Carpal tunnel syndrome – Definition, Anatomy, Symptoms, Causes, Stages, Treatment with surgery, Pictures

Carpal tunnel syndrome - Definition, Anatomy, Symptoms, Causes, Stages, Treatment with surgery, Pictures

Carpal tunnel syndrome medical terminology

Carpal tunnel syndrome (CTS) is one of the most well-known and frequent form of median nerve entrapment, and accounts for 90% of all entrapment neuropathies. Hence CTS can strike anyone and result in serious consequences, medical awareness of the problem and its causes is crucial to decreasing the risk and preventing the syndrome’s development. This article will discuss everything you may need to know about CTS from its causes to cure and ways of prevention.

Carpal tunnel anatomy

To obtain a good interpretation of the carpal tunnel syndrome, we have to understand the anatomy of the carpal tunnel first. The carpal tunnel or canal sounds like a narrow pass in gigantic mountains; a pass located in the wrist that connects the forearm to the hand. The canal has its boundaries and contents.

Carpal Tunnel Syndrome - Symptoms, Causes, Treatment, Exams and Exercise
Image Credit: Mayo Foundation,.

Firstly the carpal tunnel is bounded by bones of the wrist ‘carpal bones’ and flexor retinaculum; a fibrous band on the palmar side of the hand which is named transverse carpal ligament. On the other hand, inside the canal pass several tendons from the flexor group of forearm muscles and the median nerve.
The median nerve, which is the structure of interest in this article, after receiving some inputs from the brachial plexus ‘a network of nerves originating from the lower four cervical nerves and first thoracic nerve’ passes through the arm and the forearm until the carpal tunnel in the wrist, to supply motor innervation to the first and second lumbrical muscles of the index and middle finger. It also supplies the muscles of the thenar eminence ‘Thee-nar or thumb muscle’ by a recurrent thenar branch. The median nerve supplies sensation to the skin of the palmar side of the index, the thumb and middle finger, half the ring finger, and the nail bed.

What is meant by carpal tunnel syndrome?

Carpal tunnel syndrome is a medical condition that happens due to entrapment of the median nerve as it travels through the wrist at the carpal tunnel ‘as illustrated in the anatomy above’.

Epidemiology ‘frequency of incidence’

In the US, carpal tunnel syndrome is the most common entrapment neuropathy, affecting one to three cases per 1000 subjects per year. The National Center for Health Statistics states that approximately 260,000 carpal tunnel release surgeries are performed each year; Nearly 47% of all cases of carpal tunnel syndrome are caused by work-related activities, and fortunately, approximately 1% of people with carpal tunnel syndrome may develop permanent injury to the affected hand.

Caucasians have higher risk of CTS compared with other races such as non-white South Africans. Females are probably at highest risk of developing carpal tunnel syndrome; the female-to-male ratio is 3-10:1! The peak age for developing CTS is 45-60 years.

What is the main principle of CTS?

Whatever the causes were, the main issue is high carpal canal pressure. This pressure causes obstruction to venous outflow, edema formation, and finally, ischemia to the nerve. Therefore, symptoms and signs begin to arise.

How do you get CTS?

Most commonly, combination of repeated hand activities and health conditions put pressure on the median nerve by decreasing the space in the carpal canal. Obesity, hypothyroidism, arthritis, diabetes, pre-diabetes ‘impaired glucose tolerance’, and trauma as well are among common health conditions that could increase the risk of developing the disease. Carpal tunnel syndrome has been correlated to body mass index (BMI) increase in several studies. Moreover, if you have Hypothyroidism, a condition in which the thyroid gland does not produce enough hormones, your body, due to a metabolic error, tends to accumulate some chemical substances, as mucopolysaccharide, in the carpal canal. With diabetes, researchers believe that high blood glucose levels cause the tendons in the carpal canal to become glycosylated, thus inflamed and less able to slide freely. Medical research has shown that approximately 20 percent of people with diabetes will get CTS. Finally, a list of autoimmune diseases instigates the body’s immune system to abnormally attack its own tissue, causing widespread inflammation, which, in many cases, affects the carpal tunnel. This list include rheumatoid arthritis, systemic lupus erythematosus, and thyroiditis, which can lead to hypothyroidism.
Many other medical conditions may play a significant role in increasing the susceptibility to CTS. Take for example, Down syndrome, Amyloidosis ‘a progressive disorder of the connective tissues’, acromegaly ‘a disease that leads to abnormally large hands and feet due to excessive growth hormone’, and finally tumors on the median nerve ‘removal of such tumors often resolves the CTS in such cases’.

