Carpal Tunnel Syndrome: What You Need to Know
To Your Health -- CHRC Newsletter
Summer 2002
Peter B.J. Wu, M.D., MPH
PAMF Physical Medicine and Rehabilitation
Carpal tunnel syndrome has become the focus of much attention due to its potential relationship to occupations that require repetitive and prolonged use of the hands - such as keyboarding and mousing. Despite being called the new industrial epidemic by some, carpal tunnel syndrome is not a new medical condition, nor is it well understood by the lay public. Many people develop pain in their hands, wrists, forearms, and neck from their job and worry that they might have developed carpal tunnel syndrome and quite often they haven't. This article will describe what you need to know about carpal tunnel syndrome.
What is carpal tunnel syndrome?
To understand carpal tunnel syndrome, we first need to learn about the carpal tunnel. The carpal tunnel is a "tunnel" that runs through the wrist, bounded by wrist bones on the bottom and the sides, and the transverse carpal ligament on the top. The tunnel houses the median nerve, which is responsible for sensation and movement in the hand, and nine finger flexor tendons that bend our fingers. Carpal tunnel syndrome is the term used to describe symptoms that result from compression of the median nerve as it passes through the carpal tunnel, causing it not to function properly.
What causes carpal tunnel syndrome?
The common causes include inflammatory conditions such as flexor tenosynovitis (inflammation of flexor tendon sheaths), rheumatoid arthritis; metabolic conditions such as diabetes, hypothyroidism; mechanical conditions such as fractures and tumors; other conditions such as pregnancy and dialysis. In a nutshell, any condition that causes abnormal pressure in the carpal tunnel can affect the median nerve and lead to carpal tunnel syndrome.
What are symptoms of carpal tunnel syndrome?
The median nerve supplies feeling to the thumb, index, middle, and half of ring fingers (3 1/2 fingers) and provides function for a few muscles in the hand. Therefore, the most frequent complaint is pain, tingling, and numbness in the fingertips except for the little finger. However, patients quite often report these symptoms in the entire hand. "Dropping things" is a frequent complaint. Patients may also complain of thumb and index finger weakness. Wasting of muscles in the ball of the thumb is sometimes noted in more advanced cases. Symptoms often worsen at night and patients frequently wake up because of pain, tingling, or numbness and find relief by shaking their hands - characteristic of carpal tunnel syndrome. Occasionally, the pain may radiate up the forearm to the shoulder and sometimes the neck.
Work-related carpal tunnel syndrome
It is estimated that 47% of cases of carpal tunnel syndrome are work-related. The risk factors for developing carpal tunnel syndrome include:
1) Repetitive motion, particularly repetitive flexion and extension of the wrist, has been shown to increase the pressure in the carpal tunnel for individuals whose work requires repetitive use of their hands and wrists.
2) Forceful work such as gripping, grasping, holding, torquing, pulling, and pushing that involves excessive contraction of hand muscles can lead to fatigue and will increase the risk of injury if coupled with high repetition.
3) Awkward posture, if sustained for long periods of time can also increase the risk of developing carpal tunnel syndrome. Poorly designed and positioned office furniture contributes significantly to bad posture. It has been shown that pressure in the carpal tunnel is highest in wrist extension, followed by flexion, and lowest in neutral position. As a result, prolonged wrist extension or flexion subjects the median nerve to increased stress.
4) Vibration such as the use of hand-held power tool also increases carpal tunnel pressure.
5) Mechanical stress from too much force applied to the wrist when using hand tools without using sufficient padding can result in higher carpal tunnel pressure.
An ounce of prevention
It becomes easier for us to implement the prevention program once we understand the risk factors that can precipitate carpal tunnel syndrome before the problem gets a chance to build up. It is advisable not to hold objects such as a pen, steering wheel, or working tools too tight and too long. Good posture is extremely important in preventing carpal tunnel syndrome and other work-related injuries. Computer users should keep their hands and wrists in a relaxed position and avoid pounding the keyboard with excessive force. The key points in good posture include sitting with the back well-supported, relaxed shoulders, arms relaxed at the sides of the body, with feet on the floor or on a footrest. The computer should be placed directly in front, and at eye level so that the neck does not bend or extend or turn too much. The hands and wrists should remain in a relaxed position. Excessive side to side movement, flexion, and extension of the wrist should be avoided. Ergonomic evaluation at work and getting certain equipment such as trackball, split keyboard, computer tray, and wrist rests can be very beneficial. However, expensive equipment does not guarantee benefits, thus common sense and personal need should dictate the modifications of workstation and equipment. Proper protection such as gloves and padding should be used when handling vibrating tools. Taking frequent small breaks -- 1-2 minutes every 30-60 minutes -- to do simple stretching of the neck, shoulders, forearms, and hands is extremely valuable for people doing repetitive and strenuous work.
How is carpal tunnel syndrome diagnosed?
