Overview of Electrodiagnostic Evaluation of Carpal Tunnel Syndrome
Carpal tunnel syndrome (CTS) is a common condition that affects about 90% of people with nerve problems in a specific area, and it often comes up when doctors are checking the electrical activity of your muscles and nerves. About 3.8% of people in general have it. Women get it more than men and the chance of getting it goes up as you age, usually between 40 and 60 years old. It’s also more likely to happen if you have certain health conditions like an underactive thyroid (hypothyroidism), diabetes, rheumatoid arthritis, gout, swelling in your limbs (peripheral edema), acromegaly (a hormone disorder), tumors, or have had an injury. Pregnant people are also at risk. If your job involves repeated hand movements or strong grips, you could also be at risk of developing CTS.
People with CTS usually note numbness, weakness, and a prickly or pins-and-needles feeling (paresthesias) in the thumb, index finger, middle finger, and the part of the ring finger closest to the thumb. The base of your thumb, on the palm side, won’t be affected because a different nerve branch, which doesn’t go through the wrist’s small tunnel, gives it feeling. Another nerve branch that does pass through the tunnel powers certain thumb muscles. You might find that your symptoms get worse at night or when making repeated hand movements, especially if you need to bend (flex) your wrist a lot.
The symptoms can be grouped into three stages, depending on how bad they are. In stage 1, you might wake up often at night because your hands and fingers are tingling. This sensation might last until the morning and make your hands stiff. In stage 2, you might have the same symptoms during the day too. You may also notice some trouble with motor function, like dropping things from your hands. In stage 3, the final stage, the muscles at the base of your thumb may have wasted away (atrophy), and surgery to relieve pressure might not work very well.
Anatomy and Physiology of Electrodiagnostic Evaluation of Carpal Tunnel Syndrome
The carpal tunnel is a narrow passageway in the wrist, structured by bones and a firm band that covers the top of it called the transverse carpal ligament. This tunnel is full of nine tendons that control finger and thumb movements, as well as the median nerve. The median nerve gives sensation to the first three and half fingers. Carpal Tunnel Syndrome (CTS) develops when there isn’t enough space for everything inside the tunnel, applying pressure on the median nerve.
Frequently, damage to the nerves comes before damage to the parts that control movement. Various elements can contribute to the development of CTS. Persistent force can result in nerve injury due to the loss of the protective coating around the nerve. Lasting scarring of the outer layer of the nerve can lead to a thickening or scarring process called fibrosis. Changes in the lining of the joints, called synovial tissue, can increase the size of the canal and put pressure on the median nerve. Inflammation, or swelling, can also occur due to an increase in certain chemicals that control blood vessel function and pain.
Why do People Need Electrodiagnostic Evaluation of Carpal Tunnel Syndrome
Diagnosing Carpal Tunnel Syndrome (CTS) typically starts with your doctor asking about your symptoms and examining your hand and wrist. To help with this process, they may perform tests like Tinel’s and Phalen’s. These tests involve certain hand movements that can trigger the symptoms of CTS.
If you have minor symptoms and no other health issues seem to be causing them, further investigation usually isn’t needed. But if your symptoms are severe, like weakness, loss of feeling, or difficulty doing everyday tasks, your doctor may recommend a type of test called a nerve conduction study (NCS). This test checks the health of the nerves in your hand and wrist by measuring how well they carry electrical signals.
Although an NCS is the most reliable way to diagnose CTS, the test isn’t perfect. Sometimes it shows CTS in people who don’t have symptoms, or fails to show CTS in people who do have symptoms.
In some cases, your doctor might use other ways to help diagnose CTS. For example, an ultrasound can measure the size of the median nerve in your hand and wrist. And a type of scan called magnetic resonance imaging (MRI) can show if there’s something unusual about the nerve.
When a Person Should Avoid Electrodiagnostic Evaluation of Carpal Tunnel Syndrome
Carrying out electrical diagnostic tests on patients with Carpal Tunnel Syndrome (CTS) can be tricky in certain circumstances. Here’s why: The use of a test that involves inserting needles into the muscles, known as an electromyography (EMG), can be risky for people who have severe blood clotting problems or too few platelets, which are cell fragments that help stop bleeding. This might be the case if there are less than 50,000 platelets in each microliter of their blood.
Some experts believe that a certain measure of the blood’s ability to clot, known as the international normalized ratio (INR), should not be above 1.5 to 2.0. If it is, they might not choose to conduct an EMG. However, because the rate of serious bruising during an EMG for CTS is typically low, others feel it’s generally safe unless the INR value is above the normal range.
It’s also important to avoid inserting needles into areas where there’s an ongoing infection. Nerve conduction studies (NCS), which test how well the nerves are working, tend to be safe for patients who have modern bipolar cardiac devices implanted. These devices help regulate the heart’s rhythm. However, it’s generally recommended to not conduct NCS tests on people who have wires pacing their heart externally. And for patients with a pacemaker, the electrical stimulation shouldn’t be done directly or near the device itself to avoid complications.
Equipment used for Electrodiagnostic Evaluation of Carpal Tunnel Syndrome
An EMG machine is a device used to measure the electrical activity of muscles. This machine requires various equipment, which includes:
Surface electrodes – These can either be a disk or ring shape. They are used to pick up the electrical signals from your muscles. You have active electrodes, reference electrodes, and ground electrodes.
