What is Carpal Tunnel Syndrome?
Carpal Tunnel Syndrome (CTS) is a chronic condition of the muscles and nerves in the wrist. Motor systems are compromised as the nerves responsible for muscle movement are impaired. Sensory systems are placed on overload as the nerves that detect sensations are activated and heightened.
This condition is called an entrapment neuropathy as the nerves are trapped and compressed. Carpal tunnel is the most common type of entrapment neuropathy. Most sufferers are female and/or older, between the ages of 40 and 60 years. Some occupations have a high prevalence of CTS and this condition is a significant cause of disability and absenteeism.
Incidence in the general population, without adjusting for occupation, is about 14% for people who report impairment in their wrists, or 1 in 5 people reporting problems. Diagnostic tests only confirmed one fourth of those reporting people with clinically diagnosed CTS. Many people may be suffering with nerve entrapment in the wrist without reporting it, or without diagnostic confirmation. The actual figures for CTS may not be known with certainty.
People develop carpal tunnel slowly, over a period of months and once symptoms are felt the damage may be irreversible. Young people may be able to recover better from nerve damage than older people. The degree or severity of the damage will also be a factor in recovery. Not finding the cause of the problem, or repeated exposure to the culprit cause may invite additional insult to the injury.
Nerve damage occurs when peripheral nerves are progressively damaged. Symptoms include unusual or abnormal sensations in the back, neck, shoulders, arms, wrists, hands and fingers. Numbness, tingling and pain are common symptoms of CTS. Causes can include any number of factors including genetic abnormalities and previous traumas.
However, most experts agree that CTS is a repetitive stress injury or a cumulative trauma disorder. Excessive activity and repeated movements cause vigorous stretching and contractions that damage muscles and nerves. In other words, the wrist is damaged due to misusing it, causing trauma or stress. Disuse may also play an important part as only one third of the population exercises regularly. Muscles, tendons and ligaments become atrophied, paralysed, spastic and flabby, inviting physiological damage.
Electrodiagnostic studies are commonly employed to measure nerve conduction and are useful in diagnosis and management of CTS. However, many people complain of CTS symptoms without diagnostic confirmation. Physicians do not rely solely on diagnostic studies to diagnose CTS. People are advised to investigate their environments and triggers for symptoms, and make changes when possible. Treatment ranges from physical therapy, wrist splints, and surgical release of the compression and entrapment.
Symptoms of Carpal Tunnel Syndrome
The nervous system comprises the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS involves the brain and the spinal cord. The PNS is the collection of nerves outside the CNS. A neuropathy is any disorder that affects the PNS, involving the motor nerves and the sensory nerves. Neuropathies may be further classified as diffuse or spreading out and focal or confined to one spot. Carpal Tunnel Syndrome is a compression and entrapment neuropathy but other types of neuropathies include:
- G.I. and Nutrition-Related
- Infectious Diseases
- Chemotherapy Induced
Pain, tingling and numbness are typical symptoms and results of nerve compression. Sensory damage can be transient or long-lasting or can happen suddenly or gradually over time. Damage in carpal tunnel usually develops over time and may be permanent.
People commonly experience sensations alone or in different combinations, which may change over time or depend on the situation. For instance, one person may have developed carpal tunnel over time at work. While typing she may experience numbness in her fingers. But, while attempting to play the guitar, or other musical instrument she feels an urgent tingling in the wrist. Neurologic pain occurs in waves of frequency and intensity. The types of pain commonly experienced:
- Pain – can feel like stabbing, cutting, piercing, drilling, lightning-like, or sharp. Thermal pain can be a sensitivity when a hot and/or cold stimulus is present; may feel like a stinging or shooting sensation. A mechanical pain is when a manual trigger or palpitation causes discomfort like a myofascial trigger point (MTP). Muscle spasms are a type of mechanical pain.
- Tingling – “pins and needles” sensation, an intermittent pricking or stabbing feeling. This type of pain is called paresthesia. It can happen suddenly with no known cause or due to a stimulus.
