devising a cohesive conservative management approach difficult.

In 2002, the Cochrane Neuromuscular Disease Group reviewed 21 trials on 12 different noninvasive treatment methods including ergonomic keyboards, therapeutic ultrasound, splinting, oral medications, vitamins, exercise, yoga, chiropractic care, laser acupuncture, mobilization therapies, and magnet treatments.22 Additional focused reviews were completed by this same group on local steroid injections in 2007 as well as ergonomic equipment and therapeutic ultrasound in 2011.23-25 Despite common use in the treatment and prevention of CTS, there has been very limited evaluation of the effectiveness of ergonomic equipment and positioning.24 Two small studies comparing ergonomic keyboard to regular keyboard use failed to demonstrate any evidence of short- or long-term improvement in symptoms, function, quality of life, or neurophysiologic parameters.24 Additionally, neurodynamic mobilization (a technique by which the median nerve is put on maximal stretch through arm and hand positioning), chiropractic treatments, magnets worn over the carpal tunnel, and laser acupuncture have been examined in small studies and overall showed no benefit.22

Carpal bone mobilization was shown to improve patient-reported symptoms within 3 weeks of treatment. This therapy did not, however, provide any significant improvement in pain scores, hand function, wrist range of motion, or need for subsequent surgery.22 One trial comparing 8 weeks of yoga treatment demonstrated improved pain and Phalen’s sign compared to wrist splinting after 8 weeks of treatment.22

Splinting has been a standard of care for CTS. Available data indicate that nocturnal neutral position braces improve symptoms, hand function, and overall patient-reported improvement with short-term use for up to 4 weeks. It does not appear that full-time use of wrist splints provides any additional benefit over nocturnal use. Neutral positioning, rather than mild extension (20°) is preferred.22

Oral medications have been shown to be of limited benefit. Oral steroid treatment appears to have significant short-term benefit in treating symptoms, but there is equivocal evidence regarding improvement of symptoms after discontinuation of treatment.22 Non-steroidal anti-inflammatory drugs (NSAIDs), vitamin B6, diuretics, and gabapentin have shown no short-term benefit in the treatment of CTS compared to placebo.22,26

Studies on ultrasound for management of CTS have compared highly varied techniques, treatment regimens, and treatment schedules.25 Evidence from limited data suggests that ultrasound may be more effective than placebo for short- and long-term symptom management of CTS symptoms, but does not likely have effect on neurophysiologic parameters.22,25

Steroid Injections
Phalen et al reported the first trial of hydrocortisone injection into the carpal canal in 1957.21 Since then, studies on the effectiveness of local corticosteroid injections for the management of CTS have used differing steroids, doses, injection sites, and baseline severity of symptoms. A review of reports found that local steroid injections do provide clinically significant symptom relief after 2 and 4 weeks compared to placebo, but benefits beyond 4 weeks remain unclear.23 It also remains unclear whether the severity of pre-existing CTS symptoms affects responsiveness. Local steroid injection is more effective than oral steroid in reducing symptoms at 3 months.23 The location of the injection—into the carpal tunnel at the wrist crease versus 4 cm proximal to the wrist crease—has no effect on response. There is no evidence to suggest that one type of steroid (longer acting vs shorter acting) or dose of steroid is superior to any other. Lower-dose and higher-dose injections appear to have similar benefit.23 Two injections, done sequentially, do not appear to provide any additional benefit over a single injection. Severity of symptoms, response to other conservative measures, and risk factors for complications (such as bleeding and infection) should be strongly considered when identifying candidates for this treatment. Providers should also consider that symptom improvement from a local steroid injection is not significantly different than oral NSAIDs combined with neutral wrist splinting after 8 weeks of treatment.23

Surgical Options
CTR is the most common hand surgery preformed in United States, reaching 400,000 to 500,000 cases per year.4 Surgical treatment is generally indicated in those who fail conservative management or present with severe symptomatology. Open carpal tunnel release (OCTR) consists of a longitudinal incision, over the carpal tunnel, on the palmar aspect of the hand. The skin, subcutaneous tissue, palmar aponeurosis, and transverse carpal ligament are dissected and released longitudinally to reduce pressure on the median nerve.27

In 1989, Chow first described an endoscopic carpal tunnel release (ECTR) technique.28 Minimally invasive and endoscopic techniques have since been developed in response to the concern that incisions in the tissues overlying the transverse carpal ligament could result in painful scarring or tethering of underlying flexor tendons.27,29 In endoscopic procedures, the transverse carpal ligament is divided from within the carpal tunnel while the overlying structures are left intact. In theory, this may decrease postoperative morbidity and speed ability to return to work.29

In a meta-analysis of recent surgical studies comparing different CTR techniques, ECTR did not appear to yield any better relief of symptoms than OCTR. However, average return to work was 6 days faster in the ECTR group.29ECTR was found to be more cost-effective overall.30 According to this review, complication rates may be lower in ECTR, but more challenging cases (ie, those with significant joint arthritis or stiffness) are not routinely treated with ECTR, possibly skewing this perception.30 There is no overwhelming evidence pointing to superiority of either technique. At this time, the choice between OCTR and ECTR is guided by patient preference and surgeon experience.29,30

When comparing surgical to nonsurgical treatment outcomes, Verdugo et al reviewed a meta-analysis of four recent randomized controlled trials. The authors concluded that surgery is superior to splinting at relieving CTS symptoms.31The trials did not clarify whether this is true in mild cases of CTS. A 2009 publication by Jarvik et al attempted to clarify outcomes with a parallel-group, randomized controlled trial.32 Patents with CTS diagnosed by electrodiagnostic testing were randomized to surgery or a well-defined conservative treatment paradigm including therapy and ultrasound. Patients in both treatment groups improved over 1 year. At 6 and 12 months, greater numbers of patients in the surgical group had more successful outcomes with greater relief of symptoms and improved hand function.32 However, the magnitude of difference between these groups was small and likely of only moderate clinical significance. This study reported differential outcomes based on severity of motor nerve conduction slowing. Patients with distal median motor latency of <5.0 msec assigned to surgery did not have better outcomes than those with similar motor latency assigned to nonsurgical therapy. Those with distal motor latency ≥5.0 msec improved more than similar patients assigned to nonsurgical therapy.32 These findings hint that more severely affected patients may benefit more from surgical intervention than those with mild electrodiagnostic findings. Of note, 61% of patients assigned to nonsurgical treatment did not require crossover to surgical intervention to relieve symptoms.32

CTS remains a common clinical problem with a large clinical and economic impact. This paper has reviewed the current literature regarding the history, diagnosis, and treatment of CTS that should be considered in the individualized management of this disorder.

Last updated on: May 20, 2015
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Diagnostic Ultrasound in Carpal Tunnel Syndrome: A Helpful Additional Tool
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