Relation between CTS and your occupation

Whereas many people are concerned with the correlation between their daily work and developing CTS, many studies have shown that exposure to excess vibration, increased hand force, and repetitive hand work may be the initial culprits leading to CTS. The syndrome is even more likely if you have these work-related issues along with other health conditions mentioned above.

Do oral contraceptive and hormonal replacement therapy have to do with CTS?

In previous studies, history of OCT (oral contraceptive), HRT (hormonal replacement therapy), and beta blockers use was reported more frequently by the CTS cases than the negative cases. An association between any factor influencing hormonal status, either exogenous (including oral contraceptives and hormone replacement therapy) or endogenous (i.e., menstrual problems such as amenorrhea, heavy periods, dysmenorrhea, but also menopause), and increased risk of CTS has been considered controversial.

Other risk factors to be considered

In fact, other factors can play a role in eliciting CTS symptoms; as they affect the median nerve without necessarily increasing the interstitial pressure within the carpal tunnel. These could be smoking, alcoholism, vitamin toxicity or deficiency, and exposure to toxins. Broken wrist bones, dislocated bones, and new bone growth from healing bones could not be neglected as responsible factors for CTS symptoms.

However in the most of the time CTS remains an idiopathic syndrome, arising from unknown cause. Abnormalities of the synovial tissue, a specialized connective tissue that lines the inner surface of capsules of synovial joints and tendon sheath, have been implicated as a closely related factor to the development of idiopathic CTS.

Younger people are still at risk due to the over use of handheld electronic devices. A study of a sample of 48 college students was done. The students were classified as either intensive (more than 5 hours of use per day) or non-intensive users, based on self-reported time spent on phones, tablets, and video games. Subjects who used electronics for more than 5 hours a day were more likely to get positive test results indicating symptoms of CTS. The diagnostic tests were followed by ultrasound imaging of the subjects’ hands, which showed that the median nerve was larger in intensive users!

How does CTS present?

Primary symptoms of CTS include pain in the hand, undesirable tingling, or numbness in the distal distribution of the median nerve (thumb, index, middle finger, and half the ring finger). Patients will complain that things slip from their fingers, and a reduction of the grip strength and function of the affected hand. While clumsiness is reported during the day with certain activities requiring wrist flexion, for instance, driving, and reading the newspaper, symptoms are intermittent and tend to worse at night. Patients often describe a phenomenon termed ‘flick sign’, in which shaking or flicking their hands relieves symptoms. Although both hands can be affected, the dominant hand is affected first and more severely.

Pain and numbness in general should be localized to the palmar side of the first four fingers, the sensory distribution of the median nerve, and existing pain in the fifth finger suggests other diagnosis. However, patients might report symptoms outside the median nerve distribution as well. In one study, In 159 hands of patients with ‘electro-diagnostically’ confirmed CTS, symptoms were most commonly reported in both the median and ulnar digits more frequently than the median digits alone. They also reported location of symptoms in areas other than the digits. 21% of patients had forearm numbness and pain, 13.8% reported elbow pain, 7.5% reported arm pain, 6.3% reported shoulder pain, and 0.6% reported neck pain. Obviously, carpal tunnel pain can radiate to shoulder and neck.
Considering that the median nerve carries most of the autonomic fibers, which control involuntary and unconscious functions, to the hand, many patients may also report sensitivity to changes in temperature, especially cold, and a difference in skin color. Rarely, there are changes in sweating. A subjective feeling of swelling in hands or wrists is frequently experienced by patients, but no apparent swelling can be observed. Some clinicians find this symptom has a diagnostic value attached to it.