- Numbness – sensation of falling asleep, weakness, or a reduced ability to feel sensation. A sharp pin prick may feel dull. Can be expressed as clumsiness or dropping things often. This type of condition may be classified as hypoesthesia, or a decrease in sensitivity.
Pain and sensory deficits are individual experiences and depend on the pain threshold, which is the amount of stimulation which provokes a painful response. Other types of pain are classified:
- Hyperalgesia – a heightened, abnormal or elevated response to a painful stimulus.
- Allodynia – an acquired pain that may result from long-term pain. A person may have a reduced pain threshold or become hypersensitive to touch.
- Hyperpathia – a syndrome resulting from repetitive pain with an increased pain threshold and excessive sensitivity.
- Idiopathic – no cause is known or can be identified.
- Phantom – commonly occurs in people with amputated limbs. The brain still believes that the limb is present. In other cases, the pain may have subsided or have been cured, but pain pathways in the brain may have coded a long-term painful sensation.
- Habituated – pain is present but the person may have slowly, over time become used to it physiologically. Cognitively, the person may block the pain from consciousness.
Where Does Carpal Tunnel Syndrome Hurt
While differences in anatomy are not uncommon, and might not be discovered until on the surgeon’s table, most people have similar mechanical problems in their wrist. Morphology anomalies are usually explained by the physician as part of the normal informed consent procedure. Your surgeon or physician, if you do not elect surgery, should tell you that in some people the normal anatomical design may differ slightly.
Compressive neuropathies start with friction in one or several places and in the case of carpal tunnel, that friction makes its way to the digits or fingers on the hand. The digits are the end point in the cascade of physiological mechanisms. Tracing the pathway to the neck or the beginning of the chain, is important both for diagnosing and treating carpal tunnel syndrome.
In addition, the body is complex system and deficits in the lower and mid-back may impact the neck, and so on down the line. Carpal tunnel should be viewed not as an isolated compression just in the wrist but as a complex chain of events. For instance, using a keyboard for typing is a common culprit for carpal tunnel. However, keyboarding is done at a computer with most users sitting down in a chair. The lower back may become weak or overused and the spinal cord may become compressed at that point.
The neck may also become compromised from the seated position. The head is a heavy object weighing 8 to 12 pounds. The seated position may cause the head to fall forward creating a deficit in normal nerve conduction in the neck. In turn, the nerves leading down the arm and into the wrist become compressed. You may think you have just carpal tunnel when really you may have a low back and neck problem.
However, the main pathway is from the neck to the fingers in carpal tunnel syndrome. The influence of coexisting disorders cannot be excluded even if diagnostic tests do not find measureable deficits. A person may feel pain and have actual problems without clinical findings. Widespread sensory deficits are found in patients in the absence of diagnostic confirmation. The main pathway for carpal tunnel and possible locations for pain are as follows:
Trapezius muscles – Researchers have found in a limited study, that all of the subjects studied with CTS, complained of pain in the upper trapezius muscle, the main muscle at the back of the neck. 70% of those patients showed electrophysiological evidence which confirmed a myofascial trigger point (MTP) in their upper trapezius muscle. Patients with worse MTP in the trapezius had worse symptoms of CTS.
Shoulders – sitting in a chair or other behaviors may cause slouching or dropping the shoulders forward. The muscles at the side of the neck tense and constrict 5 major nerves and 2 main arteries that leave the neck. The trapezius muscles & levator scapulae muscles are common culprits in Thoracic Outlet Syndrome (TOS). TOS may be a precursor for CTS.
Arms – the musculocutaneous nerve and radial nerve serve the upper arm. They begin in the shoulder and collarbone region. Compression of these nerves may cause a neuropathy.
Forearm – the median nerve and the anterior interosseous nerve, a branch of the median nerve, and the ulnar nerve supplies the forearm. The radial nerve also descends from the arm to serve the forearm.
Wrist – the nerves that begin at the shoulder, the radial nerve, the median nerve, and the ulnar nerve must cross at the wrist to reach the hands.
