What are the methods for diagnosing Carpal Tunnel Syndrome (CTS)?

From the Guidelines

Carpal tunnel syndrome can be effectively tested through a combination of clinical evaluation and electrophysiologic studies, with ultrasound or MRI without contrast being appropriate in selected circumstances. The diagnosis of carpal tunnel syndrome typically involves a physical examination to check for numbness, tingling, or weakness in the hand and wrist, particularly in the thumb, index, middle, and half of the ring finger 1. Provocative tests such as Tinel's sign, Phalen's test, and the carpal compression test can also be used to elicit symptoms.

Diagnostic Studies

Diagnostic studies provide objective evidence and include:

• Nerve conduction studies, which measure how quickly electrical impulses move through the median nerve
• Electromyography (EMG), which evaluates electrical activity in muscles
• Ultrasound or MRI without contrast may be used to visualize the carpal tunnel and identify structural abnormalities, as supported by recent studies 1

Imaging Studies

According to the most recent guidelines, when radiographs are normal or equivocal and a patient has persistent symptoms with an unclear diagnosis, MRI without IV contrast is usually appropriate 1. Additionally, ultrasound area of interest or MRI area of interest without IV contrast may be appropriate as the next imaging study when there is concern for carpal tunnel syndrome 1.

Recommendations

The most effective approach to testing for carpal tunnel syndrome is a combination of clinical evaluation and electrophysiologic studies, with imaging studies such as ultrasound or MRI without contrast being used in selected circumstances. This approach is supported by recent studies, including a 2024 study published in the Journal of the American College of Radiology, which found that ultrasound and MRI without contrast are highly sensitive and specific for the diagnosis of carpal tunnel syndrome 1.

Key Points

• Clinical evaluation and electrophysiologic studies are the primary methods for diagnosing carpal tunnel syndrome
• Ultrasound or MRI without contrast may be used in selected circumstances to visualize the carpal tunnel and identify structural abnormalities
• Recent studies support the use of ultrasound and MRI without contrast as effective diagnostic tools for carpal tunnel syndrome 1

From the Research

Diagnostic Tests for Carpal Tunnel Syndrome

• The diagnosis of carpal tunnel syndrome (CTS) can be made through a combination of clinical evaluation, provocative maneuvers, and electrodiagnostic studies 2, 3, 4, 5, 6
• Provocative maneuvers, such as the Phalen test and Tinel sign, have varying sensitivity and specificity for the diagnosis of CTS 2, 3, 5, 6
• The Phalen test and carpal compression test have the highest overall accuracy, while Tinel's nerve percussion test is more specific to axonal damage that may occur as a result of moderate to severe CTS 3
• Sensory evaluation of light touch, vibration, or current perception thresholds can detect early sensory changes, whereas 2-point discrimination changes and thenar atrophy indicate loss of nerve fibers occurring with more severe disease 3
• Electrodiagnostic studies, such as nerve conduction studies, can confirm the diagnosis of CTS, exclude other causes, and gauge severity for surgical prognosis 2, 5

Clinical Evaluation

• A clear history that elicits relevant personal and work exposures and the nature of symptoms can lead to a high probability of a correct diagnosis 3
• Hand diagrams and diagnostic questionnaires are available to provide structure to this process 3, 6
• The hand elevation test may be used in isolation and is superior to questionnaires and other physical signs in the clinical diagnosis of CTS 4
• Hypalgesia in the median nerve territory, classic or probable Katz hand diagram results, and weak thumb abduction strength are findings that best distinguish between patients with electrodiagnostic evidence of CTS and patients without it 6

Electrodiagnostic Studies

• Nerve conduction studies are useful for ruling in CTS, but a normal test does not necessarily exclude it 2
• Electrodiagnostic studies can encompass a variety of tests and are commonly used to assess the presence/severity of neuropathic changes and to preclude alternative diagnoses that overlap with CTS in presentation 3
• The pathophysiologic changes occurring with different stages of nerve compression must be considered when interpreting diagnostic test results and predicting response to physical therapy management 3