DEFINITION
Carpal tunnel syndrome is a condition which causes pain, numbness and tingling in the affected hand. The wrist has a tunnel formed by carpal bones and a flexor retinaculum. Flexor tendons of the hand and the median nerve pass through this carpal tunnel and if this space becomes too small, the median nerve may become compressed leading to paresthesia of the hand. This compression neuropathy in the carpal tunnel may cause characteristic 'pins and needles' of the affected hand.
It is common in females, white population and in the age range 45 to 60 years. In taking the history it's important to inquire about risk factors for developing the condition some of which are:
- Occupational hazard leading to overuse of hands e.g till operators, mechanics or hair dressers
- Chronic conditions like Diabetes Mellitus, hypothyroidism or musculoskeletal disorders
- Pregnancy
- Obesity
SYMPTOMS
The diagnosis of carpal tunnel syndrome comes mainly from the history so it's important to take a good history. Sometimes from the history alone one can hazard the diagnosis and be correct most of the time. All the symptoms are caused by the disturbance of the median nerve in the carpal tunnel and are as follows:
1. Numbness and tingling
- This is a very common complaint which happens mainly at night, called nocturnal paresthesia, and may be relieved by shaking the hand or wrist.
- Certain activities like driving, reading a magazine or knitting are linked to the condition
- The numbness and tingling is usually intermittent.
- It’s common to have carpal tunnel syndrome on both sides although the dominant hand is usually affected more.
- These abnormal sensations affect the palmar region which corresponds to the sensory distribution of the median nerve which is the thumb, index finger, middle finger, lateral half of the ring finger and distal palm. If the symptoms extend to the fifth finger you should think of other diagnoses. However, some patients may fail to accurately describe the sensation especially if autonomic fibers are involved.
2. Pain
- Aching pain occurs primarily in the wrist and radiates distally to the palm and fingers, or proximally to the forearm.
- There may be other associated musculoskeletal disorders causing pain in the upper limb
3. Loss of grip and clumsiness
- Patients may also start losing grip in the affected hand and start dropping things without them noticing ('the hand goes to sleep').
- There may be difficulties in performing activities like buttoning a shirt or pinning a bra
- For severe cases there may be loss of hand function
4. Autonomic symptoms
- The median nerve carries most of the symphathetic nerve fibers of the hand
- Some patients report change in sensitivity to temperature especially cold in the affected hand
- Hands may feel hot or cold all the time
- There may be a change in skin colour
SIGNS/EXAMINATION
As part of physical examination, there are tests that are carried out to show the presence of carpal tunnel syndrome as described below:
Tinel sign/Hoffman-Tinel sign
This has a sensitivity of about 67% and specificity of about 68% according to studies carried out in 2002. The test results should only be used to support the diagnosis and cannot be used to rule out carpal tunnel syndrome. To perform the test, you tap over the carpal tunnel at the wrist and in some cases over the whole distribution of the median nerve from the index finger to the elbow. The test is positive if numbness or tingling is felt in the thumb, index finger, middle finger and lateral half of the ring finger, which is distribution of the median nerve.
Phalen sign
The Phalen test has a sensitivity of 85% and specificity of 89% according to studies carried out in 2002. This means it is a better test as compared to Tinel sign test in diagnosis of carpal tunnel syndrome. To perform the Phalen test, the patient flexes both wrists maximally and holds the dorsal side of both hands together for one minute. Again, the test is positive if numbness or tingling is felt in the thumb, index finger, middle finger and lateral half of the ring finger, which is distribution of the median nerve.
Two point discrimination test
If severe carpal tunnel syndrome is suspected, this test is performed and is not very effective for mild disease. To perform the test the patient is asked to close his or her eyes and the physician uses an instrument e.g paper click to touch one or two points on the hand. If there is sensory damage, the patient may not be able to tell the difference between one or two touches.
OTHER TESTS
Laboratory
There are no blood tests that are done for carpal tunnel syndrome. However, tests for associated diseases mentioned above may be done.
Radiological tests
No imaging studies are done routinely for diagnosing carpal tunnel syndrome. If a mass is suspected to be causing carpal tunnel syndrome an MRI (Magnetic Resonance Imaging) is done preoperatively.
Electrophysiologic study
This includes electromyography and nerve conduction studies. These studies provide an accurate assessment of the severity of nerve damage by analysing sensory and motor abnormalities. This helps in formulating treatment plan and coming up with a prognosis.
CONCLUSION
The diagnosis of carpal tunnel syndrome rests mainly on taking a good history and the tests only help support the diagnosis and plan on treatment. If the condition is not managed properly, the pain can be incapacitating. Also read about a related condition, tendonitis, which is inflammation of tendons.