What are the steps to diagnose carpal tunnel syndrome in a patient, particularly a woman between 40 and 60 years old with a history of repetitive hand use or certain medical conditions like diabetes or thyroid disorders?

Diagnosing Carpal Tunnel Syndrome

Carpal tunnel syndrome is diagnosed primarily through clinical evaluation combined with electrophysiologic studies, with imaging reserved only for atypical presentations. 1, 2

Clinical Evaluation

History

Obtain specific details about the following symptoms in the median nerve distribution (palmar aspect of thumb, index and middle fingers, and radial half of ring finger): 3

• Pain and paresthesias that are classically nocturnal 3, 4
• Flick sign: Patient shakes or flicks hand to relieve symptoms 3
• Duration of symptoms (shorter duration <1 year predicts better surgical outcomes) 1
• Occupational history of repetitive hand/wrist activities 4

Physical Examination

Perform the following specific tests: 5

• Hypalgesia testing in median nerve territory (LR 3.1) - most useful finding 6
• Thumb abduction strength testing: Weak strength supports diagnosis (LR 1.8), normal strength argues against it (LR 0.5) 6
• Katz hand diagram: Have patient mark symptom distribution; classic/probable pattern supports diagnosis (LR 2.4), unlikely pattern argues against it (LR 0.2) 6
• Sensory examination for small-fiber (pinprick, temperature) and large-fiber function (vibration with 128-Hz tuning fork) 7

Note: Traditional tests like Phalen and Tinel signs have little diagnostic value and should not be relied upon. 6

Electrodiagnostic Studies

Obtain electrodiagnostic testing when clinical examination is positive AND surgical management is being considered. 5

• Follow American Academy of Neurology/American Association of Neuromuscular and Electrodiagnostic Medicine guidelines 5
• Mandatory before surgery to determine severity and surgical prognosis 3, 5
• Also obtain when thenar atrophy or persistent numbness is present 5
• Not routinely needed for typical presentations managed conservatively 1

Imaging

Ultrasound may be used in selected circumstances: 1, 2

• When clinical diagnosis is unclear despite symptoms 1
• Measures median nerve cross-sectional area with high sensitivity and specificity 1, 2
• Useful for evaluating persistent symptoms after surgery 1

Do not routinely order MRI, CT, or other advanced imaging for typical carpal tunnel syndrome. 5

Laboratory Testing

Do not perform routine laboratory testing for typical carpal tunnel syndrome, as it generates more false positives than true positives. 1

Consider targeted testing only when atypical features suggest systemic disease: 1

• HbA1c (diabetes)
• TSH (thyroid disorders)
• Vitamin B12, B6, folate
• Serum protein electrophoresis with immunofixation

Additional autoimmune/inflammatory markers (ANA, ESR, CRP, ANCA) only if signs of systemic disease are present. 1

Differential Diagnosis Considerations

Exclude other causes of neuropathy in patients with diabetes or atypical presentations: 7

• Diabetic peripheral neuropathy (assess with 10-g monofilament for protective sensation) 7
• Cervical radiculopathy
• Polyneuropathy from toxins, medications, vitamin deficiencies 7
• Shoulder-hand syndrome in stroke patients 2