Unilateral Presence of a Four-Headed Musculus Biceps Brachii: A Complex Anomalous Presentation on Upper Limb Dissection

International Journal of Anatomy and Physiology | Vol. 15, No. 9, September 2026 | pp. 425–436

DOI: 10.46882/2026/IJAP/000203

Article Type: Case Report

Title: Unilateral Presence of a Four-Headed Musculus Biceps Brachii: A Complex Anomalous Presentation on Upper Limb Dissection

Names of Authors: Carlos J. Gómez¹, María L. Ortega²

Authors’ Affiliations: ¹Department of Morphological Sciences, Faculty of Medicine, University of Valencia, Valencia, Spain; ²Department of Orthopaedic Surgery, Clinical University Hospital of Valencia, Valencia, Spain

Abstract:
The musculus biceps brachii commonly possesses long and short heads originating from the scapula. Variations in the number of accessory heads can lead to misinterpretations on magnetic resonance imaging (MRI) and present potential nerve compression syndromes. During routine educational dissection of a 68-year-old male cadaver, a rare case of a four-headed biceps brachii muscle was identified unilaterally on the right arm. In addition to the standard long and short heads, two distinct accessory heads were discovered. The third head originated from the anteromedial shaft of the humerus, directly inferior to the insertion of the coracobrachialis muscle. The fourth head arose from the medial intermuscular septum, adjacent to the brachialis muscle origin. Both accessory muscle slips descended distally to insert directly into the posterior aspect of the common bicipital tendon. Morphometric analysis showed that the third and fourth heads measured 84.5 mm and 62.4 mm in length, respectively. The musculocutaneous nerve passed beneath the third head and directly over the fourth head, creating a potential entrapment point. The contralateral limb displayed standard bicipital anatomy. This report highlights a multifaceted muscular anomaly that surgeons should note during anterior arm exposures or while managing unexplained proximal forearm weakness.

Keywords: Biceps Brachii, Accessory Heads, Muscular Variation, Musculocutaneous Nerve, Upper Limb Dissection

Manuscript Timeline: Received: August 20, 2026; Revised: September 15, 2026; Accepted: September 25, 2026; Published: September 30, 2026

Citation: Gómez C.J., & Ortega M.L. (2026). Unilateral Presence of a Four-Headed Musculus Biceps Brachii: A Complex Anomalous Presentation on Upper Limb Dissection. International Journal of Anatomy and Physiology, 15(9), 425–436. DOI: 10.46882/2026/IJAP/000203

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