What is Carpal Tunnel Syndrome?
Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment syndrome, caused by compression of the median nerve as it passes through the carpal tunnel at the wrist, resulting in pain, numbness, tingling, and paresthesias in the thumb, index, middle, and radial half of the ring finger 1, 2.
Pathophysiology
The median nerve becomes compressed within the space-limited osteofibrous carpal canal at the wrist. This compression leads to nerve injury that can progress from mild intermittent symptoms to severe axonal damage with permanent sensory deficits and muscle weakness 3, 2.
Clinical Presentation
Patients typically experience:
- Numbness and tingling in the radial 3.5 digits (thumb, index, middle, and radial half of ring finger)
- Nocturnal paresthesias - a hallmark feature where patients wake at night with hand numbness
- Neuritic "pins-and-needles" pain in the affected fingers
- Hand weakness in advanced cases
- Thenar atrophy - a late finding that is highly specific but indicates severe, chronic disease 2, 4
The "flick sign" (patients shake their hands to relieve symptoms) is a characteristic clinical finding 5.
Epidemiology and Risk Factors
CTS affects up to 3.7% of the population and is the most common entrapment neuropathy worldwide 1, 6. It occurs more frequently in:
- Females
- Elderly patients
- Those with diabetes, pregnancy, morbid obesity
- Workers with repetitive wrist movements or exposure to vibrations
- Patients with certain genetic predispositions 3, 2
Diagnostic Approach
The diagnosis is primarily clinical - patients with typical symptoms in the median nerve distribution do not require additional testing 5, 4. However, confirmatory testing is useful in atypical presentations:
When to Order Additional Testing:
- Atypical symptoms requiring confirmation
- Diagnostic uncertainty
- Planning surgical intervention - electrodiagnostic studies determine severity and surgical prognosis 5, 4
Diagnostic Modalities:
- Electrodiagnostic studies (nerve conduction studies, needle electromyography) - confirm diagnosis and assess severity. An abnormal test rules in CTS, but a normal test does not exclude it 4
- Ultrasonography - highly sensitive and specific, can identify median nerve enlargement, space-occupying lesions, anatomic variants (bifid median nerve, persistent median artery), and has a confirmed role as a diagnostic tool 7, 1
- MRI - can identify nerve changes and anatomic variants but is typically not indicated for suspected CTS 7
Impact on Quality of Life
CTS significantly diminishes quality of life and imposes substantial costs on health systems due to its high prevalence, making it a priority for both clinical management and research 3, 8.
Important Caveat
Consider CTS mimics when evaluating hand symptoms - conditions from the hand to shoulder, including systemic and vascular sources, can present similarly. This is essential to avoid misdiagnosis 6.