Hand – the median nerve enters the hand by passing through the carpal tunnel. The lumbrical muscles in the hand, critical for execution of fine skillful movements of the hand are served by the nerves.
Causes of Carpal Tunnel Syndrome
Friction between the tendons and the median nerve is thought to cause CTS. The median nerve is connected to the spinal cord and communicates with the brain. When the tendons in the wrist and hand are overused and possibly disused, they create friction with the median nerve as it passes through the carpal tunnel. Tunnel friction and pressure sends impulses back to the brain of pain, numbness and tingling.
Research suggests that the sequence of events starts with a shearing injury occurring to the tendon tissues near the carpal tunnel. As the injury heals, scar tissue forms and impairs sliding motion of the tendon. Lack of a proper sliding motion compresses the median nerve. The nerve faces a deficit in blood supply and pressure builds in the tunnel. The pressure buildup diminishes circulation and CTS symptoms develop.
Pressure placed on the nerve in the carpal tunnel can be quantified. Researchers have found that injury is likely to occur when pressure reaches 30 mmHG. Avoiding CTS may be a matter of keeping pressure below that mark. Measuring how the wrist is bending predicts how much pressure is formed. Bending the hand back should not exceed 32.7 degrees. Bending the wrist toward the palm should not exceed 48.6 degrees. Bending the wrist sideways toward the small finger should not exceed 14.5 degrees. Bending the wrist sideways toward the thumb should not exceed 21.8 degrees.
The European Union has listed CTS as an occupational disease since 2003, taking 6th place in frequency in all occupational diseases. An estimated 56% of workers use a computer, but a wide variety of occupations have risk factors for CTS. Keyboard users, hand-held tool users, vibrating tool users, writers and others who use their arms and hands in repetitive motions are at risk. Overloading the musculoskeletal system reduces efficiency, causes limitation and even the loss of work ability. An injury at work can then hamper a person’s psychological status and limit social activities.
- Kids – repetitive strain symptoms previously only seen in adults has also been increasing in incidence in youth. Long hours at the computer may cause poor body posture and musculoskeletal disorders. Keyboard and mouse use may be contributing to neck and back pain, and even carpal tunnel syndrome.
- Time of day – Aggravating symptoms appear to change with diurnal phases. CTS symptoms were found, in one study, to manifest mostly in the morning hours. The median nerve showed increased activation and grip strength was reduced in clinical and electrophysiological measurements in the morning. However, night awakening with hand numbness is considered a symptom of CTS and a risk factor.
- Commuting – repeated and prolonging gripping of anything, in this case the steering wheel of the your car, may lead to CTS.
Carpal tunnel syndrome is found much more often in women and people of an older age, however, researchers have found additional positive associations with CTS. Risks increase with:
- Female gender – women outnumber men with CTS with ratios ranging from 5 to 1 up to 7 to 1.
- Age – Older people have a higher incidence, with the average age for CTS patients being 50 years of age.
- Diabetes – sufferers of CTS have a much higher risk of having diabetes. Diabetic neuropathy is a common disorder for diabetes patients.
- Body Mass Index (BMI) – both male and female patients with CTS showed a greater BMI index. Obesity may increase frequency and force levels of exertion while completing tasks.
- Wrist dimension ratio – a higher wrist (anterior-posterior/medial-lateral diameter) ratio confers a risk for CTS.
- Menopause – In one study, 25.2% of CTS patients had hormonal changes due to menopause, while only 8.8% of the control group had reached menopause.
- Steroid use – 2% of a control group and 8.8% of CTS patients had used steroids.
- Static posture – a fixed, unmoving posture is a risk factor for CTS.
Screening, testing and diagnostic procedures vary. There is no accepted or definitive sequence for the diagnosis of carpal tunnel syndrome. A proper history and examination should include questions about the patient’s occupation and possible hobbies that may trigger CTS. Researchers are even studying sexual positions as a possible risk factor for developing carpal tunnel syndrome. An office visit and physical examination is also useful for ruling out other diagnoses. Some conditions like fibromyalgia, hypothyroidism, tendonitis, arthritis and other conditions may look like CTS at first.
