WHAT EXACTLY IS CARPAL TUNNEL SYNDROME?

• Carpal tunnel syndrome is the compression of the median nerve specifically at the area of the wrist.
  
• The floor of the carpal tunnel is made of eight small wrist bones stacked in two rows of four (the carpus) forming a semi-circle. The roof of the tunnel is a thick ligament that attaches from one end of the semi-circle to the other (the transverse carpal ligament).
  
• Nine tendons pass through this tunnel that measures about the width of the index finger. The tendons are the rope-like portion of the muscle that attaches the muscle to the bone. The majority of the muscles that move the wrist and the fingers are the forearm muscles that originate at the inside edge of the elbow and end at the wrist or in the fingers..
  
  
  
  • Four of the nine tendons passing through the carpal tunnel bend the tips of the fingers.
    
  • Another four of the nine tendons bend the middle joints of the finger.
    
  • The ninth tendon bends the thumb tip.
  
  
• The median nerve also passes through this tunnel. The nerves are the long power cords that run from the spine all the way to the fingers and toes. The median nerve is responsible for providing power to the muscles at the base of the thumb (the thenar muscles) and for sensation in the thumb, index, middle, and part of the ring fingers.
  
• If there is any swelling of the tendons or in the tendon sheath, or if there is thickening of the ligament, the nerve (which is the softest structure in the tunnel) gets "pinched" or compressed. With enough compression, carpal tunnel symptoms occur. If the compression is severe or occurs over a long-period of time, the nerve may actually change shape and flatten causing some permanent damage.

SYMPTOMS

• Numbness and tingling in the thumb, index finger, middle finger and ring finger.
  
• Waking up during the night with the hands numb. Numbness may improve by shaking the hands or hanging them down.
  
• Pain and aching at the base of the thumb and in the wrist.
  
• "Cramping" in the thumb.
  
• Feeling as if there is a band of pressure around the wrist.
  
• Occasionally feeling "electrical shocks" over the front part of the wrist.
  
• Weakness
  
• Feeling clumsy and frequently dropping objects.
  
• Poor circulation or feeling that the fingers are cold.
  
• Difficulty picking up small objects such as coins, pills, or a needle.
  
• In advanced cases, the muscles at the base of the thumb become weaker and "waste away" (atrophy). Muscle atrophy is an advanced sign of severe nerve compression. If you notice any muscle wasting, seek medical attention immediately as the pressure on the nerve needs to be relieved as quickly as possible, usually through surgery.
  

OCCUPATIONAL CAUSES

Currently, there is some debate as to the cause of carpal tunnel syndrome being occupational or genetic - especially in regards to developing from keyboard use. Even if there does tend to be a genetic predisposition towards the development of the syndrome, occupational causes will play a role in the progression of the symptoms. These activities have been shown to increase the pressure on the median nerve as it travels through the carpal tunnel.

• Activities that require repetitive wrist and/or finger bending and straightening.
  
• Forceful grasping or pinching of tools or objects, especially if the wrist is bent at an angle.
  
• Awkward positioning of the hand and wrist during activities.
  
• Direct pressure on the wrist (for example, leaning the heel of the hand on the wrist rest or desk).
  
• Use of vibrating, hand-held tools.

ERGONOMICS

Some tips for relieving the pressure on the median nerve and preventing carpal tunnel syndrome.

• Maintain a neutral wrist position during activities. Avoid bending, extending or twisting the wrist during activities.
  
• Avoid positioning the wrist in a bent position (towards the palm of the hand) for any length of time (for example, when sleeping).
  
• Use the stronger shoulder muscles to perform or inititate activity and don't isolate finger or wrist movement by planting the wrist down.
  
• Avoid using a sustained pinch or grip, especially if the wrist is not in a neutral position.
  
• Minimize repetition. Periodically rest the hands briefly during repetitive or stressful activities (microbreaks of 10-15 seconds). Stretch often during repetitive activity.
  
• Alternate hands during activities if possible so that they share the workload.
  
• Alternate work activities so the hands are not performing any one task repetitively for any length of time.
  
• Slow down the activity.
  
• Use the lightest grip possible (on tools, pens, the mouse, the steering wheel, etc.) that still allows you to maintain good control.
  
• Use the least amount of force necessary during the activity (for example, don't pound on the keyboard).
  
• Use the appropriate tool for the job.
  
• Use ergonomically designed tools if available (modified or padded handles, larger grips with good traction, handles with modified designs) that help you maintain the neutral wrist position.
  
• Keep tools in good condition and cutting edges sharp (reduces the force needed to use the tool).
  
• Use gloves that dampen vibration if you are exposed to high frequency vibration.

A visual of the carpal tunnel.

Marji Hajic is an occupational therapist and a certified hand therapist practicing in Santa Barbara, California. For more information on hand and upper extremity injuries, prevention and recovery, please visit Hand Health Resources.