Needle electrodes – These are small needles that are inserted directly into the muscles to measure their activity more accurately.
Amplifiers – These devices magnify the signals from the muscles, making them easier for the doctor to read and interpret.
Filters – These are used to remove unwanted signals, making the results clearer.
Alcohol pads – They are used to clean your skin before the electrodes are put on or needles are inserted. This keeps the test safe and reliable.
Tape – This is used to secure the electrodes to your skin, making sure they don’t move during the test.
Who is needed to perform Electrodiagnostic Evaluation of Carpal Tunnel Syndrome?
A technician and a clinician, who might be a specialist known as a physiatrist, are involved in your care. A technician can be someone who conducts or assists in specific technical tasks. They could be involved in taking certain tests or operating specific medical equipment.
A ‘physiatrist’ or clinician is a medical professional with specific training in physical medicine and rehabilitation. This type of doctor helps patients who have conditions that affect their physical function and quality of life. They work with you to create a personalized treatment plan to help improve your quality of life. So, you may see these types of professionals during your health care journey.
How is Electrodiagnostic Evaluation of Carpal Tunnel Syndrome performed
Before any diagnostic tests are performed, it’s essential to go through your medical history and carry out a physical examination. The healthcare professional conducting the test will explain why you need to be tested for Carpal Tunnel Syndrome (CTS) and give you a rundown of the tests needed. This is called electrodiagnostic testing.
It’s critical for the healthcare professional to thoroughly discuss the potential positives and negatives of the examination with you, so you can understand what to expect. Written consent from you is also necessary before the tests. Ideally, the tests should be done on at least two body parts, and involve both sensory (ability to feel) and motor (ability to move) nerve function studies as well as an electromyographic (EMG – a test that measures the electrical activity of your muscles) needle test in both upper (proximal) and lower (distal) muscles. This comparison helps make a more accurate diagnosis.
Your limbs should ideally be warm, at or above 32 degrees Celsius because coldness can cause incorrect test results by making the nerve signals seem slower or weaker than they actually are. To minimise any electrical disturbance that might affect the test results, a special filter called a notch filter should be used. To further reduce potential electrical interference, all unnecessary machines should be turned off, including unplugging the bed if the test is conducted in a hospital.
Possible Complications of Electrodiagnostic Evaluation of Carpal Tunnel Syndrome
Electrodiagnostic studies, tests that measure the electrical activity of your muscles and nerves, are generally safe procedures. Just like any medical procedure, there’s a small chance of complications such as bleeding or infection, particularly when needles are used in the test. You might feel some mild discomfort or slight pain during the process. This is particularly true when the test involves the abductor pollicis brevis, which is a muscle in your hand that helps you move your thumb.
What Else Should I Know About Electrodiagnostic Evaluation of Carpal Tunnel Syndrome?
Doctors use what are called sensory nerve conduction studies to understand the cause of symptoms like tingling or pain in the hand, which can be a sign of a condition called Carpal Tunnel Syndrome (CTS). They measure a type of electrical signal called Sensory nerve action potentials (SNAPs) which often change first if you have CTS. They compare the measurements of these signals in two places on your hand – the mid palm, and an area past the tunnel in your wrist where the median nerve is getting squeezed.
If they find the speed these signals are traveling less than 50 meters per second across the area in your wrist, or if they see a difference larger than 10 meters per second between the speed of the signals at the two sites they looked at on your hand, it suggests CTS. A drop of more than 50% in the strength of the signals across the area in your wrist also points to CTS.
They can check for CTS more accurately by also comparing these signal measurements between some of the main nerves in your hand, including the median, ulnar, and radial nerves. This approach is really helpful if you have symptoms of CTS, but the first test of the median nerve did not show it. They can be sure about the diagnosis as the median nerve is the one that passes through the problem area in your wrist and any slowing in its signals would be because of it. This comparison increases the accuracy of the test from 75% to 95%. If they find a difference in the time it takes for signals to pass through these nerves of about 0.4 to 0.5 seconds, it’s a sign of CTS.
They also do motor nerve conduction studies where they look at other types of electrical signals produced by your muscles. If they find it takes those signals more than 4.2 milliseconds to travel, it can be a sign of CTS. They again compare these to the ulnar nerve to be sure there’s no general motor nerve issue. If they see a decrease in the signal strength during the test, it could show a problem with the median nerve, or even a block in nerve signals across the area in your wrist, which is CTS.
Doctors usually don’t assess what are called ‘late responses’ because they don’t give a lot of information and the sensory and motor nerve studies provide a better evaluation.
Another test doctors use is the Electromyography (EMG) – a technique used to evaluate nerve and muscle function. They perform this test mainly to see if there is any damage to the nerve that supplies the muscle in your thumb that helps it move away from your palm, which might be the case in CTS. If that’s indeed the case, they also test other muscles supplied by the same nerve to see if the issue is not just in your wrist. It’s also possible that the signals are being blocked along the tunnel in your wrist, causing a decrease in the ability of your thumb’s muscle to work efficiently.
