Background Carpal tunnel syndrome (CTS) is a collection of characteristic symptoms and signs that occurs following compression of the median nerve within the carpal tunnel. Usual symptoms include numbness, paresthesias, and pain in the median nerve distribution. These symptoms may or may not be accompanied by objective changes in sensation and strength of median-innervated structures in the hand. See image below. The hands of an 80-year-old woman with a several-year history of numbness and weakness are shown in this photo. Note severe thenar muscle (abductor pollicis brevis, opponens pollicis) wasting of the right hand, with preservation of hypothenar eminence. Pathophysiology Until the advent of electrophysiologic testing in the 1940s, carpal tunnel syndrome (CTS) commonly was thought to be the result of compression of the brachial plexus by cervical ribs and other structures in the anterior neck region. It is now known that the median nerve is damaged within the rigid confines of the carpal tunnel, initially undergoing demyelination followed by axonal degeneration. Sensory fibers often are affected first, followed by motor fibers. Autonomic nerve fibers carried in the median nerve also may be affected. The cause of the damage is subject to some debate; however, it seems likely that abnormally high carpal tunnel pressures exist in patients with CTS. This pressure causes obstruction to venous outflow, back pressure, edema formation, and ultimately, ischemia in the nerve. The risk of development of CTS appears to be associated, at least in part, with a number of different epidemiologic factors, including genetic, medical, social, vocational, avocational, and demographic. Epidemiology Frequency United States The incidence of carpal tunnel syndrome is 1-3 cases per 1000 subjects per year; prevalence is approximately 50 cases per 1000 subjects in the general population. Incidence may rise as high as 150 cases per 1000 subjects per year, with prevalence rates greater than 500 cases per 1000 subjects in certain high-risk groups. International A paucity of population-based studies of carpal tunnel syndrome (CTS) exists; however, the incidence and prevalence in developed countries seems similar to the United States (eg, incidence in the Netherlands is approximately 2.5 cases per 1000 subjects per year; prevalence in the United Kingdom is 70-160 cases per 1000 subjects).[2, 3, 4] CTS is almost unheard of in some developing countries (eg, among nonwhite South Africans). Mortality/Morbidity Carpal tunnel syndrome is not fatal, but it can lead to complete, irreversible median nerve damage, with consequent severe loss of hand function, if left untreated. Race Whites are probably at highest risk of developing carpal tunnel syndrome (CTS). The syndrome appears to be very rare in some racial groups (eg, nonwhite South Africans).[4] In North America, white US Navy personnel have CTS at a rate 2-3 times that of black personnel.[5] Sex The female-to-male ratio for carpal tunnel syndrome is 3-10:1. Age The peak age range for development of carpal tunnel syndrome (CTS) is 45-60 years. Only 10% of patients with CTS are younger than 31 years. History The patient's history often is more important than the physical examination in making the diagnosis of carpal tunnel syndrome (CTS). Numbness and tingling Among the most common complaints, patients will reveal that their hands fall asleep or that things slip from their fingers without their noticing (loss of grip, dropping things); numbness and tingling also are commonly described. Symptoms are usually intermittent and are associated with certain activities (eg, driving, reading the newspaper, crocheting, painting). Nighttime symptoms that wake the individual are more specific to CTS, especially if the patient relieves symptoms by shaking the hand/wrist. Bilateral CTS is common, although the dominant hand is usually affected first and more severely than the other hand. Complaints should be localized to the palmar aspect of the first to the fourth fingers and the distal palm (ie, the sensory distribution of the median nerve at the wrist). Numbness existing predominantly in the fifth finger or extending to the thenar eminence or dorsum of the hand should suggest other diagnoses. A surprising number of CTS patients are unable to localize their symptoms further (eg, whole hand/arm feeling dead). This generalized numbness may indicate autonomic fiber involvement and does not exclude CTS from