How do you diagnose Carpal Tunnel Syndrome (CTS)?

How to Diagnose Carpal Tunnel Syndrome

Carpal tunnel syndrome is diagnosed primarily through clinical evaluation combined with electrophysiologic studies, with imaging reserved only for selected circumstances when the diagnosis remains unclear. 1

Clinical Evaluation

Patient History

• Pain and paresthesias in the median nerve distribution (palmar aspect of thumb, index and middle fingers, and radial half of ring finger) are the cardinal symptoms 2
• Nocturnal symptoms are characteristic, though they have limited diagnostic value when used alone 3
• Ask specifically about activities involving repetitive wrist movements, vibrating tools, or high-force hand use 4, 5
• Inquire about predisposing conditions: obesity, pregnancy, diabetes, thyroid disease, or rheumatoid arthritis 4

Physical Examination Findings

The most diagnostically valuable physical findings are:

• Hypalgesia (reduced pain sensation) in the median nerve territory (LR 3.1) - this is the single most useful physical finding 3
• Weak thumb abduction strength (LR 1.8 when present; LR 0.5 when normal, arguing against CTS) 3
• Classic or probable Katz hand diagram results (LR 2.4) - where patients mark their symptom distribution on a hand diagram 3
• The flick sign - patients demonstrate a flicking motion of the hand to relieve symptoms 2, 3

Traditional tests have limited diagnostic value:

• Phalen maneuver and Tinel sign have little diagnostic accuracy and should not be relied upon alone 3
• Thenar atrophy, two-point discrimination, vibratory testing, and monofilament testing are not diagnostically useful 3

Electrodiagnostic Studies

Obtain nerve conduction studies when:

• Clinical and/or provocative tests are positive AND surgical management is being considered 6
• Thenar atrophy is present 6
• Persistent numbness exists 6
• The diagnosis is atypical or unclear 2

Do not obtain electrodiagnostic studies when:

• Symptoms are typical and mild, and conservative management is planned 2

The testing protocol should follow American Academy of Neurology/American Association of Neuromuscular and Electrodiagnostic Medicine guidelines 6

Imaging Studies

Ultrasound may be used to:

• Measure median nerve cross-sectional area at the carpal tunnel (highly sensitive and specific) 1, 7
• Evaluate persistent symptoms after carpal tunnel surgery 1
• Clarify diagnosis when clinical and electrodiagnostic findings are discordant 1

MRI without contrast may be appropriate in selected circumstances with unclear diagnoses, but is typically not indicated 1

Do NOT routinely order:

• CT, CT arthrography, bone scan, or radiographic arthrography for suspected CTS 1
• MRI for typical presentations 1, 6

Laboratory Testing

Avoid routine laboratory testing in patients with typical carpal tunnel syndrome, as it generates more false positives than true positives 1

Consider laboratory evaluation only when:

• Atypical features suggest systemic disease (HbA1c, TSH, vitamin B12, vitamin B6, folate, serum protein electrophoresis) 1
• Signs of systemic inflammatory or autoimmune conditions exist (ANA, ESR, CRP, ANCA, hepatitis serologies, HIV) 1

Common Pitfalls to Avoid

• Do not rely on Tinel or Phalen signs alone - they have poor diagnostic accuracy 3
• Do not skip electrodiagnostic testing before surgery - it confirms diagnosis, determines severity, and helps establish surgical prognosis 2, 6
• Do not order imaging for typical presentations - clinical evaluation with electrodiagnostic studies is sufficient 1, 6
• Do not attribute symptoms to occupation without excluding intrinsic factors like obesity, diabetes, or thyroid disease first 5