Carpal tunnel syndrome is typically diagnosed through a combination of physical hand tests, a review of your symptoms, and in many cases an electrical nerve test. There’s no single test that catches every case, so doctors often layer several approaches to build confidence in the diagnosis.
Physical Tests Done in the Office
The first round of testing happens during your appointment, using simple hands-on maneuvers designed to compress or irritate the median nerve as it passes through your wrist. These take seconds to perform and don’t require any equipment.
Phalen’s test is one of the most common. Your doctor will ask you to hold the backs of your hands together with your wrists fully bent downward for about 60 seconds. If this position triggers tingling, numbness, or pain in your thumb, index, or middle fingers, the test is considered positive. It has a sensitivity of about 68% and a specificity of 73%, meaning it catches roughly two-thirds of true cases but also flags some people who don’t actually have carpal tunnel.
Carpal compression test (sometimes called Durkan’s test) involves your doctor pressing directly over the carpal tunnel at your wrist for up to 30 seconds. The goal is to temporarily increase pressure on the median nerve. If your usual symptoms appear, that’s a positive result. In its original study, this test performed better than Phalen’s, with 87% sensitivity and 90% specificity. Other research has found somewhat lower numbers (around 64% sensitivity, 83% specificity), but it’s still considered one of the more reliable office-based tests.
Tinel’s sign is the simplest: your doctor taps over the median nerve at your wrist. If it sends a tingling or electric shock sensation into your fingers, that’s positive. It’s a useful clue but less reliable on its own than the other two tests.
Your doctor will also check for weakness in the muscles at the base of your thumb and test whether you’ve lost sensation in specific fingers. These findings help gauge how advanced the compression may be.
The Symptom Profile Matters More Than You’d Think
The 2024 guidelines from the American Academy of Orthopaedic Surgeons gave a strong recommendation for a clinical scoring tool called CTS-6, which combines six specific findings: your symptom pattern, whether you wake up at night with numbness, results from Phalen’s and Tinel’s tests, loss of sensation, and thumb muscle weakness. Each item gets a score, and the total helps estimate how likely carpal tunnel is.
What’s notable is the guideline’s conclusion: strong evidence supports using this clinical scoring approach to diagnose carpal tunnel syndrome without automatically ordering electrical nerve testing or ultrasound. That doesn’t mean those tests are unnecessary. It means that for many patients, a thorough clinical exam can be enough, and the more advanced tests are best reserved for cases where the clinical picture is unclear or the scoring suggests a low probability.
Nerve Conduction Studies and EMG
When your doctor needs objective confirmation, nerve conduction studies (NCS) are the go-to test. This is the one most people picture when they think of carpal tunnel testing: small electrodes are placed on your hand and wrist, and brief electrical pulses are sent through the median nerve. The test measures how fast the electrical signal travels and how long it takes to reach your fingers or thumb muscles.
In carpal tunnel syndrome, the nerve signal slows down as it passes through the compressed area at the wrist. For example, the sensory signal normally travels faster than 42 meters per second through the wrist-to-palm segment. Slower speeds indicate the nerve is being squeezed. Doctors also measure how long it takes the signal to arrive (called latency). A longer delay confirms the nerve isn’t conducting normally.
The test takes 15 to 30 minutes. The electrical pulses feel like quick, sharp taps or mild shocks. They’re uncomfortable but brief, and most people tolerate the test without difficulty.
An EMG (electromyography) is sometimes done alongside nerve conduction studies. For this part, a thin needle electrode is inserted into muscles of the hand or forearm. It records the electrical activity of the muscle at rest and when you contract it. Healthy muscles are electrically silent when relaxed, so any spontaneous activity at rest suggests nerve damage has started affecting the muscle. EMG is particularly useful for two things: determining whether the nerve compression has progressed enough to cause actual muscle damage, and ruling out other conditions that mimic carpal tunnel, like a pinched nerve in the neck.
Accuracy Varies by Age
Nerve conduction studies are not perfect. Their accuracy shifts depending on your age. In patients 28 and younger, one study found sensitivity as low as 31%, meaning the test missed about 7 out of 10 cases in younger people, even when those patients had genuine carpal tunnel symptoms. In patients 72 and older, sensitivity jumped to 94%, catching nearly all cases. This means younger patients with clinical carpal tunnel can receive normal nerve conduction results and still have the condition. If that happens, your doctor may rely more heavily on symptoms and physical exam findings, or turn to ultrasound.
Ultrasound
Ultrasound has become an increasingly common diagnostic option. During the test, a technician places a probe on your wrist and measures the cross-sectional area of the median nerve. In carpal tunnel syndrome, the nerve swells just before it enters the tunnel. A cross-sectional area of 10 square millimeters or larger at the wrist is the standard diagnostic threshold, though this cutoff may be less reliable in men, whose nerves tend to be naturally larger.
The test is painless, takes only a few minutes, and has no electrical stimulation. It’s also useful for spotting structural causes of compression, like a cyst, swollen tendon, or anatomical variation that might be pressing on the nerve. The AAOS guidelines place ultrasound on equal footing with nerve conduction studies as a diagnostic tool when the clinical picture needs confirmation.
Tests That Aren’t Recommended
MRI is not recommended for diagnosing carpal tunnel syndrome. While it can show the median nerve and surrounding structures in detail, moderate-quality evidence shows it doesn’t reliably distinguish people with carpal tunnel from those without it. It’s expensive, time-consuming, and doesn’t add diagnostic value for this specific condition.
Upper limb neurodynamic testing, a physical maneuver that stretches the nerve from the neck through the arm, is also not recommended for diagnosis based on the same moderate-quality evidence.
Ruling Out Other Conditions
Part of the diagnostic process involves making sure your symptoms aren’t coming from somewhere else. The most common mimic is cervical radiculopathy, a pinched nerve in the neck that can send numbness and tingling down the arm into the hand. Two conditions can even coexist, which is called “double crush syndrome.”
To check for a neck problem, your doctor may perform a Spurling test (turning your head to one side and pressing down) or an arm squeeze test. Pain or tingling triggered by these neck-focused maneuvers points away from carpal tunnel and toward the cervical spine. The pattern of your symptoms also helps: carpal tunnel typically affects the thumb, index, middle, and half of the ring finger. Numbness that covers the entire hand, extends above the wrist, or involves the pinky finger suggests a different nerve or a different location of compression.
Nerve conduction studies and EMG are especially valuable here because they can pinpoint exactly where along the nerve the problem is occurring, whether that’s the wrist, the elbow, or the neck.