The pisiform and trapezium at either end of the carpal arch are joined by the flexor retinaculum to form the carpal tunnel.
Within the tunnel are the tendons of most of the flexor muscles and the median nerve. The flexor retinaculum stop the muscle tendons bowing when the wrist is flexed.
Increased pressure within the carpal tunnel can cause carpal tunnel syndrome.
The initial cause is not always known but increased pressure leads to venous engorgement and nerve damage.
The patient will complain of abnormal sensation, normally pain and pins and needles, in the distribution of the median nerve. Tinel’s sign will be positive – tapping on the flexor retinaculum reproduces the pain and altered sensation. Later, the muscles of the thenar eminence will show wastage.
Carpal Tunnel Syndrome
Carpal Tunnel Syndrome is caused by compression of the median nerve in the carpal tunnel. Compression of the nerve typically causes numbness in the medial three and a half digits.
Most cases are ‘primary’. This means that there is no associated systemic disease or local structural lesion precipitating compression of the median nerve. Primary CTS is more common in middle-aged females and in persons whose occupations involve repetitive wrist and finger motion, such as typing. In many cases, no precipitating factor is identified.
Carpal Tunnel Syndrome is treated by bracing, steroid injection or in refractory cases carpal tunnel release wherein the carpal tunnel is split longitudinally to release pressure on the median nerve.
While there are several imaging modalities such as ultrasound and nerve conductive studies, Carpal Tunnel Syndrome is a clinical diagnosis.