Causes of Carpal Tunnel Syndrome
Carpal tunnel syndrome is primarily caused by compression of the median nerve as it travels through the carpal tunnel in the wrist, resulting in characteristic pain, paresthesia, and sometimes weakness in the distribution of the median nerve. 1
Primary Causes
- Compression of the median nerve within the carpal tunnel is the fundamental pathophysiological mechanism 1, 2
- Increased pressure within the carpal tunnel leads to mechanical trauma and ischemic damage to the median nerve 2
Risk Factors and Associated Conditions
- Obesity contributes significantly to carpal tunnel syndrome development 2
- Repetitive or monotonous wrist activities can lead to inflammation and subsequent nerve compression 2
- Pregnancy is a known risk factor, likely due to fluid retention and hormonal changes 2
- Genetic predisposition plays a role in some cases of carpal tunnel syndrome 2
- Rheumatoid inflammation can cause tissue swelling within the carpal tunnel 2
- Bilateral carpal tunnel syndrome may be an early sign of systemic conditions or amyloidosis 3, 4
- Unexplained bilateral carpal tunnel syndrome (without rheumatoid arthritis or known trauma) may be associated with cardiac amyloidosis 5
Anatomical Factors
- Anatomic variants including bifid median nerve and persistent median artery can predispose to carpal tunnel syndrome 3
- Space-occupying lesions within the carpal tunnel can compress the median nerve 3
- Tendon pathology within the carpal tunnel may contribute to median nerve compression 3
Diagnostic Considerations
- Carpal tunnel syndrome is primarily diagnosed through clinical evaluation combined with electrophysiologic studies 6
- Characteristic findings include enlargement and flattening of the median nerve, and bowing of the flexor retinaculum 3
- Ultrasound can demonstrate median nerve enlargement and is highly sensitive and specific for diagnosis 3, 4
- MRI can show detailed anatomical changes but is typically not indicated for routine evaluation 4, 6
- Electrodiagnostic studies can confirm the diagnosis in atypical cases and gauge severity 1
Important Clinical Distinctions
- Proximal median nerve compression should be considered in the differential diagnosis of carpal tunnel syndrome 7
- Pronator syndrome and anterior interosseous nerve syndrome can present with similar symptoms 7
- Idiopathic carpal tunnel syndrome is the most common presentation, where no specific cause is identified 2
- Carpal tunnel syndrome is the most common entrapment neuropathy, affecting approximately 3-6% of adults 8