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  • 22 January, 2021

UPPER LIMB

BRACHIAL PLEXUS

  • The brachial plexus is a network of nerves that provides movement and feeling to the shoulder, arm
    and hand.
  • The nerves supporting the arm exits the spinal column high in the neck and the nerves that support the hand and fingers exit lower in the neck.
  • This nerve complex comprises four cervical nerve roots (C5-C8) and the first thoracic nerve root (T1). These roots combine to form three trunks. Each nerve root is derived from the corresponding ventral or primary rami of the spinal nerve. C5-C6 form the upper trunk, C7 continues as the middle trunk and C8-T1 form the lower trunk.
  • Each trunk splits and forms a division. Half of them supply flexor muscles (that lift and bend the arm) and the rest supply the extensor muscles (that straighten the arm and bring it down).
  • The anterior divisions of the upper and middle trunk unite to form the lateral cord;
  • The anterior division of the lower trunk continues as the medial cord and all 3 posterior divisions unite forming the posterior cord. The nerve cords derive their names with respect to their relationship with the axillary artery.
  • The lateral cord lies on the lateral (or outer) side of the axillary artery; the medial cord lies on the medial (or inner) side of the axillary artery and the posterior cord lies behind the axillary artery.
  • The cords then branch out forming different nerves that supply all of the muscles of the upper extremity.

BRANCHES OF BRACHIAL PLEXUS

  • Branches of the Roots:
    • Nerve to serratus Anterior (Long Thoracic N of Bell),(C5,C6,C7)
    • Nerve to rhomboideus (Dorsal scapular.N),(C5)
  • Branches of the Trunks:
    • N (C5,C6)
    • Nerve to Subclavius (C5,C6)
  • Branches of the cords:
    • Branches of Lateral cord (LML)
      • Lateral Pectoral. N(C5 – C7)
      • Musculo – Cutaneous. N (C5 – C7)
      • Lateral root of Median. N (C5 – C7)
  • Branches of Medial cord (M4U)
    • Medial Pectoral.N (C8,T1)
    • Medial Cutaneous. N of arm (C8,T1)
    • Medial Cutaneous. N of fore – arm (C8,T1)
    • Medial root of median. N (C8,T1)
    • Ulnar.N (C7,C8,T1)
  • Branches of Posterior cord (ULNAR)
    • Upper Subscapular (C5,C6)
    • Lower Subscapular (C5,C6)
    • Nerve to Latissmus dorsi (thoraco-dorsal)(C6,C7,C8)
    • Axillary.N (C5,C6)
CLINICAL POINTS
  1. In some brachial plexus injuries sympathetic nerve fibers that traverse T1 can be damaged. The condition known as Horner’s syndrome is caused by damage to the sympathetic nervous system and is often associated with injuries to the brachial plexus network of nerves including Erbs palsy which frequently occurs as a birth injury caused by the use of excessive force during delivery most often by inappropriate traction being applied to the head which damages nerves in the area of the shoulder and neck. Symptoms of Horners syndrome include a drooping upper eyelid, elevation of the lower lid, a constricted pupil, delay in dilation of the pupil, an appearance of a slightly sunken eye and a decrease in sweating on the side of the face affected by the condition with occasional differences in eye colour.
  2. The condition in adults known as ‘wry neck’ may be described as a temporary form of torticollis (Twisted Neck). Wry neck is often caused by sleeping in an awkward position as a result of which the neck feels painful and stiff since the muscles are in spasm and the head may be held at an angle until spontaneous recovery occurs over a period of a few hours or a few days. The symptoms of torticollis are somewhat similar and this condition can be a birth injury caused by damage to the muscles of the neck during a vigorous and physical birth. Torticollis is usually noticed between 6 months and 3 years of age due to head tilt over one side.