Anatomical Variations in the Pathway of the Median Nerve: A Gross Cadaver Study
Chika Okafor, MD1, Chukwuemeka Mbagwu, MD2 and Robert Wilson, MD1, (1)Howard University, Washington, DC, (2)Mount Sinai, New York, NY
Purpose and Significance: The median nerve may vary in its course throughout the hand, so a surgeon may inadvertently cut this "million dollar nerve", as lawsuit of cutting this nerve during carpal tunnel surgery have led to. The aim is to identify variations in the pathway of this nerve. The purpose is to prevent inadvertent severing of the median nerve. Methods: Two orthopaedic surgery residents dissected the upper extremities of 51 hands from 29 bodies of the institution's anatomy lab. Results: Opponens pollicis and abductor pollicis brevis received 100% median nerve innervation 100%. Adductor pollicis received twigs from the ulnar nerve 88% of the time. The flexor pollicis brevis received median nerve innervation 73% of the time, ulnar nerve innervation 2% of the time, and dual innervation 25% of the time from the deep branch of the ulnar nerve and recurrent motor branch of the median nerve. Conclusion: Variations in the pathway of the median nerve were uncovered. We identify a novel structure, termed the ansa thenaris, which may innervate the intrinsic muscle of the thumb in some patients. Because the ulnar nerve and median nerve may both contribute to thumb function when the ansa thenaris is involved, patients with this innervation pattern may benefit from conservative treatment before carpal tunnel release.
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