Deciding which patients to send for further testing may be complicated. Patients with minimal, moderate, and severe carpal tunnel pain symptoms may not be related to electrodiagnostic findings or nerve conduction studies. Motor control deficits are also not associated with electrodiagnostic findings. Screening questionnaires help the physician identify those who may benefit from testing, but testing does not always find evidence of CTS. Results from any test depend on the skill and experience of the person conducting the test. Updated calibrations of testing instruments is also a critical factor in accurate results.
The Michigan Hand questionnaire – a widely used hand-specific survey which measures acute and chronic hand disorders. An abbreviated version is available which eliminates redundancy in questions and reduces physician burden. The brief questionnaire retains the psychometric properties of the original and provides a high degree of reliability.
Disabilities of the Arm, Shoulder and Hand (DASH) – patients who answered positively to 2 out of 7 questions were very likely to show nerve conduction deficits in testing procedures.
Patient Evaluation Measure (PEM) – a hand specific screening instrument developed in the UK in 1995. The test is laid out in an uncluttered visual form.
Levine-Katz questionnaire – a 19 question test completed by the patient. 11 questions ask about symptoms and 8 questions ask about functional capabilities.
- Carpal compression test – the physician applies pressure directly on the carpal tunnel and underlying median nerve.
- Pressure provocative test – a cuff is inflated on the carpal tunnel and pressure applied to the median nerve.
- Hand activity level (HAL) – measures the frequency and speed of work on a scale from 0 to 10. Completely idle scores a 0 and the greatest level of work scores a 10.
- Purdue Pegboard test – measures movements of hands, fingers and arms, and fingertip dexterity to screen and select qualified candidates for certain jobs. It is also used in diagnosis and treatment. The test calls for one-handed sequential insertion of pegs into a hole in a board.
- Tinel’s sign test – tapping on the median nerve that produces pain, numbness or tingling is considered a positive result.
- Phalen’s sign test – feeling tingling, numbness, or pain in the fingers within 60 seconds of resting the elbows on a desk, pointing the arms straight up and letting the hands fall forward, indicates carpal tunnel syndrome.
- Two-point discrimination test – touching a finger at two different points and feeling as if the touch is in one spot only, indicates a more severe form of CTS. A metal instrument called a disc-criminator, with two sliding prongs, measures tactile sensitivity. In one research group, the distance increased for obese women and women undergoing breast cancer treatment.
- Qualitatative Sensory testing (QST) – measures stimuli needed to produce specific sensory perceptions. This type of threshold testing may be considered experimental by some insurance carriers and physicians.
- Intraneural Blood Flow – an enlarged and engorged median nerve is typical of CTS patients. A laser Doppler flow meter can be used to measure blood in conjunction with the Phalen test.
- Vibrometer testing – non-invasive vibration sensing using a device with a tuning fork of 128 Hz. Results have a low level of correlation with nerve conduction studies but a moderate reliability with severity of CTS.
- Sonoelastograpy testing – external vibration in the low audio range (50-300 Hz) is applied to tissue which produces waves below the tissue surface. Ultrasound measures displacement in the tissue. It can identify abnormal tissues from injury or tumors. Anatomic or mechanical deficits can be found.
- Ultrasonographic testing – another means to find anatomical abnormalities. This imaging test yields mixed results and does not always correlate with nerve conduction studies. Uses sound reflections to produce an image.
- Electrodiagnostic testing – identifies neurophysiologic information with testing of sensory and motor fibers of entrapped median nerve. Nerve conduction studies (NCS) or electromyography (EMG) measures the electrical signals going to and coming from the brain and spinal cord. Speed and other measures of electrical conductivity are measured with either needles inserted in the muscles or with electrodes placed on the skin. Weak or strong signals may mean the presence or absence of CTS.
- Ultrasonography vs. Electromyography – while ultrasound has a longer history of use, a nerve conduction study is the laboratory diagnostic test of choice because it provides more information on the median nerve and other compression sites.