the diagnosis. Pain The sensory symptoms above commonly are accompanied by an aching sensation over the ventral aspect of the wrist. This pain can radiate distally to the palm and fingers or, more commonly, extend proximally along the ventral forearm. Pain in the epicondylar region of the elbow, upper arm, shoulder, or neck is more likely to be due to other musculoskeletal diagnoses (eg, epicondylitis) with which CTS commonly is associated. This more proximal pain also should prompt a careful search for other neurologic diagnoses (eg, cervical radiculopathy). Autonomic symptoms Not infrequently, patients report symptoms in the whole hand. Many patients with CTS also complain of a tight or swollen feeling in the hands and/or temperature changes (eg, hands being cold/hot all the time). Many patients also report sensitivity to changes in temperature (particularly cold) and a difference in skin color. In rare cases, there are complaints of changes in sweating. In all likelihood, these symptoms are due to autonomic nerve fiber involvement (the median nerve carries most of the autonomic fibers to the hand). Weakness/clumsiness - Loss of power in the hand (particularly for precision grips involving the thumb) does occur; in practice, however, loss of sensory feedback and pain is often a more important cause of weakness and clumsiness than is loss of motor power per se. Physical Clinical examination is important to rule out other neurologic and musculoskeletal diagnoses; however, the examination often contributes little to the confirmation of the diagnosis of carpal tunnel syndrome (CTS). Sensory examination Abnormalities in sensory modalities may be present on the palmar aspect of the first 3 digits and radial one half of the fourth digit. Semmes-Weinstein monofilament testing or 2-point discrimination may be more sensitive in picking this up; however, in the author's experience, pinprick sensation is as good as any test. Sensory examination is most useful in confirming that areas outside the distal median nerve territory are normal (eg, thenar eminence, hypothenar eminence, dorsum of first web space). Motor examination - Wasting and weakness of the median-innervated hand muscles (LOAF muscles) may be detectable. L - First and second lumbricals O - Opponens pollicis A - Abductor pollicis brevis F - Flexor pollicis brevis Special tests - No good clinical test exists to support the diagnosis of CTS. Hoffmann-Tinel sign Gentle tapping over the median nerve in the carpal tunnel region elicits tingling in the nerve's distribution. This sign still is commonly looked for, despite the low sensitivity and specificity. Phalen sign Tingling in the median nerve distribution is induced by full flexion (or full extension for reverse Phalen) of the wrists for up to 60 seconds This test has 80% specificity but lower sensitivity. The carpal compression test[6] This test involves applying firm pressure directly over the carpal tunnel, usually with the thumbs, for up to 30 seconds to reproduce symptoms. Reports indicate that this test has a sensitivity of up to 89% and a specificity of 96%. Palpatory diagnosis This test involves examining the soft tissues directly overlying the median nerve at the wrist for mechanical restriction. This palpatory test has been noted to have a sensitivity of over 90% and a specificity of 75% or greater. The square wrist sign The ratio of the wrist thickness to the wrist width is greater than 0.7. This test has a modest sensitivity/specificity of 70%. Several other tests have been advocated, but they rarely provide additional information beyond that which the Phalen and square wrist signs provide. Causes Note that carpal tunnel syndrome (CTS) is associated with many different factors.fracture (Colles) Acute, severe flexion/extension injury of wrist Space-occupying lesions within the carpal tunnel (eg, flexor tenosynovitis, ganglions, hemorrhage, aneurysms, anomalous muscles, various tumors, edema) Diabetes Thyroid disorders (usually myxedema) Rheumatoid arthritis and other inflammatory arthritides of the wrist Recent menopause (including post-oophorectomy) Renal dialysis Acromegaly Amyloidosis Vocational/avocational[7, 8, 9] - Activities that may be associated with CTS (particularly in combination) involve the following: Prolonged, severe force through the wrist Prolonged, extreme posture of the wrist High amounts of repetitive movements Exposure to vibration and/or cold Other factors Lack of aerobic exercise