Study on accessory thenar branches of median nerve in hand: its surgical importance in carpal tunnel syndrome

Abstract

Median nerve enters the palm through the carpal tunnel deep to flexor retinaculum of wrist. The median nerve gives off recurrent motor branch (thenar) just distal to flexor retinaculum to innervate thenar muscles of the hand. Objective: In present study the objective was to study the presence of accessory thenar branches and their side of origin. Materials and Methods: The study included 51 human cadaver hands at the Department of Anatomy, Mysore Medical College and Research Institute, Mysore during 2011-13. These specimens fixed in 10% formalin were finely dissected and variations were noted. Results: Out of 51 specimens, accessory thenar branches were present in 26 specimens (51%) i.e. 12 on right (23.5%) and 14 (27.45%) on left. Level of origin was observed within the retinaculum in 5 specimens (9.8%) on right and 2 specimens (3.9%) on left, distal to retinaculum in 7 specimens (13.7%) on right and 12 specimens (23.5%) on left side. Accessory thenar branch was originating from 1^st common digital nerve in 5 specimens (9.8%) on right and 1 specimen (1.96%) on left side, from radial proper digital nerve to thumb in 7 specimens (13.72%) on right, 13 specimens (25.49%) on left side. Conclusion: Knowledge of branching patterns and unusual variations helps in proper treatment of disorders of the median nerve. The possibility of multiple thenar innervations must be considered by hand surgeons in preoperative evaluation to reduce the hazards of iatrogenic injury or postsurgical complications.