The Carpel Tunnel (CT) is a narrow, rigid tunnel formed by the bones of the wrist on three sides and a strong, inelastic ligament (transverse carpel ligament) on the palmar side.  Travelling through the tunnel are the nine flexor tendons that bend the fingers and the median nerve, which gives feeling to the thumb, index, middle and ring fingers and supples the small muscles which move the thumb, which are used for pinching.

When swelling develops in the carpal tunnel, pressure is put on the median nerve thus decreasing its blood flow.  The resulting lack of nutrients and oxygen causes disturbances in nerve conduction i.e. numbness +/- pain in the fingers.  If compression persists the nerve begins to thin and degenerate.


What causes Carpal Tunnel Syndrome?

Carpal tunnel syndrome can be brought on by one or several factors contributing to increased pressure or swelling within the Carpal tunnel.

  1. Idiopathic: most cases have no specific cause
  2. Repetitive trauma: repetitive movements expose the nerve to compression forces and stretching.
  3. Systemic disorders:  diabetes, rheumatoid arthritis, hypothyroidism, amyloidosis.
  4. Tenosynovitis:  thickening of the tendon synovium (covering of the tendon) caused by friction/overuse of the tendons.
  5. Oedema:  increased fluid within the carpal tunnel, eg pregnancy, cardiac failure.
  6. Abnormal structures protruding into CT canal:  eg; ganglion, displaced fracture, abnormal muscle belly, and arthritic bony spur.



  1. Numbness and tingling: ("pins and needles") in the hand especially at night, but as the severity increases it may also occur during the day with activities such as driving, reading, holding the phone or computer mouse. This is usually felt in the thumb, index, middle and ring fingers.
  2. Pain in the wrist and sometimes up the forearm.
  3. Weakness of grasp and pinch.
  4. Sensory loss: permanent or semi-permanent numbness in the thumb, inex, middle and ring fingers (severe cases).



  1. Nerve Conduction Studies are usually carried out to confirm the diagnosis. They show slowing or absent conduction through the median nerve.
  2. Blood tests may be ordered to investigate if there is a specific cause for the carpel tunnel syndrome e.g. tests for thyroid function, rheumatoid arthritis, diabetes etc
  3. Ultrasound of the wrist to see if there is swelling of synovial tissue in the carpel tunnel or pressure effects on the nerve