How to differentiate between carpal tunnel syndrome and cervical neuropathy?

Differentiating Carpal Tunnel Syndrome from Cervical Radiculopathy

The differentiation between carpal tunnel syndrome (CTS) and cervical radiculopathy requires a systematic approach combining specific clinical features, targeted physical examination findings, and confirmatory electrodiagnostic testing, as no single test or symptom reliably distinguishes between these conditions. 1

Clinical History: Key Distinguishing Features

Symptom Distribution Pattern

• CTS typically causes numbness and tingling in the thumb, index, middle, and radial half of the ring finger (median nerve distribution), often sparing the little finger 2
• Cervical radiculopathy produces symptoms in a dermatomal pattern corresponding to the affected nerve root (C5-C7 most commonly), which may include the entire hand or extend proximally up the arm 3
• Neck and shoulder pain radiating down the arm strongly suggests cervical radiculopathy rather than isolated CTS 4

Temporal Characteristics

• CTS symptoms classically worsen at night and may awaken patients from sleep, improving with hand shaking or position changes 2
• Cervical radiculopathy symptoms typically worsen with neck movements or positions that narrow the neural foramen 3

Provocative Factors

• CTS is aggravated by repetitive hand use, gripping, or wrist flexion/extension 5
• Cervical radiculopathy worsens with neck extension, rotation, or lateral bending toward the affected side 3

Physical Examination: Targeted Testing

Hand-Specific Tests for CTS

• Tinel's sign at the wrist (tapping over the median nerve produces paresthesias in median nerve distribution) 2
• Phalen's test (wrist flexion for 60 seconds reproduces symptoms) 2
• Thenar muscle atrophy in severe, chronic CTS 2
• Sensory loss limited to median nerve distribution (thumb, index, middle, radial half of ring finger) 5

Cervical Spine Tests for Radiculopathy

• Spurling's test (neck extension with rotation and lateral bending toward the symptomatic side reproduces radicular symptoms) 3
• Dermatomal sensory loss corresponding to specific cervical roots 3
• Myotomal weakness in specific muscle groups (C5: deltoid/biceps; C6: wrist extensors/biceps; C7: triceps/wrist flexors) 3
• Diminished or absent deep tendon reflexes (biceps for C5-C6, triceps for C7) 3

Important caveat: Physical examination findings have limited accuracy for diagnosing cervical radiculopathy, with systematic reviews showing poor correlation between clinical tests and imaging/surgical findings 3

Electrodiagnostic Testing: The Gold Standard

Nerve Conduction Studies

• Median nerve sensory conduction velocity <35 m/s or motor conduction velocity <57 m/s across the wrist confirms CTS 4
• Distal motor latency >4.0 ms is abnormal in CTS 4
• Comparing median nerve parameters to ulnar or radial nerve in the same hand increases diagnostic accuracy 5
• Normal nerve conduction studies across the wrist effectively rule out CTS 5

Electromyography (EMG)

• EMG of cervical paraspinal muscles and limb muscles identifies cervical radiculopathy by showing denervation in a myotomal distribution 3
• EMG can detect both conditions simultaneously (double crush syndrome) 4, 6

Critical point: Electrodiagnostic studies are the most sensitive and accurate method for confirming CTS and distinguishing it from cervical pathology 5

Imaging Considerations

When to Image the Cervical Spine

• MRI of the cervical spine is indicated when red flag symptoms are present: trauma, malignancy, infection, myelopathy, or progressive neurological deficits 3
• MRI should be obtained when clinical examination suggests cervical radiculopathy with dermatomal sensory loss, myotomal weakness, or reflex changes 3
• MRI findings must be correlated with clinical symptoms, as degenerative changes are common in asymptomatic individuals over age 30 and correlate poorly with neck pain 3

Imaging for CTS

• MRI or ultrasound of the wrist can confirm median nerve compression but is not routinely required when electrodiagnostic studies are positive 2

Double Crush Syndrome: A Common Coexistence

• 62% of patients with cervical radiculopathy also have CTS (double crush syndrome) 6
• Patients with both conditions show more severe electrodiagnostic abnormalities than those with CTS alone, with slower conduction velocities and lower amplitudes 4
• The presence of neck/shoulder pain with hand symptoms should raise suspicion for coexistent pathology 4
• Age is a significant risk factor, with double crush syndrome patients being approximately 11 years older (mean age 55) than those with isolated CTS (mean age 44) 6

Diagnostic Algorithm

1. Obtain detailed symptom history: distribution pattern, timing, provocative factors 1, 2
2. Perform targeted physical examination: hand-specific tests for CTS and cervical spine tests for radiculopathy 3, 2
3. Order nerve conduction studies and EMG as the definitive diagnostic test to confirm or exclude CTS and identify cervical radiculopathy 5
4. Consider MRI cervical spine if clinical examination or EMG suggests cervical radiculopathy, or if red flag symptoms are present 3
5. Recognize that both conditions may coexist, particularly in older patients with neck and hand symptoms 4, 6

The severity of CTS does not correlate with the severity of cervical radiculopathy when both are present, suggesting these may be independent processes rather than a true "double crush" mechanism 6