What causes carpal tunnel

What is Carpal Tunnel Syndrome?

Carpal tunnel syndrome (CTS) is a common condition that causes pain, numbness, and tingling in the hand and arm. It occurs when the median nerve, one of the major nerves to your hand, is compressed as it travels through the carpal tunnel, a narrow passageway in your wrist. The median nerve provides sensation to the thumb, index finger, middle finger, and half of the ring finger, and controls some small muscles at the base of the thumb.

What Causes Compression of the Median Nerve?

The carpal tunnel is formed by bones and ligaments in your wrist. Inside this tunnel, along with the median nerve, are tendons that bend your fingers and thumb. When the space within the tunnel is reduced, or when tissues surrounding the tendons swell, the pressure on the median nerve increases. This increased pressure can irritate and compress the nerve, leading to the symptoms of carpal tunnel syndrome.

Factors Contributing to Increased Pressure:

1. Repetitive Hand and Wrist Movements:

Activities that involve prolonged or repeated bending of the wrist, such as typing, using hand tools, or playing certain musical instruments, can put stress on the median nerve. Over time, these repeated movements can lead to inflammation of the tendons (tenosynovitis) within the carpal tunnel, which in turn compresses the nerve.

2. Wrist Anatomy:

Some individuals have naturally smaller carpal tunnels, making them more susceptible to nerve compression. Fractures or dislocations of the wrist can also alter the anatomy of the carpal tunnel, narrowing the space available for the median nerve.

3. Medical Conditions:

Several medical conditions are associated with an increased risk of developing carpal tunnel syndrome. These include:

• Inflammatory conditions: Rheumatoid arthritis and other inflammatory conditions can cause swelling of the tendon sheaths around the median nerve.
• Metabolic disorders: Diabetes can lead to nerve damage (neuropathy) and changes in connective tissue, potentially increasing pressure on the nerve. Thyroid disorders, particularly hypothyroidism, can cause fluid retention and swelling in the tissues.
• Fluid retention: Conditions that cause fluid retention, such as pregnancy, menopause, or kidney failure, can increase pressure within the carpal tunnel. Pregnancy-related carpal tunnel syndrome often resolves after childbirth.

4. Other Factors:

Factors such as obesity, which can contribute to general swelling, and certain lifestyle habits may also play a role. While not a direct cause, prolonged awkward postures of the hand and wrist during work or sleep can exacerbate symptoms.

Symptoms of Carpal Tunnel Syndrome

The symptoms of carpal tunnel syndrome typically develop gradually and may include:

• Numbness or tingling in the fingers and hand, often described as a pins-and-needles sensation. This usually affects the thumb, index, middle, and part of the ring finger, but not the little finger.
• Pain in the wrist or hand, which may radiate up the arm to the elbow.
• Weakness in the hand, making it difficult to grip objects.
• Dropping things more frequently.

Symptoms often worsen at night, as many people sleep with their wrists bent. Shaking the hand can provide temporary relief.

Diagnosis and Treatment

Diagnosis usually involves a physical examination, a review of your medical history, and sometimes nerve conduction studies or electromyography (EMG) to assess nerve function. Treatment aims to reduce pressure on the median nerve and may include:

• Wrist splinting, especially at night, to keep the wrist in a neutral position.
• Avoiding activities that aggravate symptoms.
• Medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroid injections into the carpal tunnel.
• Surgery to cut the ligament forming the roof of the carpal tunnel, relieving pressure on the median nerve.

If left untreated, carpal tunnel syndrome can lead to permanent nerve damage and persistent pain and numbness.