An additional muscle belly of the first lumbrical muscle.

Introduction: Lumbrical muscles play a vital role in the precision movements of the hand, along with the thenar, hypothenar and interossei muscles. The variation in the lumbrical muscle is clinically significant.

Case Presentation: During routine dissection of an adult male cadaver, we observed an additional muscle belly of the first lumbrical muscle took origin from the tendon of the flexor digitorum superficialis (FDS) to the index finger, close to the proximal margin of the flexor retinaculum.

Conclusion: The presence of such an additional muscle in the carpal tunnel should be considered in the aetiology of carpal tunnel syndrome (CTS).