Isolated synovial sheath ...

A man in his late 20s who had been experiencing significant swelling in the ventral area of his left wrist for the previous six months and numbness in his index finger for the previous month was admitted to the hospital. The swelling began as a pea-sized growth and has since grown to the size of a lemon. Physical examination revealed that the swelling was uncomfortable to touch. It was firm, too hard in consistency. The skin above the oedema was normal, and the swelling was immobile. Following an ultrasound of the wrist, it was discovered that the median nerve was being compressed by excessively hypoechoic thickening of the tenosynovial sheath of the flexor tendons (figure 1). The joint spaces seemed normal despite the carpal bones' marrow oedema and a few cystic abnormalities in the capitate and hamate (figure 2A–D). The usual fibrillar pattern was gone, and the median nerve became thicker.