Carpal Tunnel Syndrome (CTS) is caused by the compression of the median nerve as it passes through the narrow passageway in the wrist known as the carpal tunnel. This compression leads to tingling, numbness, and pain primarily in the thumb, index, middle, and a portion of the ring finger. Because these symptoms can overlap with other nerve or joint issues, a formal diagnosis requires a structured approach to confirm the median nerve is involved and to assess the severity of the entrapment.
Symptom Review and Medical History
The diagnostic journey begins with a detailed patient interview to understand the subjective experience of the condition. The doctor inquires about the location, severity, duration, and frequency of symptoms, focusing on the pattern of numbness and tingling. Symptoms that wake a person from sleep or occur while holding objects are highly suggestive of CTS.
Determining if symptoms affect the little finger is important, as the median nerve does not provide sensation to this digit; involvement there may suggest a different diagnosis. The interview also identifies potential risk factors, such as underlying health conditions (like diabetes or hypothyroidism) or occupational exposure to repetitive motions. This initial assessment establishes clinical suspicion.
Clinical Examination: Provocative Maneuvers
Once clinical suspicion is formed, the physical examination uses hands-on tests designed to temporarily increase pressure on the median nerve. These provocative maneuvers attempt to “provoke” the characteristic symptoms of tingling or numbness. These simple, non-invasive tests are performed in the clinic.
Phalen’s Maneuver involves pressing the backs of the hands together with the wrists fully flexed at a 90-degree angle. Holding this position for 30 to 60 seconds raises pressure within the carpal tunnel; reproduction of paresthesia in the median nerve distribution is a positive result. Tinel’s Sign is performed by lightly tapping directly over the median nerve at the wrist crease. A positive sign is an electric shock or tingling sensation that radiates into the fingers.
Durkan’s Test, also called the Carpal Compression Test, involves the examiner using their thumbs to apply firm pressure over the carpal tunnel for up to 30 seconds. The onset of numbness or tingling in the thumb, index, middle, and radial half of the ring finger is considered a positive finding. These clinical tests are valuable for initial screening but are not sufficient for a definitive diagnosis.
Definitive Diagnosis: Nerve Studies and Imaging
Specialized electrodiagnostic testing is used for objective confirmation and to assess severity. The Nerve Conduction Study (NCS) uses small electrical impulses to measure how quickly signals travel along the median nerve. Electrodes are placed on the skin, and a slowed conduction velocity across the wrist confirms the presence and location of nerve compression.
Electromyography (EMG) uses a fine needle electrode inserted into specific hand muscles controlled by the median nerve. This test measures the electrical activity of the muscles at rest and during contraction, helping assess for muscle damage in severe or prolonged cases of CTS. EMG is also useful for ruling out other conditions, such as nerve compression originating higher up the arm or neck.
Imaging studies assess surrounding structures or exclude other causes of pain. High-resolution Ultrasound provides a real-time visual of the median nerve, often showing characteristic swelling or flattening proximal to the compressed segment. While X-rays cannot diagnose CTS directly, they are ordered to rule out structural issues that mimic symptoms, such as fractures, arthritis, or bone spurs in the wrist.