Carpal tunnel

Cause, clinical and ultrasound findings

• Carpal tunnel syndrome results from compression of the median nerve at the level of the wrist due to abnormal anatomy (thick retinaculum, accessory muscles, etc.), systematic conditions (diabetes, pregnancy, etc.) and space-occupying lesions (flexor tendon tenosynovitis, ganglia, etc.).

• Symptoms include numbness and burning pain of the thumb, the index and middle fingers and on the radial side of the ring finger; motor deficit and wasting of thenar muscles (in long-standing cases) may also be present.

• Ultrasound findings within the median nerve may include an abrupt notch at the level of pressure, proximal swelling (cross-sectional area >10 mm ² ), distal flattening (namely hourglassing) and a hypoechoic appearance with a loss of fibrillar echostructure. Occasionally neovascularity is seen in the median nerve. The transverse ligament may show increased convexity and thickening.