Stages of CTS

CTS may be classified on the basis of symptoms into three stages:

  • Stage 1: Patients wake up frequently during the night with sensation swelling and numbness in the hand. They also report an annoying tingling in their hands and fingers ‘brachialgia paraesthetica nocturna’. Hand shaking ‘the flick sign’ relieves the symptoms. During the morning, they experience a sensation of hand stiffness.
  • Stage 2: During the day, symptoms also present, especially when the patient remains in the same posture for a long time, or performs repeated movements with their hands and wrists. The median nerve motor deficit begins to appear, and patients begin to report that objects often fall from their hands because they are unable to feel their fingers anymore.
  • Stage 3: It is the final stage where atrophy ‘wasting’ of the thenar eminence is clear. In this stage, the median has a poor response to surgical decompression. In this phase, sensory symptoms may diminish, whereas aching in the thenar eminence persists.

What signs your doctor wants to detect?

Your doctor will test the feeling in your fingers and the strength of the muscles in your hand. Abnormalities in sensory modalities may be present, and can be picked up using maneuvers such as Semmes-Weinstein monofilament testing or 2-point discrimination. A branch from the median nerve stimulates the thenar muscle. If these nerve impulses have been blocked for some reason, the thumb can become weaker or even shrink in size which is called atrophy.

Signs that suggest the diagnosis of CTS

  • Tinel sign: It is performed by gentle tapping over the median nerve in the carpal tunnel region. A positive response is if this causes tingling in the fingers innervated by the median nerve. This sign has low sensitivity and specificity.
  • Durkan’s test: The test is a new variation of Tinel’s sign. Your doctor will press over carpal tunnel by his thumbs and hold pressure for 30 seconds. Pain or tingling in the median nerve distribution is a positive result.

    Carpal Tunnel Syndrome: Physical Exam and Tests
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  • Phalen sign: Also called inverted prayer sign. Tingling in the median nerve distribution is induced when the patient is asked to hold their wrist in complete and forced flexion ‘pushing the dorsal surfaces of both hands together’ for 30–60 seconds.
  • Palpatory test: Doctors may examine the soft tissue over the median nerve directly by palpation for detection of mechanical restriction. Interestingly, this test has a sensitivity of over 90% and a specificity of 75% or greater.
  • The square wrist sign: The sign is positive when the ratio of the wrist thickness to the wrist width is approximately greater than 0.7. Having a square-shaped wrist is a major predisposing factor for CTS according to Dr. Kuhlman (from a study published in American Journal of Physical Medicine). On the whole, currently there is no one test that is 100% accurate for diagnosing carpal tunnel syndrome. However, further investigation can be conducted to establish the diagnosis.

If it is not CTS, what could it be?

Despite that in many cases the diagnosis of CTS is considered clear cut, in other patients, the diagnosis may not be so obvious, and on evaluating the condition, doctors will put other diagnoses into consideration.

Cervical radiculopathy, or cervical disc disease, for example, could be mistaken for CTS since it can also cause abnormal or painful sensations in the hands and wrist. Nevertheless, symptoms of cervical radiculopathy usually begin in the neck and travel down the affected arm and may worsen by neck movements. Acute compartment syndrome, a condition in which the tissue pressure within a closed muscle compartment is increased, can cause symptoms similar to these of CTS, although it usually occurs subsequent to a traumatic event, most commonly fracture. Other disorders, such as mononeuritis multiplex and multiple sclerosis, can cause damage to the median nerve resulting in similar complaints. Other non-neurological diagnoses that may present with a clinical picture similar to CTS include Raynaud’s phenomenon, de Quervain’s syndrome, rheumatoid arthritis, and gout.

How diagnosis of CTS is confirmed?

