Carpal Tunnel Syndrome
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.
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, and demographic. A complex interaction probably exists between some or all these factors, eventually leading to the development of CTS. Definite causative factors, however, are far from clear.
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.
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.
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.
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.
- 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.
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).
- 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.
- First and second lumbricals
- Opponens pollicis
- Abductor pollicis brevis
- 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
- 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.
- 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.
Electrophysiologic studies,including electromyography (EMG) and nerve conductions studies (NCS), are the first-line investigations in suggested carpal tunnel syndrome (CTS).
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.
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.
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. Injections may also be worthwhile prior to surgical management or in cases in which surgery is relatively contraindicated (eg, because of pregnancy). Ultrasound measurements of the median nerve can help predict response to steroid injection.
The anticonvulsants gabapentin and pregabalin, which have come to be administered for various types of neuropathic pain, can be used, off-label, for CTS.
Nonsteroidal anti-inflammatory drugs (NSAIDs) and/or diuretics may be of benefit against CTS in certain populations (eg patients with fluid retention or with wrist flexor tendinitis).
The efficacy of gabapentin, diuretics, and NSAIDs is controversial, however, with guidelines from the American Academy of Orthopaedic Surgeons stating that oral agents are no better than placebo in the treatment of CTS.Additionally, vitamin B-6 and B-12 supplements are of no proven benefit against the disorder.
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.
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.