Carpal Tunnel Syndrome: Overview

Carpal Tunnel Syndrome: Overview

Carpal tunnel syndrome is a symptomatic compression neuropathy at the level of the wrist. What this means is there is compression of a nerve, namely the median nerve, inside the tunnel of the wrist, which leads to a number of symptoms.

Within this narrow tunnel, also known as the carpal canal, there are 9 robust tendons, and next to them the softer median nerve. These flexor tendons are covered by a synovial sheath that can thicken, causing a decreased space within the canal. The transverse carpal ligament, which is the roof of the carpal canal, may also become inflamed and thickened, and so the median nerve, being the softest structure within the carpal canal, can easily be compressed.

The median nerve innervates a large part of the hand and fingers. Hence, when compressed, the symptoms of numbness and tingling are commonly felt throughout. Typically, the thumb, index, and middle fingers and radial half, or towards the thumb side of the ring finger, are involved. The carpal tunnel can be seen here under the transverse carpal ligament. We can really appreciate how narrow this tunnel is. The transverse carpal ligament is the ligament the doctor cuts to relieve pressure of the compressed median nerve.

Carpal tunnel syndrome is very common and affects 0.1%-10% of the general population, with 12 million cases in the US currently. Several studies have shown that females are affected more commonly, especially around 55 to 60 years of age. It is so common, in fact, that approximately 600,000 cases require surgery annually in the United States. About 25% of those surgeries are achieved endoscopically with a small, single 1 cm incision.

Risk factors of a patient may include females, especially around menopause, obesity, diabetes, hypothyroidism, pregnancy, even due to a thickening synovium narrowing the carpal tunnel, and rheumatoid arthritis. Causes may be work-related by exposure to repetitive motions and vibratory tools. However, the strongest association is likely genetic.

There are many steps that can be taken to avoid carpal tunnel syndrome, especially by preventing strain on the wrists and to keep them in a neutral manner. Do not contort the wrists, take breaks often, and change hand positions when necessary.

Symptoms may vary depending on the severity of the disease. In the early stages, patients complain of symptoms such as radiating pain, numbness, paresthesias, or tingling in the hand and fingers with a gradual onset, especially at night. This is due to involvement of the sensory branch of the median nerve. Over time, patients report symptoms from involvement of the motor fibers of the median nerve as well. There is subjective weakness, clumsiness, severe numbness, and thenar muscle wasting or decreased muscle size of the thumb with severe loss of dexterity.

Symptoms are worse with typing, driving, biking, or doing activities that involve flexing or extending the wrist. Several tests can help diagnose carpal tunnel syndrome. None of these are diagnostic on their own, but more so as a combination of symptoms, signs, and diagnostic tests.

On physical examination, we inspect for muscle wasting and strength of thenar muscles to test the motor component of the median nerve. It is easily noticeable in a patient by comparing both palms together, as seen here. The late sign of muscle wasting signifies functional loss of thumb with inability to pinch or grasp objects.

Lastly, the most valid way to diagnose carpal tunnel syndrome is with a combination of these aforementioned clinical symptoms and signs, along with electrodiagnostic findings. A nerve conduction study is an objective test that provides information on the physiological health of the median nerve across the carpal tunnel. With these quick and effective tests to diagnose carpal tunnel syndrome, the doctor can provide the next steps, either by conservative or perhaps surgical measures, to ensure the patient adequately finds relief from their symptoms.