What is Carpal Tunnel Syndrome
Carpal tunnel syndrome is a compressive neuropathy caused by compression of the median nerve as it travels through the carpal tunnel at the wrist, resulting in pain, numbness, and tingling in the median nerve distribution (palmar aspect of the thumb, index and middle fingers, and radial half of the ring finger). 1
Anatomic and Pathophysiologic Basis
- The condition occurs when the median nerve is squeezed or compressed as it passes through the carpal tunnel, a narrow passageway in the wrist bounded by carpal bones and the flexor retinaculum 2
- The pathophysiology involves a combination of mechanical trauma, increased pressure within the carpal tunnel, and ischemic damage to the median nerve 2
- Key anatomic findings include enlargement and flattening of the median nerve, and bowing of the flexor retinaculum 3
Clinical Presentation
- Patients classically experience pain and paresthesias in the distribution of the median nerve, which includes the palmar aspect of the thumb, index and middle fingers, and radial half of the ring finger 1
- Symptoms typically include numbness and tingling in the affected fingers, with pain that may radiate proximally 2
- The condition is characterized by sensory and motor symptoms in the median nerve distribution 3
Epidemiology and Risk Factors
- Carpal tunnel syndrome is the most common entrapment neuropathy of the upper extremity and the most common of the chronic compressive neuropathies 1, 4
- Risk factors include obesity, monotonous wrist activity, pregnancy, genetic heredity, and rheumatoid inflammation 2
- The most frequent cause is idiopathic, meaning no specific underlying cause is identified 5
Important Clinical Pitfall
- Bilateral carpal tunnel syndrome without rheumatoid arthritis or known trauma may be an early sign of cardiac amyloidosis or other systemic conditions, and should prompt further evaluation 3, 6
- Proximal median nerve compression can mimic carpal tunnel syndrome symptoms and should be considered in the differential diagnosis when symptoms are atypical 7
Acute vs. Chronic Forms
- The chronic idiopathic form is most common, with symptoms that generally worsen over time, though spontaneous regression is possible 5
- Acute carpal tunnel syndrome is much less common and is more often directly related to fractures, fracture-dislocations about the wrist, hemorrhagic conditions, and vascular disorders, requiring urgent surgical intervention 4