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ates as cutaneous branches supplying the skin of the back of the
The brachial plexus (C5,6,7,8,T1) (Fig. 30.1)
wrist and hand.
• The plexus arises as five roots. These are the anterior primary rami of
C5,6,7,8,T1. The roots lie between scalenus anterior and scalenus
damage to the radial nerve in the spiral groove.
medius. • Effect of injury (Fig. 31.2): e.g. humeral shaft fracture resulting in
• The three trunks (upper, middle and lower) lie in the posterior tri- • Motor deficitaloss of all forearm extensors: wristdrop.
angle of the neck. They pass over the 1st rib to lie behind the clavicle. • Sensory deficitausually small due to overlap: sensory loss over the
• The divisions form behind the middle third of the clavicle around the anatomical snuffbox is usually constant.
axillary artery.
• The cords lie in the axilla and are related medially, laterally and pos- The musculocutaneous nerve (C5,6,7)
teriorly to the second part of the axillary artery. • Type: mixed sensory and motor.
• Terminal nerves arise from the cords surrounding the third part of the • Origin: it arises from the lateral cord of the brachial plexus.
axillary artery. • Course: it passes laterally through the two conjoined heads of cora-
cobrachialis and then descends the arm between brachialis and biceps,
The axillary nerve (C5,6) supplying all three of these muscles en route. It pierces the deep fascia
• Type: mixed sensory and motor nerve. just below the elbow (and becomes the lateral cutaneous nerve of the
• Origin: it arises from the posterior cord of the brachial plexus. forearm). Here it supplies the skin of the lateral forearm as far as the
• Course: it passes through the quadrangular space with the posterior wrist.
circumflex humeral artery. It provides: a motor supply to deltoid and
teres minor; a sensory supply to the skin overlying deltoid; and an articu- The median nerve (C6,7,8,T1) (Fig. 30.3)
lar branch to the shoulder joint. • Type: mixed sensory and motor.
• Effect of injury: the axillary nerve is particularly prone to injury • Origin: it arises from the confluence of two roots from the medial
from the downward displacement of the humeral head during shoulder and lateral cords lateral to the axillary artery in the axilla.
dislocations. • Course and branches: the median nerve initially lies lateral to the
• Motor deficitaloss of deltoid abduction with rapid wasting of this brachial artery but crosses it medially in the mid-arm. In the cubital
muscle. Loss of teres minor function is not detectable clinically. fossa it lies medial to the brachial artery which lies medial to the bicipi-
• Sensory deficitais limited to the ‘badge’ region overlying the tal tendon. The median nerve passes deep to the bicipital aponeurosis
lower half of deltoid. then between the two heads of pronator teres. A short distance below
this the anterior interosseous branch is given off. This branch descends
The radial nerve (C5,6,7,8,T1) (Fig. 30.2) with the anterior interosseous artery to supply the deep muscles of the
• Type: mixed sensory and motor. flexor compartment of the forearm except for the ulnar half of flexor
• Origin: it arises as a continuation of the posterior cord of the brachial digitorum profundus. In the forearm the median nerve lies between
plexus. flexor digitorum superficialis and flexor digitorum profundus and
• Course and branches: it runs with the profunda brachii artery supplies the remaining flexors except for flexor carpi ulnaris. A short
between the long and medial heads of triceps into the posterior com- distance above the wrist it emerges from the lateral side of flexor
partment and down between the medial and lateral heads of triceps. digitorum superficialis and gives off the palmar cutaneous branch
At the midpoint of the arm it enters the anterior compartment by piercing which provides a sensory supply to the skin overlying the thenar
the lateral intermuscular septum. In the region of the lateral epicondyle eminence.
the radial nerve lies under the cover of brachioradialis and divides At the wrist the median nerve passes beneath the flexor retinaculum
into the superficial radial and posterior interosseous nerves. (i.e. through the carpal tunnel) in the midline and divides here into its
The branches of the radial nerve include: branches to triceps, bra- terminal branches: the recurrent branch to the muscles of the thenar
chioradialis and brachialis as well as some cutaneous branches. It ter- eminence (but not adductor pollicis); the branches to the 1st and 2nd
minates by dividing into two major nerves: lumbricals; and the cutaneous supply to the palmar skin of the thumb,
• The posterior interosseous nerveapasses between the two heads index, middle and lateral half of the ring fingers.
of supinator at a point three fingerbreadths distal to the radial • Effect of injury (see Fig. 31.2): e.g. compression as in carpal tunnel
head thus passing into the posterior compartment. It supplies the syndrome.
extensor muscles of the forearm. • Motor deficitaweakness and wasting of the thenar muscles.
• The superficial radial nerveadescends the forearm under the cover • Sensory deficitainvolves the skin over the lateral palm and lateral
of brachioradialis with the radial artery on its medial side. It termin- three digits. This is highly variable due to overlap.

Nerves of the upper limb I 71