Electrophysiologic studies: These include electromyography (EMG) and nerve conductions studies (NCS), which are first-line investigations and considered to be the gold standard in the diagnosis of CTS. Nerve Conduction Studies have been developed as a result of the discovery in 1956 that median nerve conduction times are slowed across the wrists of hands in CTS patients. The principle of diagnosis is comparing the latency and amplitude of a median nerve segment across the carpal tunnel to another nerve segment that does not go through the carpal tunnel, such as the radial or ulnar nerve. This method of comparison is more accurate than using ‘normal’ values for the amplitude and latency of individual nerves that may be influenced by many other factors, giving a false negative or false positive result. Such factors include age, gender, finger diameter, or any concurrent systemic disease. Abnormalities on electrophysiologic testing combined with specific symptoms and signs, are considered the standard criterion for CTS diagnosis.

Although imaging studies are of limited role and not considered routine in the diagnosis of CTS, many clinical neurophysiology laboratories are now using ultrasonography to identify space-occupying lesions in and around the median nerve, confirm abnormalities in the nerve, such as increased cross sectional area, that can be diagnostic of CTS, and help guide steroid injections into the carpal tunnel. Magnetic Resonance Imaging (MRI) is excellent for picking up rare pathological causes of CTS such as ganglion, hemangioma or bony deformity; the presence of which may alter the surgical intervention.

Other quantitative tests, such as thermography,  vibrometry threshold testing, and symptom questionnaire ‘hand diagrams’, are not as sensitive as NCS because they have considerable subjective components.

Is surgery mandatory for treating CTS?

The treatment is divided into two main categories: conservative and surgical. Conservative treatment is generally offered to patients suffering from mild to moderate symptoms of CTS.

Conservative treatment modalities

Providing the patient with an aerobic fitness and weight-loss program combined with avoidance of exercises and postures that put strain on the wrist would slightly relieve the symptoms. Moreover, short-term relief in some patients may be achieved by the use of therapeutic ultrasound. 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 (short-wave diathermy) or placebo SWD, undergoing this therapy five times per week for three weeks. Evaluation measures, including Tinel sign test, Phalen sign test, carpel tunnel compression test, and Boston Carpal Tunnel Questionnaire (BCTQ), were used to assess patient outcomes. Significant improvements were found in the patients who underwent SWD (short-wave diathermy) but not in those who received the placebo treatment.

Splinting, however, is based upon measurements of carpal tunnel pressure which is markedly influenced by wrist position and hand use. Although there are only a few studies of splinting used alone as a treatment for CTS, and the most useful data probably comes from a trial comparing splinting to surgery, wrist splints with the wrist joint in neutral or slight extension position have some evidence for efficacy. For the reason that they are low cost and have very low risk of adverse effects, they can be considered as an initial therapy.

On the other hand, cryotherapy, muscle stimulation, massage, yoga, nerve gliding, and carpal bone mobilization techniques have some weak evidence for reducing symptoms in the short term.

Acupuncture, an ancient technique of traditional Chinese medicine, has long been used to treat chronic pain, and studies have suggested that it relieves symptoms at least slightly better than a placebo. Researchers from Massachusetts General Hospital recruited 80 people with mild to moderate CTS. People in the study were split into three groups, two of which received 16 sessions of electro-acupuncture over eight weeks, either on their affected wrist and forearm or on their ankle opposite that arm. The third group received ‘sham’ electro-acupuncture, which used needles that didn’t penetrate the skin on fake acupuncture points. The three groups reported improvements in pain and numbness. However, the measure of nerve conduction at the wrist only improved in the groups who had real acupuncture!

The role of drugs

Non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or aspirin, may help relieve the pain in the short term. However, there is no evidence that these drugs improve CTS, especially if it is not due to an underlying inflammatory condition.

