PURPOSE: Knowledge of the unusual arrangement of the flexor pollicis longus (FPL) muscle is important as the variable tendon may be a rare cause of carpal tunnel syndrome. METHODS: During a routine dissection at the Department of Anatomy, an unusual formation of the FPL muscle was observed in a formalin embalmed Central European cadaver. RESULTS: This report presents a variation of the FPL muscle, where the muscle split and formed a separate accessory head inserting into the first lumbrical muscle. Moreover, a tendinous interconnection was present between the FPL muscle tendon and the tendon of the aberrant muscle head. CONCLUSION: The cases described by previous literature, concerning the Linburg-Comstock variation or the accessory head of the first lumbrical muscle originating from the FPL muscle, are closest to the present case. Such variation has a clinical significance ranging from the functional limitation of the thumb and index finger movement to the potential median nerve compression.

Clinic of Trauma Surgery Masaryk Hospital Socialni Pece 3316 12A 400 11 Usti nad Labem Czech Republic

Department of Anatomy 2nd Faculty of Medicine Charles University Plzenska 130 221 150 06 Prague 5 Czech Republic

Department of Health Care Studies College of Polytechnics Tolsteho 16 586 01 Jihlava Czech Republic

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