Pregnancy and breastfeeding Use of wheelchairs and/or walking aids A study by Fernández-Munoz et al reported that in women with CTS, the following predict the severity of hand pain[10] : Function Thumb-middle finger pinch tip grip force Thumb-little finger pinch tip grip force Depression Pressure pain threshold (radial nerve) Pressure pain threshold (carpal tunnel) Heat pain threshold (carpal tunnel) The study, which involved 224 women with CTS, indicated that these factors are responsible for 36.5% of variance in pain intensity. Diagnostic Considerations These include the following: Focal CNS pathology (multiple sclerosis, tumor, stroke) Proximal median nerve mononeuropathy (eg, pronator teres syndrome) Polyneuropathies Raynaud syndrome Degenerative arthritis in the hand and wrist Differential Diagnoses Acute Compartment Syndrome Cervical Disc Disease Cervical Myofascial Pain Cervical Spondylosis Diabetic Neuropathy Ischemic Monomelic Neuropathy Leprosy Lyme Disease Mononeuritis Multiplex Multiple Sclerosis Neoplastic Brachial Plexopathy Overuse Injury Physical Medicine and Rehabilitation for Epicondylitis Physical Medicine and Rehabilitation for Lateral Epicondylitis Physical Medicine and Rehabilitation for Myofascial Pain Posttraumatic Syringomyelia Radiation-Induced Brachial Plexopathy Surgery for Reflex Sympathetic Dystrophy (Complex Regional Pain Syndrome Type 1) Thoracic Outlet Syndrome Traumatic Brachial Plexopathy Laboratory Studies No blood tests exist for the diagnosis of carpal tunnel syndrome; however, laboratory testing for associated conditions (eg, diabetes) may be performed when clinically indicated. Imaging Studies No imaging studies are considered routine in the diagnosis of carpal tunnel syndrome (CTS). Magnetic resonance imaging (MRI) of the carpal tunnel is particularly useful preoperatively if a space-occupying lesion in the carpal tunnel is suggested. Signal abnormality can be detected in the median nerve in some cases of CTS, but how these abnormalities correlate to diagnosis and physiologic severity is not clear. MRI does not rule out the multitude of other differential diagnoses and is time consuming and resource intensive.[11] Many clinical neurophysiology laboratories are now using ultrasonography as an adjunct to electrodiagnostic studies. Ultrasound potentially can identify space-occupying lesions in and around the median nerve, confirm abnormalities in the median nerve (eg increased cross sectional area) that can be diagnostic of CTS, and help guide steroid injections into the carpal tunnel.[12, 13, 14] Other Tests Electrophysiologic studies,[15, 16, 17] including electromyography (EMG) and nerve conductions studies (NCS), are the first-line investigations in suggested carpal tunnel syndrome (CTS).[18] Abnormalities on electrophysiologic testing, in association with specific symptoms and signs, are considered the criterion standard for CTS diagnosis. In addition, other neurologic diagnoses can be excluded with these test results. NCS in a patient with CTS are seen in the images below. Sensory nerve conduction studies from the left hand of a patient with a several-year history of numbness and weakness (responses from the median nerve in the right hand were completely absent). Note marked slowing of the conduction velocity (CV) to 29.8 and 25.5 m/s for digits 3 and 1, respectively (normal >50 m/s). The amplitude for both also is reduced markedly (normal >10). These findings are consistent with carpal tunnel syndrome. Motor nerve conduction studies from the left hand of a patient with a several-year history of numbness and weakness (responses from the median nerve in the right hand were completely absent). Note that the conduction velocity (CV) across the carpal tunnel segment slows severely to 18.3 m/s (normal >50 m/s) and that the distal motor latency is prolonged at 6.3 ms (normal < 4.2 ms). Amplitudes are low for the wrist and elbow stimulus sites at 4.7 mV (normal >5 mV), but amplitudes are 31% higher distal to the carpal tunnel (at the palm). This discrepancy may represent conduction block (neurapraxia) at the level of the carpal tunnel or coactivation of the ulnar branch to adductor pollicis. Needle electromyography is required to determine whether axonal loss is present. Electrophysiologic testing also can provide an accurate assessment of how severe the damage to the nerve is, thereby directing management and providing objective criteria for the determination of prognosis. CTS