Carpal Tunnel Syndrome Treatment
Chronic pain in CTS is a multi-dimensional situation with deficits in anatomy, motor coordination and sensation. A treatment approach must combine elements of management including modification of the environment, pain management and possibly curing the nerve impingement. The underlying cause should be discovered and eliminated if possible. Since many CTS cases are occupation related, eliminating the cause may not be possible. Accommodations may be possible to reduce repetitive stress and increase positive musculoskeletal conditions.
Untreated neuropathy can have serious consequences. Permanent nerve damage, changes in sensation, difficulty moving, clumsiness, and reduced abilities may alter the quality of life. While prompt diagnosis and treatment of neuropathy is preferred, many times symptoms do not alert a person until the damage has been done.
Treatment varies among physicians, hospitals, and differs according to country, as well. However, treatment of CTS anywhere will depend on the stage of the disease. Early stage conservative treatment is preferred using medication, a wrist splint, and job modification. More aggressive treatments such as surgery are an option for advanced cases or for those who would prefer surgery. However, surgery may correct the anatomical problems but if the patient goes back to the situation which caused the injury, the same problems may reoccur.
Rest – avoiding the trigger for CTS may cure a problem long-term. Rest may also be a temporary solution, buying time for an evaluation of alternative options. Sometimes a patient may be able to rest, receive therapy to strengthen the musculoskeletal problems and return to work or the hobby that is causing symptoms.
Ice and heat – applying ice or heat to the wrist or affected area may calm inflammation or loosen the muscles and ligaments that have tightened around the nerves.
Nonsteroidal anti-inflammatory drugs (NSAIDS) such as aspirin or ibuprofen may ease muscular inflammation, but may not be effective for nerve damage and provide little relief from irritation
Corticosteroids – with a doctor’s prescription can be taken by mouth or injected directly into the site. Steroids can provide relief immediately for up to a month. Injections could provide relief for up to three months.
Vitamin B6 – supplementing the diet with this vitamin is a common practice to ease symptoms of carpal tunnel syndrome, however its effectiveness is controversial.
Splinting – wearing a brace may force the wrist to stay straight, thereby avoiding wrist bending which increases pressure in the carpal tunnel. Splinting is a conservative treatment and the preferred approach before considering surgery. However, some feel that the brace may actually worsen symptoms because the muscles become atrophied with disuse.
Manual Therapy – physical therapy seeks to restore balance to the entire musculoskeletal system. Specific exercises target the lower back, neck, arms, and wrists. Therapy increases strength and flexibility to lessen pain sensitivity and prevent future injury. Any type of exercise improves immune system functioning and can lessen inflammation associated with CTS.
Laser therapy – Low-level laser therapy (LLLT) is found to have positive effects on motor function with improvements seen in hand and pinch grip strength. However, no benefit was seen in pain symptoms.
Acupuncture – a scientifically proven method for treating CTS using objective measurement and nerve conduction studies. Results were equal to steroid injections and had minimal side effects.
Weight Loss – studies suggest that weight loss alone may cure CTS. Almost all of the patients in one study, who lost 50 or more pounds, reported complete resolution of symptoms.
Electric Stimulation – Low-intensity, low-frequency electrostimulation has a therapeutic effect, possibly by improving pain control mechanisms.
Surgery – outcomes for patients may be better with surgery than with splinting but surgery is not proven better than steroid injections. Three months and up to a year afterwards, surgery patients had less pain, numbness and tingling than those who did not elect surgery. The American Board of Plastic Surgery does not recommend using a brace after surgery but finds that half of all physicians recommend splinting after surgery. The main types of surgery:
- Open carpal tunnel release (OCTR) – local anesthesia or a local block is used. An incision of 2-3 inches is made vertically on the wrist, palm side up. The surgeon divides and cuts the transverse ligament. The ligament eventually heals with scar tissue.
- Mini-OCTR – local anesthesia is used, a limited vertical skin incision is made (1 cm), the proximal part of the carpal ligament is cut, with an average surgery time of fifteen minutes.
