Carpal Tunnel Syndrome
ART Literature Review:
by Everett Johnson, DC, ART
Carpal Tunnel Syndrome.
The carpal tunnel is a well-known site for entrapment of the median nerve and numerous studies exist on the subject. Carpal tunnel syndrome is defined as a peripheral entrapment of the median nerve in the carpal tunnel of the wrist. The carpal tunnel is the pathway from the anterior aspect of the forearm for the tendons of flexor digitorum superficialis and profundus and the tendon of the flexor pollicis longus, along with the median nerve. The tunnel is made up of the carpal or wrist bones which make up the floor (back) and sides of the tunnel, and the transverse carpal ligament makes up the roof or palmar side of the tunnel. A decrease in the dimension of the tunnel causes an increase in pressure and produces ischemia of the median nerve. This compression causes a decrease in conduction of the median nerve, which produces paresthesia (tingling, burning, or numbness) and pain.
The more likely area of the tunnel for entrapment of the nerve is the distal aspect. The tunnel is more narrowed at its distal aspect, where the median nerve is the most anteriorly placed on the radial aspect. The transverse carpal ligament at the distal aspect of the tunnel is thicker and more taut in nature. As median nerve leaves the carpal tunnel it gives a recurrent branch to innervate the thenar musculature. This recurrent branch may pierce the transverse carpal ligament, or emerge just distal to it. In either case, the recurrent branch may become compressed at the distal aspect of the transverse carpal ligament and produce symptoms that affect the muscles of the thenar eminence (base of the thumb).
The condition of carpal tunnel syndrome was described as early as 1854 by James Paget and 1880 by James Putman. In 1893 the condition was called “acroparasthesi”, referring to the nocturnal burning in the hands people suffering from the condition felt. “Tailors neuritis” was used to describe the condition in the early 1900’s as it was a common occurrence in that profession. It was noted as early as 1920 that hyperfunction of the muscles of the hand seen in the group of tailors was the cause of their symptoms. The term carpal tunnel syndrome (CTS) became popularized in the 1950’s. During this time there was an increase in the condition in the population of women recruited to perform manual labor during World War II.
Professions before the industrial revolution were traditionally more trade oriented. This meant a worker performed all parts of a process and changed position and task regularly to complete a given job. With the industrial revolution and the introduction of the production line, people abandoned the idea of being tradesmen for doing single pieces of a job for the mass production of goods. A problem that persisted with this revolution is the treatment of the symptoms of the workers instead of the recent reengineering of workstations and ergonomic changes.
Typically the first symptomatic complaint of people experiencing CTS is numbness or tingling in the fingers, usually at night. Often they report they are woken up or awake experiencing their fingers feeling “asleep”. The symptoms are usually limited to the area of the hand that receives innervation from the median nerve which is the area of the thumb, index, middle and thumb-side of the ring finger. During initial onset of symptoms it may seem that the whole hand is affected. With time the symptoms may become more severe with discomfort throughout the day or may interfere with the performance of normal daily activities. Weakness in the muscles of the thumb may become evident and may lead to clumsy hand movements or dropping of heavier objects. With advanced stages of the syndrome there can be wasting of muscles of the thumb.
According to a European study the prevalence of CTS in women was 5.8% and men 0.6%. The exact prevalence of CTS in the population is not known, however prevalence of CTS in the US is estimated to be 3.4%. Prevalence in different forms of industry is variable as well. As indicated before, persons who sew are more likely to acquire the condition due to the repetitive nature of their task. People performing jobs requiring repetitive wrist motions or awkward positions, or the use of vibrating tools have been shown to have increased risks too.
Previous studies have proposed a “double crush syndrome” in which a lesion along the proximal aspect of the nerve may cause a decrease or impairment of the axoplasmic flow of the nerve, predisposing it to an injury at a distal location. The theory for decreased axoplasmic flow and the effect on the distal region of the nerve has been reported in the literature from the 1940’s. It has been reported that with an increase in compression of the nerve root, it takes less compressive forces at the median nerve to produce symptoms at the carpal tunnel. It is also suggested that the outcome for surgical release of the carpal tunnel was decreased when a more proximal compression neuropathy was present. A prospective study investigated the frequency of CTs and related cervical radiculopathy (2006) and found that the double crush hypothesis was not supported by the data they gathered from the 277 patients examined in their study.
CTS has been associated with diabetes, pregnancy and other hormonal conditions. In a 2006 investigation, researchers reported an increased association with symptoms of CTS and prediabetic state. A 2011 study suggests that 11-25 percent of patients with prediabetes have peripheral neuropathy and up to 21 percent of those may have pain as an associated symptom. They also suggest that persons with prediabetes have less severe neuropathy than those with diabetes.
Proper history, physical examination and electrophysiological studies are all helpful in the successful diagnosis of CTS. The following are some of the classic exams performed.
Phalen’s test is most often used as a screening test for CTS. It requires the patient to flex the wrists, place the back sides of the hands together and force flex the wrists for 30-60 seconds. An increase in the patient’s symptoms of burning, tingling, etc is a positive finding for the exam. Phalen’s is not a perfectly sensitive or specific exam for CTS, but is useful and may indicate further studies need to be conducted. Tinel’s test involves taping the wrists with a reflex hammer. A positive test is indicated by reproduction of symptoms in the fingers or shock-like sensations into the fingers. A 2008 study found these tests to be more specific for the diagnosis of tenosynovitis of the wrist tendons than diagnosing CTS.
Electrophysiological studies include nerve conduction studies and electromyography. Nerve conduction studies are performed with surface electrodes placed on the upper extremity and small electric shocks are applied to the nerves in the forearm, wrist and fingers. Time is measured for the signal to travel the pathway of the nerves. Electromyography is where a fine needle is placed in a muscle and the electrical activity of the muscle is measured. Electrodiagnostic tests remain the preferred method for diagnosing CTS.