The diagnosis of carpal tunnel syndrome is made on the basis of history and physical examination. Nerve conduction studies (NCS) and electromyography (EMG) can confirm the diagnosis. NCS/EMG is the gold standard for establishing the diagnosis: NCS evaluates how fast nerve impulses are conducted through the median nerve; EMG evaluates electrical discharges by the muscles. EMG can distinguish true carpal tunnel syndrome from other neuromuscular disorders that mimic carpal tunnel syndrome such as cervical radiculopathy (an injury of a nerve root of the cervical spine), peripheral neuropathy (dysfunction of the nerves outside the spinal cord), ulnar neuropathy (an injury of the ulnar nerve in the arm), thoracic outlet syndrome (compression of the nerves that pass into the arms from the neck or blood vessels). It is important to rule out other causes to avoid unnecessary surgery. A negative NCS/EMG test indicates absence of significant nerve involvement and thus favors conservative treatment (see below). Magnetic Resonance Imaging has the advantage of revealing the anatomical details around the median nerve and carpal tunnel, but it is mainly used in acute trauma and for further investigation in cases not improved by surgery.
How is carpal tunnel syndrome treated?
1) Conservative measures
It is important to determine the underlying cause of carpal tunnel syndrome, as certain conditions such as pregnancy or hypothyroidism are temporary or correctable, so that conservative approach would be quite appropriate. The patient should avoid work or leisure activities which aggravate the condition. A neutral wrist splint, i.e., the wrist is not in flexion or extension, to be worn day and night, is usually very useful in decreasing the symptoms. A neutral wrist splint provides better symptom relief than a splint which keeps the wrist in the extended position, as the diameter of the carpal tunnel is largest in neutral position. Anti-inflammatory medications such as ibuprofen, naprosyn, and many others can provide some relief by reducing swelling and inflammation. Referral to a hand physical therapist can be beneficial as the therapist can spend more time evaluating workplace ergonomics, recommending proper equipment, and reviewing principles of work hygiene and proper posture if it is work-related. The hand physical therapist can provide treatments including electrical stimulation, contrast bath (immersion of hand into warm and cold water alternatively), ultrasound, soft tissue mobilization (manual therapy to mobilize soft tissues), and therapeutic exercises as clinically indicated. Certain stretching exercises are helpful in releasing tightness of the finger flexor tendons and some may be effective in stretching out the transverse carpal ligament and increasing the diameter of carpal tunnel. The hand physical therapist can apply cortisone on the skin and use electrical current to move the molecules of cortisone through the skin down into the carpal tunnel by a process called iontophoresis to decrease the inflammation and swelling. Direct cortisone injection into the carpal tunnel can be useful in providing symptom relief for months by reducing the swelling and inflammation within the carpal tunnel and relieving the pressure on the nerve. The injection is also used to evaluate whether the median nerve is the only culprit of the patient's symptoms, i.e., if the patient does not get even temporary relief or gets only partial relief from the injection, this suggests other coexisting problems are causing the patient's symptoms. Good response to injection may also predict the patient will most likely improve with surgery.
2) Surgical intervention
Surgery may need to be considered if conservative treatments, described above, fail to provide adequate symptom relief and improvement. Surgery may also be indicated with significant NCS/EMG findings and hand muscle wasting. Carpal tunnel release, as the surgery is called, is the definitive treatment and is a very successful procedure. Cutting the transverse carpal ligament is the standard surgical procedure to relieve pressure on the median nerve. Surgical treatment typically involves either open or endoscopic release of the transverse carpal ligament. Open release involves a mid-palmar incision at the wrist through which the transverse carpal ligament is cut, and the incision is closed. Endoscopic release involves smaller incision(s) through which an endoscope (an instrument with a camera for viewing the interior) is inserted to visualize the transverse carpal ligament before it is cut.
Which surgery is preferred?
Open release provides good exposure and thus the potential risk of injury to major structures is less than with endoscopic release. However, patients who undergo endoscopic release may demonstrate a quicker functional recovery, less postoperative pain, and less scarring than those who undergo open release. Endoscopic release is limited in view and access and is thus not appropriate for conditions such as tumors, fractures, wrist abnormalities, proliferative synovitis (excessive thickening and inflammation of synovial membrane), arthritis, and previous carpal tunnel release. Incidence of recurrence of carpal tunnel syndrome after endoscopic release is slightly higher than after open release because limited view and access may result in incomplete release of the transverse carpal ligament.
The experience and preference of individual surgeon mostly determine the choice of surgical procedure in uncomplicated carpal tunnel syndrome. However, the preference and concerns of the patient such as postoperative pain, scars, and return to work also will affect the surgeon's decision. The attending surgeon directs postoperative care and hand physical therapy. The treatment protocol may vary somewhat from surgeon to surgeon. 85-95% of patients have good to excellent results in terms of improvements in their sensory and motor functions after surgery.
Conclusion: Carpal tunnel syndrome is a common condition caused by compression of the median nerve and is related to various medical conditions and risk factors. Definitive diagnosis can be made by NCS/EMG. It responds well to appropriate conservative treatments, and if not, surgical interventions are successful most of the time.
Disclaimer: Information contained herein is the opinion of the author(s) and not necessarily that of your health care provider, the Palo Alto Medical Clinic, the Palo Alto Medical Foundation or Sutter Health. This information is provided for your general information and education only, and should not be relied upon for personal diagnosis or treatment.