Carpal tunnel syndrome caused by an anomalous muscle belly of the index finger lumbrical

Carpal tunnel syndrome is the most common neuropathy of the upper extremity. It usually occurs without any extrinsic cause; sometimes it is due to aberrant anatomy. A case of an anomalous first lumbrical muscle belly in a 52-year-old woman is described. This patient was operated on without success. During the first intervention, nothing abnormal was observed. Due to the persistence of symptoms, she was operated on again. In the second surgery, an anomalous first lumbrical muscle was detected and resected with a good clinical result. These rare anatomical situations can cause symptoms and should be explored and corrected.