What is the best test to diagnose a patient with intermittent hand pain and paresthesias, decreased sensation in the first through fourth digits, and an atrophied thenar eminence?

Diagnosis of Carpal Tunnel Syndrome in the Emergency Department

Percussion of the right volar wrist (Tinel's sign) is the most practical bedside test available in the ED to help diagnose this patient's carpal tunnel syndrome, though it should be combined with other provocative maneuvers for optimal diagnostic accuracy. 1, 2

Clinical Presentation Analysis

This patient presents with classic carpal tunnel syndrome (CTS):

• Intermittent pain and paresthesias in the median nerve distribution (first through fourth digits) 3, 1
• Thenar atrophy, which is a late finding and highly specific for CTS, indicating severe disease with motor involvement 3, 2
• Occupational risk factor (repetitive manual labor assembling electronics) 1

The presence of thenar atrophy indicates this is severe CTS with objective motor deficits, not mild disease 3.

Best ED Diagnostic Test

Percussion of the Right Volar Wrist (Tinel's Sign)

This is the correct answer for ED evaluation because:

• Tinel's sign involves tapping over the median nerve at the wrist to induce paresthesias in the median nerve distribution 1, 2
• It is more specific for axonal damage that occurs with moderate to severe CTS, which this patient clearly has given the thenar atrophy 2
• It can be performed immediately at the bedside without special equipment 1, 2
• Sensitivity is approximately 74%, with high specificity 4

Why Other Options Are Incorrect for ED Diagnosis

CT scan of the head:

• Completely inappropriate—this is peripheral nerve compression, not a central nervous system problem
• CT is not routinely used to diagnose CTS 5

Electromyography (EMG):

• While EMG/nerve conduction studies are the gold standard confirmatory test for CTS 6, 7, 3
• These are not typically available in the ED and require specialized equipment and trained technicians
• The American College of Radiology states that CTS is diagnosed primarily through clinical evaluation combined with electrophysiologic studies, but these are not emergency tests 6, 7
• EMG is used to confirm diagnosis in atypical cases, exclude other causes, and gauge severity for surgical prognosis 3

Ultrasound of the median nerve:

• While ultrasound is highly sensitive and specific for CTS diagnosis (measuring median nerve cross-sectional area ≥10 mm²) 5, 6, 8
• The American College of Radiology acknowledges US can identify anatomic variants and space-occupying lesions 5, 6
• However, US is not routinely available in most EDs for this specific diagnostic purpose
• It requires specialized technique and experience 8
• The American Academy of Orthopedic Surgeons reports limited evidence supporting routine ultrasound for CTS diagnosis 5, 6

Urine drug screen:

• Irrelevant to the diagnosis of CTS

Optimal Bedside Diagnostic Approach in the ED

Combine multiple provocative tests for best diagnostic accuracy:

1. Tinel's sign (percussion test): 74% sensitivity, high specificity for axonal damage 2, 4

2. Phalen's wrist flexion test: Maximum wrist flexion for 60 seconds to reproduce symptoms 1, 2

   • Sensitivity 61%, specificity 83% 4

3. Carpal compression test: Direct pressure over the median nerve 2, 4

   • The Phalen's and carpal compression tests have the highest overall accuracy 2

4. Combined wrist flexion with median nerve compression: Optimal cut-off time of 20 seconds gives sensitivity 82% and specificity 99% 4

   • This combined test has significantly better positive predictive values (99% at 50% prevalence) than other provocative tests 4

Critical Management Point

This patient requires urgent surgical referral, not just ED diagnosis:

• The presence of thenar atrophy indicates severe CTS with objective motor deficits 3
• Patients with severe CTS, including objective weakness or sensory deficits, should be offered surgical decompression 3
• The American College of Surgeons states that surgical decompression is the most effective treatment for CTS, especially for moderate to severe cases 7

Common Pitfalls to Avoid

• Do not delay surgical referral waiting for electrodiagnostic studies in a patient with obvious thenar atrophy 3
• Do not rely on a single provocative test—combine multiple maneuvers for better diagnostic accuracy 2, 4
• Do not order imaging studies (CT, MRI) routinely for CTS diagnosis in the ED—these are not indicated 5, 6, 7