Carpal tunnel syndrome occurs when there is pressure and squeezing (entrapment) of an important nerve in the hand called the median nerve. This pressure causes median nerve injury and results in pain, numbness, and weakness in the hand and wrist.
The median nerve and finger flexor tendons pass through a narrow space in the wrist called the carpal tunnel, formed by the carpal bones and enclosed by a fibrous band (transverse carpal ligament or flexor retinaculum). Because the carpal tunnel is very narrow, any irritation of the tendons or any swelling in this space may entrap and compress the median nerve.
Carpal tunnel syndrome tends to occur in adults age 30 to 60 years old and is three times more likely in women than men. This is a very common condition associated with a variety of work-related or medical factors.
With proper treatment, most people completely recover and only a few have permanent nerve damage and loss of hand function.
The cause of carpal tunnel syndrome is not completely understood, but the disorder is associated with factors that compress the median nerve and affect the sensory and motor functions of the hand.
Workers with jobs requiring repetitive use of their hands are more susceptible to carpal tunnel syndrome. Examples include meatpackers, assembly line workers, grocery checkers, garment workers, dental hygienists, and musicians. So far, studies have not proven that excessive use of a computer keyboard or mouse causes carpal tunnel syndrome. In fact, assembly workers are at much higher risk than typists.
Early symptoms include pain and paresthesias (tingling, numbness, and burning sensations) of the thumb, index finger, and middle finger especially at night and after certain activities like driving or holding a book. If the problem worsens, patients experience hand weakness, dropping things, difficulty gripping objects, and clumsiness. Symptoms usually start in the dominant hand, but may be experienced in both hands.
It is important to diagnose and treat carpal tunnel syndrome as early as possible to prevent permanent median nerve damage, loss of hand function, and disability. Usually the diagnosis is based on symptoms and physical exam findings indicative of median nerve entrapment, but sometimes nerve testing is necessary.
Carpel tunnel release surgery is recommended for patients with 6 months of persistent symptoms. This operation involves cutting the transverse carpal ligament at the wrist to provide more space in the carpal tunnel and relieve the pressure on the median nerve.
Open carpal tunnel release is the more traditional approach, which involves making a 2-inch incision in the wrist and cutting the transverse carpal ligament. Endoscopic carpal tunnel release uses two tiny incisions, a small camera, and instruments to cut the transverse carpal ligament. This less invasive procedure shortens the patient’s recovery time.
Both types of surgeries are performed under local anesthesia: medication is injected to numb the tissues and prevent the patient from feeling the surgery, so the patient does not need to be deeply asleep. After surgery, patients need physical therapy to regain hand strength and function, and most patients make a full recovery.
Employers can redesign equipment and adapt activities to fit the human body based on a field of study known as ergonomics. Work areas may be redesigned to allow people to maintain a neutral wrist position while working. Workers are advised to reduce repetitive motions by taking frequent rest breaks, wearing wrist splints, and rotating tasks with other workers. Although there are no studies to prove that these programs prevent carpal tunnel syndrome, they are commonly recommended to prevent workplace injuries.