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What are the Nerves from the Neck to the Arm?

Published in Nervous System 3 mins read

The nerves from the neck to the arm are collectively known as the brachial plexus.

The brachial plexus is a complex network of nerves that originates from nerve roots in the cervical (neck) and upper thoracic (chest) regions of the spinal cord. Specifically, it's formed by the ventral rami of spinal nerves C5, C6, C7, C8, and T1 (and sometimes contributions from C4 and T2). This intricate system provides both motor and sensory innervation to the entire upper limb, including the shoulder, arm, forearm, and hand.

Formation and Branches of the Brachial Plexus

The brachial plexus is commonly described in terms of its roots, trunks, divisions, cords, and branches (often remembered with the mnemonic "Randy Travis Drinks Cold Beer").

  • Roots: The ventral rami of the spinal nerves C5, C6, C7, C8, and T1.

  • Trunks: These roots merge to form three trunks:

    • Superior trunk: Formed by the union of C5 and C6 roots.
    • Middle trunk: Continuation of the C7 root.
    • Inferior trunk: Formed by the union of C8 and T1 roots.
  • Divisions: Each trunk then divides into an anterior and posterior division.

  • Cords: The divisions recombine to form three cords, named based on their relationship to the axillary artery:

    • Lateral cord: Formed by the anterior divisions of the superior and middle trunks.
    • Posterior cord: Formed by the posterior divisions of all three trunks.
    • Medial cord: Formed by the anterior division of the inferior trunk.
  • Branches: The cords give rise to several major peripheral nerves that innervate the upper limb:

    • Musculocutaneous nerve: Arises from the lateral cord. It innervates the biceps brachii, brachialis, and coracobrachialis muscles, and provides sensory innervation to the lateral forearm.
    • Axillary nerve: Arises from the posterior cord. It innervates the deltoid and teres minor muscles, and provides sensory innervation to the shoulder region.
    • Radial nerve: Also arises from the posterior cord. It is the largest branch of the brachial plexus and innervates the triceps brachii, brachioradialis, and extensor muscles of the forearm and hand. It also provides sensory innervation to the posterior arm, forearm, and dorsal aspect of the hand.
    • Median nerve: Formed by branches from both the lateral and medial cords. It innervates most of the flexor muscles of the forearm and some of the intrinsic muscles of the hand. It also provides sensory innervation to the palmar aspect of the thumb, index finger, middle finger, and lateral half of the ring finger.
    • Ulnar nerve: Arises from the medial cord. It innervates some of the flexor muscles of the forearm and most of the intrinsic muscles of the hand. It also provides sensory innervation to the medial side of the hand, including the little finger and the medial half of the ring finger.

Clinical Significance

Damage to the brachial plexus can result in a variety of conditions, including:

  • Brachial plexus injuries: These can occur from trauma, such as car accidents or sports injuries.
  • Thoracic outlet syndrome: Compression of the brachial plexus and subclavian vessels in the space between the clavicle and first rib.
  • Neuropathies: Damage to specific nerves of the brachial plexus, such as carpal tunnel syndrome (median nerve) or cubital tunnel syndrome (ulnar nerve).

Understanding the anatomy and function of the brachial plexus is crucial for diagnosing and treating conditions affecting the upper limb.