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Middle Trunk of Brachial Plexus
Nervous System

Middle Trunk of Brachial Plexus

Truncus medius plexus brachialis

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Quick Facts

Origin: C7 root of the brachial plexus.

Course: In the neck, it runs laterally between the anterior and middle scalene muscles, through the posterior triangle towards the clavicle.

Branches: Anterior division of the middle trunk, posterior division of the middle trunk.

Supply: Sensory and motor innervation. Supplies the nerves branching off the lateral cord, and the thoracodorsal and radial nerves of the posterior cord. Sensory to the posterior arm, forearm, and hand, and the lateral forearm. Motor to all the muscles of the anterior compartment of the arm, the pectoralis muscles, most forearm flexors, and thenar muscles. Motor to all the muscles of the posterior compartment of the arm and forearm. Motor innervation of the latissimus dorsi.

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Origin

The middle trunk of the brachial plexus originates as the continuation of the seventh cervical root of the brachial plexus.

Course

The middle trunk of the brachial plexus originates in the neck, lateral to the seventh cervical vertebrae, roughly where the plexus reaches the scalene muscles. It runs laterally passing between the anterior and middle scalene muscles and into the posterior triangle of the neck. The middle trunk continues posterior and inferior to the inferior belly of the omohyoid muscle. The middle trunk ends roughly at the midclavicular line, posterior to the clavicle where it splits into divisions.

Branches

The middle trunk of the brachial plexus does not give rise to any nerves and terminates when it splits into the anterior and posterior divisions of the middle trunk. These contribute to the lateral and posterior cords and the nerves that arise from them.

Supplied Structures

The middle trunk supplies both sensory and motor innervation. Targets are indirect as the fibers of the middle trunk first pass through anterior and posterior divisions, then into lateral and posterior cords, respectively, before traveling out through nerves and terminal branches to their target tissues.

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Brachial Plexus

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Destruction of the brachial plexus is indicated for the palliation of cancer pain, including invasive tumors of the distal brachial plexus and tumors of the soft tissue and bone of the upper extremity.

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