Evaluation of bifid median nerve with sonography and MR imaging.

Bifid median nerve is an anatomic variation that may be associated with carpal tunnel syndrome. It is important for the surgeon to be aware of the existence of this condition preoperatively in order to plan the carpal tunnel release. We report the correlation between ultrasonographic findings and magnetic resonance imaging results in six patients with bifid median nerve, selected from a population of 294 patients with carpal tunnel syndrome, who were studied by ultrasonography using a high frequency transducer. Sonography showed two structures inside the carpal tunnel with the same pattern as the median nerve in all six patients. Magnetic resonance imaging confirmed the sonographic findings. The patients underwent open surgery, and a bifid median nerve was found. In conclusion, bifid median nerve is an anatomic variant that can be demonstrated ultrasonographically. It is important to be aware of this anomaly when planning carpal tunnel release surgery.