Carpal tunnel syndrome is a condition affecting one of the main nerves in the wrist area. The carpal tunnel is a space created by the natural arch of the wrist bones. A thick band called the transverse carpal ligament creates a roof to the tunnel. This means that the size of the tunnel cannot change, as the bones and ligament act like solid walls. Nine tendons that bend the fingers and thumb and the median nerve pass through the tunnel. The median nerve provides feeling (sensation) to the skin of the thumb, index and middle fingers, as well as half the ring finger. The nerve also provides the communication line to the muscles at the base of the thumb (thenar muscles).
The most likely cause of carpal tunnel syndrome is extra pressure on the median nerve at the wrist inside the tunnel. This extra pressure can come from swelling (inflammation) of the contents inside the tunnel. When pressure results in nerve symptoms, it is called a compressive neuropathy. While the exact carpal tunnel syndrome causes are usually unknown and due to the patient’s personal anatomy, there are many factors that can contribute to the increased pressure or inflammation, including:
Even making a tight closed fist or holding the wrist in bent or extended positions can put increased pressure on the median nerve. A prolonged or constant fist or bend (like a fist during sleep, reading a book, or some other activities) may put enough pressure to cause the numbness/tingling. If the funny feeling in the fingers just began, this is easily resolved by moving the fingers back and forth and out of the position. If the pressure continues off and on for weeks to months, the symptoms may come on faster after the activity or wrist position is created. It may also take longer for the symptoms to go away after the activity stops. Eventually, symptoms can become constant.
Repetitive activities in the workplace with forceful or repetitive gripping or vibration can also increase symptoms. However, it is complicated to determine if the work activity is the main cause of the symptoms or if work is incidentally just aggravating a condition that is already present (unrelated to work). The determination of cause of symptoms requires experienced and specialized health care providers to provide an opinion, taking many factors into account.
There are some risk factors that increase the chances of getting carpal tunnel syndrome. For example, women are more likely than men to experience carpal tunnel syndrome. It is more likely to occur with aging. Each decade someone is alive, there are more people that experience carpal tunnel syndrome. Thus, it is rare in children and adolescents and more common in ages 40 and over. Carpal tunnel syndrome is more common in people with obesity, diabetes, alcohol addiction, fibromyalgia and hypothyroidism. If you have carpal tunnel syndrome, your children may be more likely to get it. Also, during pregnancy, hormonal changes and extra body fluid retention may add swelling and pressure into the tunnel.
While symptoms can sometimes be worse at night, sleep has not been shown to cause carpal tunnel. Some people get symptoms while driving a car. This is also not necessarily the primary cause of the problem. The wrist position during driving or sleep, for example, may simply aggravate the symptoms.
Some of the symptoms of carpal tunnel syndrome may include:
The main symptom of carpal tunnel syndrome is numbness and/or tingling in the thumb, index and middle fingers, and all or half of the ring finger (the side closest to the thumb). In most cases of carpal tunnel syndrome, the numbness/tingling comes on gradually. If mild, the symptoms may come and go for months or even years without worsening. The symptoms can come and go during the day or at night. The symptoms may vary based on time of day, activity or wrist position. Sometimes the fingers are numb, and other times there is normal feeling. If the condition becomes worse, the numbness may become constant. The speed of symptom worsening can vary from very gradual where it is hard to notice, or the symptoms may come on all of a sudden. In the most severe cases, the muscles at the base of the thumb become weak and shrink in size. Dropping things may happen from both the numbness and/or thumb weakness.
In some types of injuries where there is deformity from a fracture or dislocation or significant internal bleeding, carpal tunnel syndrome may come on rapidly. Because the pressure rises rapidly, the nerve does not have time to adjust. This often creates more severe symptoms with pain as a noticeable symptom, and treatment is more of an emergency. It the sudden and severe nerve pressure problem is linked to an injury, the recovery is more unpredictable and slower.
Discomfort or pain can also happen with gradual onset carpal tunnel syndrome. However, pain is typically not the first or main symptom. The pain from carpal tunnel syndrome usually only occurs after the numbness and tingling has started. The pain resolves when the numbness and tingling is alleviated. Shaking the hand or bending/straightening the fingers repeatedly may alleviate the numbness and tingling. The pain of carpal tunnel syndrome may be only in the hand or may be radiated to the forearm, even to the shoulder. It is important to understand that pain without median nerve finger numbness or tingling is NOT usually carpal tunnel syndrome.