is usually divided into mild, moderate, and severe; however, criteria for this assessment usually vary from lab to lab. In general, patients with mild CTS have sensory abnormalities alone on electrophysiologic testing, and patients with sensory plus motor abnormalities have moderate CTS. However, any evidence of axonal loss (eg, decreased or absent sensory or motor responses distal to the carpal tunnel or neuropathic abnormalities on needle EMG) is classified as severe CTS. Changes in electrophysiologic results over time can be used to assess the success of various treatment modalities. The American Association of Electrodiagnostic Medicine has published standards and guidelines that govern the minimum number of studies that should be performed to diagnose CTS.[16] Other quantitative tests, such as thermography and vibrometry, have been shown to be inferior to electrophysiologic examination and, because they have not been supported by controlled studies, are not recommended. Rehabilitation Program Physical Therapy Given that carpal tunnel syndrome (CTS) is associated with low aerobic fitness and increased BMI, it makes some inherent sense to provide the patient with an aerobic fitness and weight-loss program. Stationary biking, cycling, or any other exercise that puts strain on the wrists probably should be avoided. The use of modalities (in particular therapeutic ultrasound) may provide short-term relief in some patients.[19, 20, 21] A study by Incebiyik et al indicated that in patients with mild to moderate CTS, treatment with short-wave diathermy (SWD) can produce significant short-term benefits, including alleviation of clinical symptoms and pain and improvement of hand function. In the prospective, randomized, controlled, double-blind trial, 31 patients (58 wrists) with mild to moderate CTS were treated with a combination of a hot pack, nerve and tendon gliding exercises, and either SWD or placebo SWD, undergoing this therapy five times per week for three weeks. A variety of evaluation measures, including the Tinel sign test, Phalen sign test, carpel tunnel compression test, and Boston Carpal Tunnel Questionnaire (BCTQ) Symptom Severity and Functional Status scales, were used to assess patient outcomes. Significant improvements were found in the patients who underwent SWD but not in those who receivedthe placebo treatment.[22] Additionally, yoga and carpal bone mobilization techniques have some weak evidence for reducing symptoms in the short term.[21, 23] Occupational Therapy Wrist splints with the wrist joint in neutral or slight extension (to be worn at nighttime for a minimum of 3-4 wk) have some evidence for efficacy. Certainly, they are low cost and have very low risk of adverse effects and therefore can be considered as an initial therapy.[24] No evidence suggests that a specific stretching/strengthening program for the hand and wrist is useful for treating carpal tunnel syndrome.[23] Massage and/or nerve-glide techniques offer no proven benefit.[21, 23] Work-site ergonomic assessment, equipment, and/or ergonomic positioning seem to not provide any benefit.[20, 25] Medical Issues/Complications Most individuals with mild-to-moderate carpal tunnel syndrome (CTS; according to electrophysiologic data) respond to conservative management, usually consisting of splinting the wrist at nighttime for a minimum of 3 weeks. Many off-the-shelf wrist splints seem to work well, although theoretically, a custom-made splint in neutral is probably the best choice.[19, 26, 24] Steroid injection into the carpal tunnel has been shown to be of long-term benefit and can be tried if more conservative treatments have failed[27] . Injections may also be worthwhile prior to surgical management or in cases in which surgery is relatively contraindicated (eg, because of pregnancy).[27, 28] Ultrasound measurements of the median nerve can help predict response to steroid injection.[29] . Nonsteroidal anti-inflammatory drugs (NSAIDs) and/or diuretics may be of benefit in certain populations (eg patients with fluid retention or with wrist flexor tendinitis). Vitamin B-6 or B-12 supplements are of no proven benefit.