UPPER LIMB
OSCE
Station 2
Brachial Plexus
What is the origin of the brachial plexus?
"The brachial plexus is formed from the ventral rami of the lower four cervical and first thoracic nerve roots (C5-C8, T1).
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Label the parts on the image.
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Describe the surgical approach to the supraclavicular and infraclavicular branches of the brachial plexus?
The supraclavicular branches of the brachial plexus are approachable through the neck. The infraclavicular branches can be approached through the axilla.
Name the branches which arise from the lateral cord and the muscles they innervate.
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The lateral cord has three branches:
- Lateral pectoral nerve : Innervates pectoralis major (along with the medial pectoral nerve).
- Lateral root of the median nerve : Innervates forearm flexors (except ulnar half of FDP) and ‘LOAF muscles in the hand [Lateral (radial) two lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis].
- Musculocutaneous nerve : Innervates biceps brachii, brachialis and coracobrachialis. It continues as the lateral cutaneous nerve of the forearm.
Name the branches which arise from the medial cord and the muscles they innervate.
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- Medial pectoral nerve : Innervates pectoralis minor and part of pectoralis major.
- Medial cutaneous nerve of the arm : Cutaneous innervation of skin on medial side of arm.
- Medial cutaneous nerve of the forearm: Cutaneous innervation of skin on medial side of forearm.
- Medial root of the : Joins the lateral root of the median nerve median nerve to supply the muscles listed above.
- Ulnar nerve : Innervates FCU, ulnar half of FDP, intrinsic muscles in hand except ‘LOAF.’
Name the branches which arise from the posterior cord and the muscles they innervate.
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- Upper subscapular nerve : Innervates subscapularis.
- Lower scapular nerve : Innervates subscapularis and teres major
- Nerve to latissimus dorsi (thoracodorsal nerve) : Innervates latissimus dorsi.
- Axillary nerve : Innervates deltoid (anterior branch), teres minor (posterior branch) and the long head of triceps in some individuals.
- Radial nerve : Innervates triceps and all extensors of the forearm, wrist and digits.
Name the five terminal branches of the brachial plexus.
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The terminal branches of the brachial plexus are the:
- Musculocutaneous nerve.
- Axillary nerve.
- Radial nerve.
- Median nerve.
- Ulnar nerve.
How does injury to the axillary nerve clinically present?
"Injury to the axillary nerve is indicated by paralysis of the deltoid and loss of sensation over a small area of skin covering the central part of the deltoid known as the ‘regimental badge area’ (upper lateral cutaneous nerve of the arm arising from the posterior division of the axillary nerve) corresponding to the C5 dermatome.
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Name the root values of the reflexes commonly tested in the upper limb.
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- Biceps C5/C6 : Musculocutaneous nerve.
- Supinator C6/C7 : Radial nerve.
- Triceps C7/C8 : Radial nerve.
What are the common obstetric brachial plexus injuries.
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- Injury to the upper trunk of the brachial plexus (C5/C6) results in an adducted and internally rotated arm with an extended elbow and pronated forearm (Erb-Duchenne’s palsy) usually due to shoulder dystocia during birth. The most commonly affected nerves are the suprascapular, musculocutaneous and axillary nerves.
- Injury to the lower trunk of the brachial plexus (C8-T1) results in wasting of the intrinsic muscles of the hand (Klumke’s palsy). This is usually due to traction on an abducted arm during childbirth. The classic presentation is of a clawed hand. Involvement of T1 may result in Horner’s syndrome.