Steroid injection into the carpal tunnel has been shown to be of long-term benefit. Injections may also be used prior to surgical management or in cases in which surgery is relatively contraindicated, because of pregnancy, for instance. The response to steroid injection can be followed up by ultrasound measurements of the median nerve. A number of studies have demonstrated the neuroprotective effects of progesterone and its influence on the recovery after neural injury. A randomized controlled clinical trial, where 78 patients with carpal tunnel syndrome were assigned to two groups, compared the long-term effects of progesterone and corticosteroid local injections in patients with mild and moderate CTS. Measures including pain and electrophysiologic findings, improved in both groups and there were no meaningful differences between the two groups regarding mentioned variables except for functional outcome, which was significantly better in progesterone compared with corticosteroid group at 6-month follow-up.

Anticonvulsants, such as gabapentin and pregabalin, which have come to be administered for various types of neuropathic pain, were found to be partially effective and safe in symptomatic treatment of CTS patients. Eventually, vitamin B-6 and B-12 supplements are of no proven benefit against the disorder.

How Effective Is Carpal Tunnel Surgery?

Empiric evidence has shown that carpal tunnel surgery is effective. In the United States, carpal tunnel surgery is the most commonly performed surgical procedure on the hand. Generally speaking, patients whose condition does not improve following conservative treatment and patients who initially are in the severe CTS category should be considered for surgery. Although surgical decompression remains the treatment of choice in patients not responding to conservative therapies, one study aimed to assess the effectiveness of standard open decompression by analysis of symptomatic and functional improvement. A self-administered Boston questionnaire was used to assess symptom severity and functional status pre- and post-surgical intervention. 88% of patients had a significant reduction in the symptom severity score, while improvement in function status score was achieved in 79%. However, it has been suggested that the long-term success rate may be much lower than previously thought (approximately 60% at 5 years).

pros and cons of carpal tunnel surgery
Image Credit: Mayo foundation.

Regarding the operation, the main principle is to make the tunnel wider. The simplest way to achieve this is by cutting the transverse carpal ligament, converting the carpal ‘tunnel’ into carpal ‘trench’. Although open and endoscopic surgical techniques are available, potential benefits of endoscopy, including quicker functional recovery, must be weighed against the technique’s increased cost and higher complication rate.

Preventing carpal tunnel syndrome

There are no proven strategies to prevent CTS, though you can minimize stress on your hands and wrists with several methods. Avoiding and control of all previously mentioned risk factors might help prevent the median nerve disorder. Healthy habits, such as avoiding repetitive stress and posture modification through use of ergonomic equipment or wearing a wrist splint while sleeping, might be of crucial importance as well. In addition, stretches and isometric exercises before the activity and during breaks will aid in alleviating tension at the wrist, and will aid in prevention for persons at risk.

Taking good care of general health, staying at a healthy weight, and getting regular exercise would help as well.

Examples of stretching exercises:

  • Prayer stretch: Put your palms together in front of your chest just below your chin, slowly lower them toward your waistline, keeping your hands close to your stomach and your palms together, until you feel a mild to moderate stretch under your forearms, and hold like this for at least 15 to 30 seconds each time.

    Can physical therapy help carpal tunnel syndrome?
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  • Wrist flexor stretch: Extend your arm in front of you with your palm facing downwards, bend your wrist, pointing one hand toward the floor with your other hand, gently bend your wrist farther until you feel moderate stretch in your forearm, and hold like this for at least 15 to 30 seconds each hand.

    carpal tunnel syndrome exercises that really work
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  • Wrist extensor stretch: Extend your arm in front of you with your palm facing downwards, bend your wrist, pointing your hand upwards with your other hand, gently bend your wrist farther until you feel a moderate stretch in your forearm, and hold like this for at least 15 to 30 seconds each hand.

    How do you stretch your wrists?
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To conclude, CTS is merely a very common condition with several risk factors, causes and serious complications, yet this can be avoided through various simple measures. Awareness of this medical illness can not only help in preventing the problem, but also early detection and better outcomes.

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Dr. Omar Elashrii
About Dr. Omar Elashrii 4 Articles
I am working as an orthopedic surgeon and part-time medical writer. I graduated from Alexandria university medical school in 2014. After I have finished my internship year, I worked as a family medicine health care unit first doctor for one year. Currently, orthopedic surgery is my field of interest and profession.

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