MRI and ultrasound have been studied for their use as a diagnostic tool for CTS. MRI has limited diagnostic accuracy and is costly to perform. The accuracy of ultrasound for diagnosing CTS is questionable and there are currently no standard criteria for the diagnosis of CTS using ultrasound.
Other compression neuropathies exist that may mimic CTS. These conditions can be ruled out by doing a thorough physical examination. A patient with C6 radiculopathy will have similar symptoms as someone with CTS, but will likely have issues that are not commonly found with CTS such as pain in the neck and shoulder, especially during coughing or sneezing. These patients may also present with upper back pain localized to the area of the medial border of the scapula. Pain from C6 radiculopathy is typically worse during the day with use of the extremity, where CTS is typically worse at night. These patients also may exhibit weakness on flexing the elbow and extending the wrist with some diminishment of the biceps reflex.
Pronator (teres) syndrome is a compression neuropathy of the median nerve that occurs at the pronator teres muscle in the anterior compartment of the forearm. This syndrome includes the fibrous band called the sublimis bridge of the flexor digitorum superficialis (FDS) where the median nerve passes from the pronator teres and enters deep to the FDS. The sensory symptoms associated with pronator syndrome are similar to those in CTS. However, the condition is not exacerbated with motions involving flexion of the wrist but by forceful pronation of the forearm or direct compression at the pronator teres muscle.
Surgical and non-surgical treatment options are available for the treatment of CTS. Carpal tunnel release is one of the most common surgical procedures performed in the US. This option is typically recommended if conservative management of the condition is not favorable after a 6 month period. The goal of the surgical procedures is to sever the fibrous transverse carpal ligament to allow pressure reduction to occur in the carpal tunnel which ultimately relieves pressure on the median nerve. There are 2 methods for severing the ligament. A traditional open release involves an incision made from the palm to the wrist and the transverse carpal ligament is released. An endoscopic release uses a camera and probe to cut the transvers carpal ligament from the inside and is termed “non-invasive”. Some patients see relief of symptoms almost immediately after the procedure, where others may take months to recover or have a recurrence of symptoms.
Prescription and non-prescription medication are considered for some cases of CTS as an initial form of treatment. NSAIDs, diuretics or corticosteroids may be administered to alleviate the symptoms and help with inflammation. Corticosteroid use should be limited as persons with diabetes or those in a “pre-diabetic” state (see above) may find it more difficult to regulate insulin levels.
Splinting the wrists in an extension position, especially at night, is a very common non-surgical treatment option. Splinting the wrist in extension helps to open or increase the space in the carpal tunnel to allow proper blood flow to median nerve. In cases where the condition may be aggravated by working positions or load the splint is suggested for use at work to help reduce the tension placed on the median nerve. One study compared a group that wore a nocturnal splint for 4 weeks with a group that received no treatment and found that the group wearing the brace had significant symptom improvement at the end of the trial. Some studies argue that splinting the wrist in an extended position while performing a task is detrimental to the muscles as it creates more muscle tension due to resistance of the splint. Currently, the research indicates that there appears to be no added benefit between wearing the splint all day versus wearing it only at night, and no difference between splints that maintain the wrist in a neutral versus extended position.
Tendon gliding exercises have been shown to be effective for alleviation of symptoms related to CTS. Specific exercises focused on movement of the tendons through the carpal tunnel have been shown to significantly reduce pain and increase patients’ functional status in the literature.
Alternative therapies including acupuncture and chiropractic may be beneficial in the treatment of CTS, but little research is provided to support their effectiveness. Several studies have been performed in regard to the effectiveness of Active Release Techniques (ART) for the treatment of CTS. A case report involving 223 patients showed implementation of ART as treatment for CTS resulted in 215 successful resolutions (defined as return to full work capacity with little to no discomfort and required no follow-up treatments). The average number of treatment sessions required for these cases to resolve was 6. 4 percent of the cases had a recurrence that was typically resolved within 2 treatments. It was determined that in half of the patients with recurring issues the individuals had stopped performing the stretching regimen outlined to them during the treatment program. The author also found that recurrence rate after 2 years was less than 10 percent.
A 2006 pilot study looked at the elctromyographic and outcome measure score changes after applying ART to patients with CTS. The EMG analysis did not show a statistically significant difference in before and after applications. The EMG analysis was performed only before and after the first treatment and was not repeated at the end of the study. The outcome scores however showed the patients had a statistically significant improvement in how they rated their pain and functional status after 6 visits. This study had a limited number of participants and they did not perform any long term follow-up of the subjects.
A case study from 1993 reports the use of physician performed myofascial release and patient performed stretches. The wrist, digits and thumb were stretched by the patient to open the carpal tunnel. The study reports this method reduced the patient’s pain and numbness and improved electromyographic results.
Prevention of CTS should encompass all areas of a person’s lifestyle. As mentioned earlier, people with pre-diabetes or diabetes are more likely to have issues with neuropathic pain, specifically CTS. Prevention of diabetes and the pre-diabetic state through lifestyle modification of diet and exercise habits is a great start. Not only are you reducing the risk of developing CTS, but also reducing the risk of developing other detrimental medical comorbidities that accompany diabetes.
Workplace modifications may help in the prevention or reduction of occurrence of CTS. Modification of workstations, working positions, and tools used for tasks can greatly reduce the insult placed on tissues. Rotating workers through different jobs at a factory is a great way to reduce the repetitive nature of the “assembly line”. Workplace conditioning may also be beneficial to reduce the stress of repetitive jobs. Some companies implement exercise and stretching programs, encourage workers to take frequent breaks or to stretch areas that may become overworked to reduce tension and stress.
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