The diagnosis of carpal tunnel syndrome is made in many patients based on their history of symptoms and a physical examination. It is important to know which fingers experience the numbness or tingling and which fingers do not. When performing the physical exam, your hand surgeon will perform sensation testing on the palm side and the back side of the fingers and hand. He or she may also perform sensory testing of the forearm and arm because finding numbness outside the median nerve area may suggest a different problem. The doctor may also perform some tests including the Phalen’s maneuver, the Tinel’s test, and a compression test. These tests are designed to increase pressure on the median nerve to cause your symptoms to appear. Electrodiagnostic studies (EMG) may also be used in the diagnosis. These provide evidence of nerve function or dysfunction. Also, they can help to find other causes of numbness which may have similar symptoms, such as diabetic neuropathy or cervical radiculopathy. Magnetic Resonance Imaging (MRI) and ultrasound studies are anatomic imaging tests that visualize the size of the median nerve and may also be used. Anatomic imaging tests are often helpful when other conditions are suspected like a ligament tear or tendinitis that may contribute to pain.
Therefore, it is possible that your doctor will diagnose you with a condition other than carpal tunnel syndrome. Other conditions that can cause numbness/tingling in the hand include compression conditions in the forearm, elbow, shoulder, or neck, fibromyalgia, myofascial pain syndrome and peripheral neuropathy.
The main goal of treatment is to reduce or remove the causes of increased nerve pressure. This should result in a decrease in symptoms. Some non-surgical treatment options may include:
Oral medications and injections are more effective when symptoms are present for a short period of time, infrequent and mild. Wrist splinting, mainly at night, keeps the wrist out of a bent position. Wrist splints are most helpful with symptoms that are affected by the hand or wrist position. Splints are also more helpful when the symptoms are mild and when symptoms have been present for a shorter period of time. However, splints have been shown to improve, but not cure symptoms, even when carpal tunnel is severe. It can also be useful to limit activities that bring on numbness and tingling.
Surgical release of the carpal tunnel ligament is one of the most effective treatments. It takes the extra pressure off the nerve immediately and reliably. There are several different surgical techniques to cut the transverse carpal ligament. By opening the ligament, there is more room for the tendons and the nerve to pass through the tunnel without pressure.
After carpal tunnel release surgery, your surgeon may recommend temporarily avoiding certain activities. Moving the fingers right away and frequently after a surgical procedure helps to limit stiffness, swelling, and adhesions. Adhesions are areas of scar tissue that can form and link the nerve to the tendons it rests on. If adhesions form, the moving tendon will pull on the nerve and may cause symptoms. Early, gentle finger and wrist motion can help avoid adhesions and encourage tendons and nerves to move separately.
The surgical scar and surrounding area may go through some mild changes in color, firmness and tenderness over the first several months. These changes are normal. Most scars won’t change much after four months. You may work with a hand therapist, who will give instructions on exercises and scar massage to get your hand function back to normal. Returning to work after carpal tunnel surgery is dependent upon each person’s symptoms, job demands and employer policies. In patients with less physically demanding jobs, they will be able to return to work in a few days, where other jobs may take weeks to safely return. Your surgeon and therapist will discuss the best recovery plan with you.
After surgery, most patients have very little pain at the incision site. Numerous scientific studies have shown surgical pain can be well-controlled with acetaminophen, non-steroidal anti-inflammatory drugs (NSAIDs) (like Ibuprofen), ice, elevation, early gentle finger and wrist motion, and limiting activity to things that are comfortable. Very rarely a patient may require a few doses of a stronger opioid pain medication within the first 2-3 days. It is very important to limit this type of strong pain medication to decrease the chance of becoming dependent on the medicine, having a tolerance build up, or having withdrawal symptoms when trying to stop it. Multiple medical organizations and state licensing boards have established guidelines and policies on safe prescribing of pain medication. Please discuss any concerns with your surgeon prior to any surgery to make sure everyone is on the same page and expectations can be clearly set and understood.
Better results will occur when carpal tunnel is recognized and treated earlier. This means seeking treatment when your symptoms are not severe, and they come and go. There will likely be complete return of feeling and muscle use after surgery. Relief may even be immediate.
However, if the symptoms are severe and constant when you seek treatment, the final result may be unknown. Your healing may be slow (six or more months). If there was permanent damage before surgery, you will likely still feel numbness. Unfortunately, there is no test to tell if the symptoms are reversible. If you lost use of your thumb muscle, that will likely persist, at least to some degree.
Visiting a hand surgeon as soon as your symptoms develop is key to receiving the best treatment and outcomes.
© 2021 American Society for Surgery of the Hand.
This content is written, edited and updated by hand surgeon members of the American Society for Surgery of the Hand. Find a hand surgeon near you.