A two-trunked anatomical variance of the brachial plexus: A cadaveric case report

The brachial plexus is a network of nerves connecting five spinal nerve roots (C5-C8 and T1) and is responsible for transmitting motor and sensory signals to the upper limb. The ventral rami typically form three trunks, superior (C5-C6), middle (C7), and inferior (C8-T1), where each trunk channels motor and sensory information to specific upper limb regions. A unique variation of the trunks of the brachial plexus was discovered during a routine dissection of a male cadaver within an anatomy laboratory. We present a case of a prefixed, two trunk brachial plexus, formed by the fusion of the middle and inferior trunks, along with downstream variations in the terminal nerve branches. While anatomical variations of the brachial plexus are documented in the literature, fusion of the middle and inferior trunks are not commonly observed in human anatomy and subsequently not documented in the literature. Furthermore, we observed a prefixed plexus and anomalous communicating branches of the musculocutaneous nerve to the median nerve as additional features of the network. Altogether, understanding these variations is crucial for physicians, as it can affect surgical procedures and clinical presentations. • A rare brachial plexus variation with a characteristic superior and inferior trunk. • Two-trunk brachial plexus raises risk for surgical complications and thoracic outlet syndrome. • Prefixed plexus and anomalous terminal nerve branches add to complex nerve mapping.