Carpal Tunnel Syndrome - Examination and Findings

Anatomy of the Carpal Tunnel

Symptoms (History)

• Nocturnal paresthesias - the cardinal symptom; pain/tingling waking patient at night
• Numbness or paresthesia in the thumb, index, middle, and radial half of ring fingers (median nerve distribution)
• "Flick sign" - patient spontaneously demonstrates a "shaking out" or flicking movement of the wrist when asked what they do at night for symptom relief; positive when this movement is demonstrated - Localization in Clinical Neurology 8e
• Forearm and elbow pain that is diffuse, poorly localized, and aching in nature; occasionally proximal shoulder pain
• Weakness or clumsiness of the hand
• Symptoms typically aggravated by sustained wrist flexion/extension (driving, holding a phone, typing)

Clinical Examination Findings

Inspection

• Thenar atrophy - wasting of the abductor pollicis brevis (APB) and opponens pollicis; this is a late/advanced sign seen with prolonged, severe compression - Bailey and Love's Short Practice of Surgery 28e
• Thenar atrophy reported in about half of patients who eventually require surgery - Campbell's

Motor Testing

• Weakness of thumb abduction (APB - abductor pollicis brevis) - most reliable motor sign
• Opponens pollicis weakness - often underestimated as patients recruit long flexor tendons during testing
• The lumbricals to fingers 1-2 are also innervated by the median nerve distally but are less clinically obvious

Sensory Testing

• Decreased sensation (hypoesthesia) in the thumb, index, middle, and radial ring finger
• Two-point discrimination >5 mm is an objective, quantifiable finding - one of the most useful physical examination maneuvers for diagnosis - Tintinalli's Emergency Medicine
• Sensory loss limited to fingertips is more common; may even be restricted to one side of a digit due to fascicular arrangement
• Thenar eminence skin sensation is preserved (palmar cutaneous branch exits proximal to the tunnel)

Provocative Tests

1. Phalen's Test (Wrist Flexion Test)

• Method: Hold the wrist in complete flexion (90°) for 30-60 seconds
• Positive: Reproduction of numbness or tingling in the median nerve distribution
• Sensitivity: ~74%; false-positive rate ~25%
• Most sensitive of the standard provocative tests
• Bradley and Daroff's Neurology in Clinical Practice; Campbell's Operative Orthopaedics 15e

2. Tinel's Sign (Nerve Percussion Test)

• Method: Light percussion over the median nerve at the volar wrist
• Positive: Tingling radiating into the hand in the median distribution
• Most specific but least sensitive of the standard tests
• Firestein & Kelley's Textbook of Rheumatology; Localization in Clinical Neurology 8e

3. Durkan's Carpal Compression Test (Most Accurate)

• Method: Direct pressure applied with thumbs (or a manometer-attached atomizer bulb) over the carpal tunnel for 30 seconds, with wrist in neutral position
• Positive: Reproduction of paresthesias
• Sensitivity: 87%; Specificity: 90% - more sensitive and specific than either Tinel or Phalen
• Considered the most sensitive provocative test when wrist is in neutral position - Campbell's; Miller's Review of Orthopaedics 9e; Bailey and Love's 28e

4. Gilliat-Wilson Cuff Compression Test

• A blood pressure cuff inflated above systolic pressure aggravates median paresthesias and pain
• Localization in Clinical Neurology 8e

5. Hyperextension of the Wrist (Reverse Phalen)

• May also aggravate paresthesias, though less commonly tested
• Localization in Clinical Neurology 8e

CTS-6 Diagnostic Scoring Tool

• Sensitivity 95% (vs. 91% for EMG/NCS or ultrasound)
• Specificity 91% (vs. 83% for EMG/NCS; 94% for ultrasound)
• Higher scores correlate with EMG/NCS severity

Investigations

Electrodiagnostic Studies (Gold Standard Confirmation)

• Distal motor latency >4.5 ms = abnormal
• Sensory latency >3.5 ms = abnormal
• EMG may show: increased insertional activity, positive sharp waves, fibrillations at rest, decreased motor recruitment, complex repetitive discharges
• NCS: reported ~90% sensitive and ~60% specific
• Caveat: Studies can be normal in symptomatic patients and abnormal in asymptomatic patients
• Not a predictor of functional recovery after release
• Most useful in atypical presentations, before surgery in compensable injury claims, and to exclude proximal lesions (adding EMG of cervical paraspinals and H-reflex/F-wave testing helps differentiate CTS from cervical radiculopathy or thoracic outlet syndrome)

Ultrasound

Screening Blood Tests

• Fasting glucose (diabetes)
• TFTs - hypothyroidism
• Rheumatoid factor / anti-CCP
• Consider: serum ACE (sarcoidosis), IGF-1 (acromegaly), serum protein electrophoresis (amyloid, myeloma)

Associated Conditions (Box 82.2)

Differential Diagnosis

• Cervical disc disease / radiculopathy (C6-C7)
• Thoracic outlet syndrome
• Diabetic or other peripheral neuropathies
• Pronator teres syndrome (proximal median nerve entrapment)
• Inflammatory conditions / autoimmune disorders

Summary of Exam Findings by Severity

Thenar atrophy, severe sensory loss, and active denervation on needle EMG are indications for surgical carpal tunnel release. - Bradley and Daroff's Neurology in Clinical Practice