Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment syndrome, affecting more than eight million individuals annually. Risk factors for CTS include previous wrist fracture, pregnancy, genetic predisposition, diabetes, and arthritis. A higher prevalence is also noted in occupational groups that require tasks that are repetitive and/or cause hand/arm vibrations (e.g., grinders, butchers, computer workers, construction workers).
Symptoms are often described as pain, numbness, and/or tingling of the thumb, index finger, middle finger, and the radial half of the ring finger. Pain may progress to an electric shock like impulse, with weakness, clumsiness, and muscle atrophy of the thenar eminence. While movements that require gripping of the hand seem to make symptoms worse, shaking and flicking the wrist and hand often provides temporary relief.
CLINICAL EXAMINATION
Given that CTS is often misdiagnosed as cervical radiculopathy, pronator teres syndrome, or anterior interosseous nerve syndrome, physicians often require ultrasonography, electromyography, or nerve conduction velocity studies to diagnose CTS. Ultrasonography is often used to measure an increase in the cross-sectional area of the median nerve, as this change has been found to closely correlate with the severity and symptoms of CTS. Electromyography is used to assess abnormal fibrillation potentials and positive sharp waves in muscles innervated by the median nerve (e.g., the abductor pollicis brevis). Nerve conduction studies help to confirm the diagnosis of CTS by detecting loss of conduction speed along the median nerve across the carpal tunnel in the presence of normal conduction speeds elsewhere.
Three reliable outcome measures include the Boston Carpal Tunnel Questionnaire (BCTQ), Disability of Hand and Shoulder Questionnaire (DASH), and Upper Extremity Functional Index (UEFI). Notably, the BCTQ has been shown to possess a high Cronbach alpha, which is indicative of high homogeneity and strong construct validity.
Special tests are still often used as part of the diagnostic process for CTS. More specifically, the carpal compression test may be one of the best screening tools, as it has demonstrated 52.9% specificity and 80.6% sensitivity. The test is performed by adding direct pressure with both thumbs on the flexor retinaculum over the carpal tunnel for thirty seconds, with a positive test described as a reproduction of symptoms. Other tests include Tinel’s test (47.1% specificity, 65.3% sensitivity) and Phalen’s test (35.3% specificity, 59.7% sensitivity). A positive test for both the Tinel’s test and Phalen’s test is the reproduction of familiar symptoms in a median nerve distribution. A positive median nerve tension test (i.e., a neural tissue provocation test using sensitizing maneuvers) may also be present in moderate-severe CTS, and decreased grip strength is often present due to pain inhibition and disuse.
Individuals with mild to moderate CTS demonstrate greater forward head posture and less cervical range of motion in all directions compared to healthy controls; therefore, the cervical spine cannot be overlooked. Although much less common, compression of the median nerve at the elbow is also a competing diagnosis, as the pronator teres, the Struthers’ ligament, and the flexor digitorum superficialis arch have been shown to be sites of entrapment. Notably, a large proportion (i.e., 94%) of patients with CTS has been found to have concomitant symptoms associated with ulnar nerve compression. In some cases, patients can present with signs and symptoms of carpal tunnel syndrome secondary to ulnar nerve compression at the elbow. This is likely due to a number of anastomoses between the median and ulnar nerve, which occur in 8-26% of patients with CTS and 17% of patients with cubital tunnel syndrome. One such anastomosis, known as a Martin-Gruber anastomosis, has been shown to occur under the pronator teres muscle in 15-31% of patients. Interestingly, pronator teres syndrome accounts for 9.2% of median nerve entrapments, second only to the carpal tunnel, and is often misdiagnosed as carpal tunnel syndrome.
TREATMENT
Surgery for CTS should be considered only if conservative treatment has failed or in the presence of severe median nerve damage, as nearly 10% of patients who undergo a carpal tunnel release develop symptoms worse than before surgery. Local steroid injections should also be limited due to increased risk of tendon rupture and/or median nerve damage. As such, conservative measures such as physical therapy, splinting, ultrasound, oral steroids, nonsteroidal anti-inflammatory drugs, and vitamin B6 supplementation should be attempted first.
Physical therapy for CTS may include education, activity modification, soft-tissue mobilization to the surrounding musculature, transverse ligament stretching, carpal bone mobilizations, cervical spine mobilization/manipulation, tendon gliding, nerve gliding, static cupping, and electro-acupuncture. Manual physical therapy, including desensitization techniques and soft-tissue mobilization at potential sites of median nerve entrapment, has been shown to be more effective than surgery in the short-term, and as effective as surgery at medium and long-term follow-up.
