Anomalous flexor superficialis indicis: two case reports and literature review

Derived from postmortem dissections, early descriptions of a muscle belly in the palm that served the index finger in the manner of the flexor digitorum superficialis were published by MacAlister (1868), Graper (1917), and Mainland (1927). In the English literature, we have found reports on only 15 clinical cases that involved the palm. Based on available information regarding sex, 12 patients were female and one was male. The anomaly involved the right hand in all cases and was bilateral in four of the female patients. We report two additional cases, of which one is considered the first bilateral case in a man with symptoms on the left side.