Carpal Tunnel Syndrome (CTS) occurs when the median nerve, which travels through a narrow passage in the wrist, becomes compressed. This compression generates the characteristic symptoms of numbness, tingling, and pain in the hand and fingers. Because CTS symptoms can mimic other conditions, such as a pinched nerve in the neck, doctors must perform specific tests to confirm the diagnosis and assess severity. The diagnostic process combines evaluating symptoms, performing manual physical tests, and using specialized electrical or imaging studies for confirmation.
Recognizing Symptoms and Preliminary Self-Checks
The first indication of carpal tunnel syndrome is a distinct pattern of sensory changes in the hand. This involves numbness, tingling, or a “pins and needles” sensation affecting the thumb, index finger, middle finger, and the thumb-side half of the ring finger. The small finger is generally unaffected because its sensation is controlled by the ulnar nerve.
Symptoms often intensify at night, frequently waking people from sleep, and are aggravated by repetitive wrist movements or sustained gripping. Many individuals instinctively try to relieve the discomfort by shaking or “flicking” their hand. This action, known as the “Flick sign,” provides temporary relief and strongly indicates median nerve irritation.
Observing these specific symptoms and their distribution suggests the need for a professional evaluation. These observations are not a formal diagnosis but indicate that a clinical assessment is required to determine the cause of the nerve irritation.
Clinical Physical Assessment Maneuvers
During a physical examination, doctors perform specific maneuvers intended to temporarily increase pressure on the median nerve, thereby attempting to reproduce the patient’s symptoms. A positive result on any of these tests strongly supports the clinical suspicion of carpal tunnel syndrome.
One widely used test is Tinel’s Sign, where the physician gently taps directly over the median nerve at the wrist. A positive result occurs if this tapping causes a tingling, “electric shock,” or “pins and needles” sensation to shoot into the fingers supplied by the median nerve.
Another common test is Phalen’s Maneuver, which requires the patient to hold their wrists in a position of forced flexion, pressing the backs of their hands together. Holding this position for 30 to 60 seconds is considered a positive result if it brings on the characteristic numbness or tingling.
The Durkan’s Test, or Median Nerve Compression Test, is often considered the most sensitive clinical maneuver. The healthcare provider applies direct, firm pressure with a thumb over the carpal tunnel. If the patient’s symptoms are reproduced within 30 seconds of sustained pressure, the test is considered positive for median nerve compression.
Definitive Neurological and Imaging Studies
To confirm the diagnosis, determine the severity of nerve damage, and rule out other conditions, physicians often rely on electrodiagnostic testing.
Nerve Conduction Studies (NCS)
NCS are the foundation of this testing and are performed by applying small electrical shocks to the nerve at various points along the arm. The test measures how quickly the electrical signal travels down the nerve. A significant slowing of the signal across the wrist indicates that the median nerve is being compressed in the carpal tunnel.
Electromyography (EMG)
Electromyography (EMG) is often performed with NCS, especially in more severe cases or when an alternate diagnosis is suspected. This test involves inserting a fine needle electrode into the small muscles at the base of the thumb controlled by the median nerve. The EMG assesses the electrical activity within the muscle both at rest and during contraction, which helps identify chronic damage or degeneration affecting muscle function.
Imaging Studies
Imaging studies play a secondary role in the diagnostic process. An X-ray is sometimes used to exclude other bony causes of wrist pain, such as a fracture or arthritis, but it cannot diagnose the nerve compression itself. Ultrasound is an increasingly utilized imaging modality that can visualize the median nerve. It can objectively confirm the diagnosis by measuring an enlargement of the median nerve’s cross-sectional area at the wrist, which is a direct sign of swelling and compression.