- Endoscopic carpal tunnel release – regional anesthesia can be used for surgeries of a short duration. One or two small incisions are made to insert a camera and surgical tools. The transverse ligament is cut, releasing pressure on the median nerve.
The goal of prevention is to reduce the risk of repetitive stress injuries. An ergonomic assessment of the workplace, computing station, or activities may prevent injury and permanent nerve damage.
- Wrist angle – wrist extension should not exceed 32.7 degrees, wrist flexion should not exceed 48.6 degrees, ulnar deviation should not exceed 14.5 degrees, and radial deviation should not exceed 21.8 degrees.
- Mouse and keyboard – should be as close to your body as possible. A platform over the number keypad brings the mouse closer to you. Laptop users can use an external keyboard and mouse to increase comfort. Keep the wrists as straight as possible.
- Monitors – are usually positioned too high causing neck discomfort from looking up.
- Chair – adjust the height to make eyes level with the monitor.
- Breaks – take one every 20 minutes if possible.
- Driving – a tight grip encourages CTS. Switch hands and keep the wrist straight, positioning the hands at three o’clock and nine o’clock.
Speech recognition software – voice to text speech recognition programs can help reduce the number of keystrokes and mouse movement. Speech recognition works not only with word processing programs, but also using web browsers.
Exercise Balls – some forward thinking workplaces and schools are now using blow up plastic balls as seats or replacements for chairs. The balls encourage recruitment of the whole body to maintain balance and a dynamic involvement of the whole musculoskeletal system.
Webcam – an automatic-feedback system used with a webcam can remind users to adjust their posture. The webcam takes pictures periodically of the current posture, and compares it to the desired posture.
New Keyboard and Mouse Designs – new designs for smaller hands and ambidextrous mousing techniques may reduce the risk of CTS. A device called the Keybowl has a built-in mousing function and a novel technique called chording for typing. Learning the new keyboard may take time but reduces finger and wrist motions. The SpacePilot 3D motion controller takes advantage of both hands. The right hand uses a traditional mouse while the left hand uses a device for panning, zooming and rotating.
Engineers and designers continue to research and innovate to protect workers and prevent injury. Adjustable workstations, ergonomic tools, vibrating chairs, and smart mouses are being developed. Guidelines and interventions aimed at risky behaviors and occupations have the potential to prevent more injuries. Employers have a vested interest in identifying the tasks that may put workers at risk. Ergonomic investments make a good economic investment for employers.
However, no designer or employer can take the all the steps needed by an individual. People must learn for themselves, and implement correct ergonomic procedures. They must ask their employer for modifications if necessary. Similar care must be taken for youth in the family at the computer workstation and in the video gaming systems.
However, ergonomics are not the whole story. The musculoskeletal system needs proper breaks from the workstation. The whole body needs appropriate exercise and flexibility to improve strength in the muscles, tendons and ligaments. Misuse of the wrists, arms, shoulder and back must be avoided. But, disuse of the body’s intelligent design must be avoided as well.
Brachial plexus injury – stretched or torn nerves in the brachial plexus may send abnormal sensations to the shoulders, arms and wrists.
Stroke – a cerebrovascular event where blood supply to the brain is diminished and some brain cells die. The symptoms of stroke may appear CTS-like as paralysis or numbness can affect the arms.
Osteoarthritis – a disorder in the joints with cartilage becoming thin, weak or wearing out entirely. Reduced range of motion, swelling and pain may look like CTS symptoms.
Multiple sclerosis – a progressive neurological disability has symptoms of paralysis and disruptions in sensation like numbness and tingling.
Raynaud’s phenomenon – commonly happens in workers who use vibratory tools. Fingers may spasm and cause numbness and pain.
Lipomatosis of nerve (NLS) – may be noticed at birth but almost always detected before 30 years of age. Most patients have deficits in the median nerve and its branches in hand, wrist and forearm.
Complex regional pain syndrome (CRPS) – previously known as reflex sympathetic dystrophy, features pain and neuropathies in the extremities.