What's in the Tunnel?

Saturday, May 6, 2006 | 0

By Jomar Almeda

One of the more commonly encountered disease entities involving the hand and wrist in the industrial setting is CARPAL TUNNEL SYNDROME (CTS). The tunnel's name was derived from the Greek word "karpos" which means wrist. The syndrome more specifically refers to an entrapment neuropathy of the median nerve at the wrist. Although some individuals are able to tolerate the symptoms in its early stage, the continued presence of factors or combination of factors causing it could lead to further nerve damage and more severe symptoms. For years, nothing much have been written as to the approach in the diagnosis and management of CTS until endoscopic procedures were introduced in the past decade.

Anatomy:

The tunnel is situated at the volar or ventral aspect of the wrist, right at the base of the palm. The walls are formed by the carpal bones, being bounded medially by the hamate and pisiform, and by the scaphoid and trapezium laterally. Running from the medial to the lateral wall, the transverse carpal ligament forms the roof of the tunnel. Beneath the tunnel lies the 9 flexor tendons of the digits, and the median nerve. The motor branch of the median nerve sends signals to specific muscles of the hand, while the sensory branch relays sensory information from the palm, the thumb, forefinger, middle finger, and the lateral half of the ring finger. There is only so much room in the tunnel to accommodate the flexor tendons and the median nerve, such that swelling from any of these structures produces compression symptoms, as the transverse carpal ligament does not stretch.

Causes:

Carpal tunnel syndrome can come about even without an identifiable cause. Often however, it has been associated with some mechanical problems in the wrist as a result of an injury, forceful and repetitive hand and wrist motion, and prolonged exposure to vibrating hand equipments. Arthritis, diabetes, hypothyroidism, and pregnancy are among the other predisposing factors. Although both sexes may be affected, females are 3 times more likely to develop CTS than males. Individuals with congenitally narrow carpal tunnels will also be more at risk than those with spacious tunnels. Obesity has been implicated with increased risk of CTS as well.

Symptoms:

Symptoms of CTS as described in textbooks include pain, numbness and/or tingling along the palm and digits, innervated by the median nerve. In some instances, such sensations may radiate up to the forearm. They may initially be on and off, but over time, as the condition progresses, becomes constant. A typical patient's sleep is often interrupted by his symptoms, with relief obtained by shaking the hands. There is also a tendency to drop held objects along with a feeling of clumsiness and weakness. In long-standing and neglected carpal tunnel syndrome, there is progressive weakness of the hands and atrophy or wasting of the thenar muscle at the base of the thumb. Left untreated, CTS can be severely incapacitating.

Signs:

To a trained physician, a thorough clinical history, an accurate physical examination, and a positive result with one or more provocative tests will clinch the diagnosis. Tinel's sign, a provocative test to detect nerve irritation, is elicited by light percussion of the median nerve at the wrist. The test is positive when the maneuver produces tingling or "pins and needles" sensation along the distribution of the nerve (thumb, index, and middle fingers). Phalen's test is done by holding both hands tightly in a palmar flexed (reversed prayer) position to at least 90 degrees angle between the forearm and the hand for 30 seconds. A positive test is indicated by numbness or tingling that runs along the said digits. Other provocative tests that some physicians employ include hand elevation and median nerve compression test.

In instances when there is uncertainty with the diagnosis, additional tests may be needed. Electromyographic and nerve conduction studies are usually very helpful. Findings of reduced intensity or delay in transmission of electrical impulse as the wrist is traversed will confirm the diagnosis. X-rays are seldom necessary unless bony changes as a result of previous fracture or a degenerative condition is being ruled out. Blood tests when certain conditions are being considered may also be requested.

Treatment:

The goal of treatment is pain relief and restoration or preservation of function. Night splints for the wrist are worn to maintain proper joint alignment and avoid extremes in position causing increased pressure on the nerve while sleeping. Prescription for splints worn during the day should be individualized, as it can also diminish muscle activity in the hand, produce more swelling, and further aggravation of CTS symptoms. Activity or work modifications are the mainstay of treatment. At work, faulty positioning of the upper extremities should be corrected, along with the appropriate adjustments in work station design (ergonomics). In other words, the station or equipment must suit the user, and not the other way around. Tool handles can be padded for ease of gripping, and heavy items can be moved or transported using a cart. When special devices to minimize stress on the joints are available, they must be used. Pacing, by alternating arduous or repetitive tasks with easier tasks or regular rest periods, reduces the stress on painful joints and allows injured tissues to recover.

Other treatments for CTS include physiotherapy consisting of various passive and active modalities. Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed for relief of pain symptoms. Steroid injections offer dramatic improvement, but results are temporary. It is also not without the risk of puncturing the nerve in untrained hands. When symptoms persist despite a long period of conservative treatment, surgery may be indicated. Carpal tunnel release can be done in either of two ways - by the conventional open method or by the minimally invasive endoscopic technique. The ligament (roof) overlying the median nerve is cut to relieve pressure on the nerve. Some surgeons would excise or trim the transverse carpal ligament edges a little bit more to prevent it from coaptating when the skin is closed, minimizing the risk of recurrence due to scar formation as the wound heals. The choice of what technique to use is determined by the physician's personal preference, training, and expertise. In general, success rate with surgical release is high. Recuperation can take months, but in some cases, depending on the severity of nerve insult, some patients are left with permanent residuals.

Be Gentle with your Joints:

"An ounce of prevention is worth a pound of cure". Other than having to spend hard-earned money for treatment, of great concern is the lost time, suffering, permanent tissue injury, and disability brought about by an illness.

1. Be sensitive to warning signs. Pain is our body's way of telling us to slow down. They are not to be ignored.
2. When our regular work consists of strenuous or repetitive tasks, we should slow down at intervals by doing something light, or by having rest periods.
3. Joints should be positioned correctly while working. Avoid prolonged awkward joint positioning that could excessively stress the muscles and tendons. Avoid keeping the same position for long periods of time.
4. If a particular task had been identified to have caused the carpal tunnel syndrome, the activity must be stopped, or the technique changed.
5. If possible, use the bigger joints and muscles rather than straining the small muscles and joints of the wrists and hands. Instead of continuously carrying something with the hands, a backpack or shoulder bag may be used.
6. Use Personal Protective Equipments, and tools that will make work easier.
7. Learn how to relax. At work, pause at regular intervals to stretch, and do simple range of motion exercises. Deep breathing exercises have been found by many to be beneficial.
8. Lastly, it is vital to always keep in mind Dr. Thomas Fuller's words, "Health is not valued till sickness comes".

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