ACUPUNCTURE FOR CARPAL TUNNEL SYNDROME
Multiple systematic reviews recommend the use of acupuncture or electroacupuncture in the management of mild to moderate CTS. Acupuncture has been shown to improve pain, numbness, tingling, and muscular weakness in patients with CTS, and it has been correlated with a reduction in the cross-sectional area of the median nerve and improved distal motor latencies via electrodiagnostic studies. Acupuncture has also been shown to be more effective than ibuprofen, local steroid injections, and night splinting. Acupuncture trials have included perineural needle insertions between the tendons of the palmaris longus and the flexor carpi radialis at the flexion wrist crease (PC7) and more proximal in the anterior aspect of the distal forearm (PC4, PC5, PC6). Several clinical trials have also inserted needles near the center of the palm between the second and third metacarpal bones 3 fingerbreadths distal to the flexion wrist crease (PC8), within the first dorsal interosseous muscle on the dorsoradial aspect of the hand at the midpoint of the second metacarpal (LI4), at the lateral aspect of the volar wrist crease in the depression between the radial artery and the abductor pollicis longus tendon (LU9), and over the radiovolar aspect of the center of the thenar eminence (LU10).
Acupuncture with manual and/or electrical stimulation has been shown to decrease pain by promoting endogenous opioids such as beta-endorphin, enkephalins, and dynorphins. Peri-neural electroacupuncture also improves microcirculation via nitric oxide so as to facilitate enhanced intra- and extra-neural blood flow. Recent evidence further suggests that electroacupuncture may promote the proliferation and migration of Schwann cells facilitating neural repair via brain derived neurotrophic factor (BDNF).
DRY NEEDLING FOR CARPAL TUNNEL SYNDROME
While dry needling and acupuncture both use monofilament needles without injectate for therapeutic purposes, dry needling does not attempt to move energy or “qi,” nor does it rely on diagnoses based on traditional Chinese medicine. Dry needling is used by physicians, physical therapists, chiropractors, and osteopaths to treat muscles, ligaments, tendons, subcutaneous fascia, scar tissue, peripheral nerves, and neurovascular bundles associated with a number of neuromusculoskeletal conditions. Despite robust evidence for treating CTS with acupuncture, only 3 studies presently exist on “dry needling”. In patients with mild-moderate CTS, dry needling of forearm myofascial trigger points improved pain severity and BCTQ scores. Patients who received dry needling for CTS have also reported significant improvements in pinch strength compared to controls. Additionally, dry needling with manual stimulation (i.e., unidirectional twisting/winding) has been shown to alter the tissue properties and mechanics of the transverse carpal ligament on real-time ultrasound imaging. This finding is noteworthy, as stiffness of the transverse carpal ligament is correlated with CTS symptoms while stretching it has been shown to improve pain and function.
OTHER CONSERVATIVE INTERVENTIONS FOR CARPAL TUNNEL SYNDROME
Several studies have also reported that static cupping for 3.5 minutes over the volar wrist crease is useful for CTS, particularly when used as an adjunct to “physical therapy”. Static cupping may reduce compression of the median nerve and improve circulation via nitric oxide.
The assessment and treatment of the cervical spine may also be important in the management of CTS, as it has been associated with a number of upper extremity referred pain conditions. Studies have shown central and peripheral hyper sensitization in patients with CTS, and desensitization maneuvers, such as lateral glides of the cervical spine have been shown to improve symptoms. A number of investigators have also noted improvement in CTS symptoms following high-velocity low-amplitude thrust manipulation targeting the cervical facet joints and the carpal bones.
Although not curative, bracing (splinting) is useful for patients with carpal tunnel syndrome, particularly if used within three months of the onset of symptoms. Neutral wrist positioning causes the least amount of pressure in the carpal tunnel and may provide the greatest symptom relief. Notably, in patients with CTS, full-time wearing of a neutral wrist splint has been shown to be more advantageous than wearing at night-time only.
CONCLUSION
Multiple systematic reviews recommend the use of acupuncture or electro acupuncture in the management of mild to moderate CTS. Acupuncture has been shown to improve pain, numbness, tingling, and muscular weakness in patients with CTS. Activity modification, neutral wrist bracing, nerve and tendon gliding exercises, soft-tissue mobilization, transverse ligament stretching, carpal bone mobilizations, static cupping, and cervical mobilization/manipulation, may also be useful in the management of CTS.
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