[21] Lack of aerobic exercise (along with increased BMI) seems to be a risk factor for the development of CTS and should be addressed. Surgical Intervention Patients whose condition does not improve following conservative treatment and patients who initially are in the severe carpal tunnel syndrome (CTS) category (as defined by electrophysiologic testing) should be considered for surgery. Surgical release of the transverse ligament provides high initial success rates (greater than 90%), with low rates of complication; however, it has been suggested that the long-term success rate may be much lower than previously thought (approximately 60% at 5 y). Success rates also are considerably lower for individuals with normal electrophysiologic studies.[30, 31, 32] A study by Rozanski et al indicated that in patients who have undergone isolated carpal tunnel release, the greatest risk factors for symptoms in the ambulatory surgery center or problems within 24 hours after discharge are as follows: male sex, age 45 years or above, and participation of an anesthesiologist in the procedure. However, all such symptoms or problems in the study, which were found in 10% of patients, were minor and transient, according to the investigators. The study involved the records of 400,000 adult patients with CTS, as contained in the National Survey of Ambulatory Surgery database, who underwent isolated carpal tunnel release.[33] Consultations Refer patients with suggested carpal tunnel syndrome to a specialist trained in clinical neurophysiology (usually a neurologist, physiatrist, or physical medicine and rehabilitation specialist) for possible electrophysiologic studies. These test results are important for diagnosis, instigation of appropriate treatment, determination of prognosis, and long-term follow-up. Other Treatment Techniques and devices to stretch or manipulate the carpal tunnel have shown some promise but still are not accepted widely.[23] Medication Summary Short (1-2 wk) courses of regular NSAIDs can be of benefit if there is any suggestion of inflammation in the wrist region (eg, flexor tenosynovitis, rheumatoid arthritis). Likewise, if edema is thought to be prominent, then a short course of a mild diuretic may be of benefit. Further Outpatient Care Individuals treated conservatively for carpal tunnel syndrome should undergo a follow-up in 4-6 weeks so that the success of treatment interventions can be assessed. Patients who do not achieve the desired results from conservative treatment should be referred for a surgical opinion. Continued symptoms following carpal tunnel release should prompt referral for repeat electrophysiologic studies. Deterrence No conclusive evidence exists of any intervention that can prevent carpal tunnel syndrome. Complications Carpal tunnel syndrome may continue to increase median nerve damage, leading to permanent impairment and disability. Some individuals can develop chronic wrist and hand pain (with or without reflex sympathetic dystrophy). Prognosis Carpal tunnel syndrome (CTS) appears to be progressive over time (although with considerable fluctuations from week to week) and can lead to permanent median nerve damage. Whether any conservative management can prevent progression is unclear. Even with surgical release, it appears that the syndrome recurs to some degree in a significant number of cases (possibly in up to one third after 5 years).[31] Initially, approximately 90% of mild to moderate CTS cases respond to conservative management. Over time, however, a number of patients progress to requiring surgery. Patients with CTS secondary to underlying pathology (eg, diabetes, wrist fracture) tend to have a less favorable prognosis than do those with no apparent underlying cause. Patients with normal electrophysiologic studies consistently have much less favorable operative outcomes (and more complications) than do individuals with abnormalities on these tests. Axonal loss on electrophysiologic testing also indicates a less favorable prognosis. Patient Education Association versus cause - The association of 2 phenomena does not imply a causal relationship. Using the hands frequently brings on symptoms of carpal tunnel syndrome (CTS), in the same way that exercise brings on angina in patients with coronary artery disease. This association, however, does not necessarily mean that the median nerve damage is caused by use or that it will get worse. (Exercise, in fact, is good for coronary artery disease.) Avoidance of extremes - If a patient's vocation/avocation involves extreme force/repetition/posture/vibration through the wrist, then it seems prudent to seek ways of avoiding factors that cause or aggravate CTS. Exercise - BMI and poor fitness levels do appear to be related to the development of CTS. Source
