Carpal tunnel syndrome is a common condition caused by the entrapment of the median nerve in the carpal tunnel resulting in numbness and significant pain in the hand, fingers and wrist.
The carpal tunnel is a complex anatomical region located at the wrist comprising the carpal bones at the ventral side and the transverse carpal ligament on the dorsal side. The Carpal tunnel encloses the median nerve and the flexor tendons.
The median nerve is formed out of the nerves of the cervical plexus (C6- Th1). it travels along the upper arm, forearm and the wrist to innervate the hand. It controls the sensory function of the lateral side of the palm, thumb, index, the middle and half of the ring finger, but not the little finger and the intrinsic finger muscles. The median nerve innervates the thumb muscle. The flexor tendons allow the fingers and thumb to bend. The carpal tunnel syndrome develops with the compression of the median nerve caused by the swelling of the soft tissue in the carpal tunnel. This type of nerve conditions is generally named entrapment neuropathy, causing pain and numbness in the fingers and hand.
The aetiology of carpal tunnel syndrome is unknown. It is thought to origin from one or a combination of the following causes and not from the nerve itself:
Genetic predisposition due to the narrower anatomy of the carpal tunnel
Excessive use of the hand and wrist in specific activities (maneuvering computer mouse and vibrating tools)
Injury to the wrist (fractures sprains) causing swelling of soft tissue
Age and hormonal changes as it is more common in older individuals and women
Underlying medical conditions such as Rheumatoid arthritis, diabetes and thyroid dysfunction (hypothyroidism)
Cyst formation in the carpal tunnel
There are a various risk factors thought to cause carpal tunnel syndrome:
Adult age and elderly individuals
Females are more often affected possibly due to smaller carpal tunnel anatomy
Dominant hand more susceptible
Professions with intense manual activities: manufacturing, sewing, finishing, cleaning, and packaging.
The symptoms of carpal tunnel syndrome begin gradually and increase over time. They include:
Pain, tingling, burning, and numbness of the thumb, index and inner side of the ring finger. They are more evident while sleeping possibly due to a prolonged bending of the wrist.
Symptoms are felt mostly on the palmar side of the hand but can extent to the upper arm
Weakening of grip strength
With ongoing pathology: medial nerve damage, muscle atrophy of the thenar muscle and weakness of the thumb movements.
Early diagnosis of carpal tunnel syndrome is critical to prevent permanent damage to the median nerve. Clinical examination comprises:
Inspection of both hands, arms, right and left shoulder and neck to exclude other conditions
Examination of the wrist looking for swelling, warmth, colour and tenderness at touch
Monitoring of sensation in each finger and muscle strength
Use of special tests, Tinel's test to determine abnormalities of the median nerve (tingling) when it is stimulated with pressure or tapping; and Phalen's test consisting in bending the fingers towards the wrist, triggering the symptoms above
Electrodiagnostic tests to monitor nerve conduction when stimuli are applied to electrodes placed on the nerve
Electromyography to test median nerve activity directly in the muscle using a needle placed in the muscle and not in the nerve
X-rays to examine bone quality and rule out fractures, arthritis
Other tests to visualise the anatomy of the wrist in particular the soft tissues (ultrasound, MRI)
Blood tests to exclude possible medical conditions
Early conservative treatment is the key for reducing the symptoms of carpal tunnel syndrome. If diabetes and arthritis are present they are given medical priority with medical care. Other measures for conservative treatment are:
Immobilisation of the wrist with a splint for approximately 2 weeks (especially at night) is the first remedy to reduce symptoms of a tunnel carpal syndrome
Application of cool pads and administration of NSAIDs in case of concomitant swelling and inflammation
Local steroid injections when more severe symptoms are present
Physical and occupational therapy to modify activities and including stretching and strengthening exercises
Other therapies such as acupuncture, chiropractic care and yoga
In case of prolonged symptoms despite conservative treatment, surgery is necessary. This aims to release the entrapped median nerve. The success rate of surgery is very high. Two approaches are available:
Traditional surgery: Incision along the wrist and palm. The transverse carpal ligament is cut to reduce the pressure on the medial nerve. The skin over the median nerve is sutured together. During the healing process the ligament will repair itself maintaining a larger tunnel size for the nerve and flexor tendons.
Endoscopic surgery: An alternative, minimally invasive approach reduces the wound size and allows for faster recovery. Two small incisions in the wrist and palm are made to insert an endoscope (camera) to visualise the region and the second for the surgical tools. The surgical procedure remains the same as in the traditional approach as in cutting the transverse carpal ligament.
In post-operative rehabilitation the initial care includes:
Immobilisation with a cast or splint for up to 3 weeks
Treatment with analgesics and NSAIDs
Ice pads to reduce inflammation and swelling
Use of the hand can commence immediately after surgery while wearing a brace or without brace. Often minor symptoms remain for a few months after surgery. Strength or grasping activity can resume after 4 weeks post-surgery and full recovery can take up to 1 year. A number of exercises guided by a physiotherapist will assist in gaining strength of the operated wrist.
Although the causality of manual work and the carpal tunnel syndrome remains unclear, a number of measures including occupational health and safety rules at workplace should be implemented to reduce the risk to develop a carpal tunnel syndrome. These recommendations include:
Ergonometric education for correct posture during manual activities (avoid to keep the wrist bent)
Wear gloves or splints
Use workstations designed for optimal posture of hand and wrist
Regular stretching exercises while working
Frequent rests when involved in heavy industrial manual work
Job rotation among employees