2. LEARNING OBJECTIVES
• Mention formation of brachial plexus
(roots, trunk, division, and cords)
• Discuss the relation of brachial plexus
also in connection to clavicle (Supra,
retro, infra clavicular parts
• Enumerate the branches arising the
different cords
3. Brachial plexus
• The brachial plexus is a network of nerve
formed by cervical and thoracic spinal nerves fibres
that supplies the skin and musculature of the upper
limb.
• It begins in the root of the neck, passes through
the axilla, and enters the upper arm.
• The brachial plexus is divided by the clavicle into:
– Supraclavicular
– Retroclavicular
– Infraclavicular parts.
6. Supra
Clavicular
Roots
Found to emerge between the scalenus anterior
and scalenus medius muscles.
Trunks
Traverses the lower part of the posterior
triangle of the neck
Retro
Clavicular
Divisions Lies behind the 1/3 rd of clavicle.
Infra
Clavicular
Cords
The cords of the brachial plexus derived their
names based on their relationship with the 2nd
part of the axillary artery
7. Brachial plexus
• The plexus is formed by the anterior primary
rami (divisions) of the cervical spinal nerves
C5, C6, C7 and C8, and the first thoracic spinal
nerve, T1.
• In addition two communicating twigs usually
join the plexus:
• a) A twig from C4 descends to C5
• b) A twig from T2 ascends to T1.
9. Brachial plexus
• In the axilla and the proximal aspect
of the upper limb, the three cords
give rise to five major branches.
• These nerves continue into the upper
limb to provide innervation to the
muscles and skin present.
10. Prefixed & postfixed brachial plexus
• When branch of C4 is large, branch from T1 is
reduced (from T2 absent), the brachial plexus is
called prefixed.
– i.e. The superiormost root (anterior ramus) of the
plexus is C4 and the inferiormost root is C8, it is a
prefixed brachial plexus.
• When branch of C4 is smaller(or absent), branch
from T2 is lager. The brachial plexus is called
postfixed.i.e.
– When the superior root is C5/C6 and the inferior root is
T2, it is a postfixed brachial plexus.
11. Brachial plexus
• The brachial plexus is divided into five parts.
• The roots and trunks are
located in the neck,
divisions behind the
clavicle and the cords
in the axilla.
Roots Trunks Divisions Cords branches
15. RELATIONS OF THE BRACHIAL PLEXUS
• Brachial plexus lies at the posterior triangle of the
neck between the angle formed by the clavicle and
the stenocleidomastoid muscle.
• Found to emerge between the scalenus anterior
and scalenus medius muscles.
• It is covered by the skin, deep fascia, and platysma
muscle
– It is also crossed by suprascapular nerve, external jugular
vein, and inferior belly of Omohyoid muscle
17. Roots
• The ‘roots’ refer the beginning of the brachial
plexus. They are formed by the spinal nerves C5, C6,
C7, C8 and T1.
• At each vertebral level, paired spinal nerves arise. They
leave the spinal cord via the intervertebral foramina of
the vertebral column.
• Each spinal nerve then divides into anterior and
posterior nerve fibres. The roots of the brachial plexus
are formed by the anterior primary divisions of spinal
nerves C5-T1
– The posterior divisions go on to innervate the skin and
musculature of the trunk.
• Close to their origin, the roots receive gray rami communicantes
from the sympathetic trunk.
19. Trunks
• At the base of the neck, the roots of the brachial
plexus converge, forming three trunks.
Superior
trunk
A combination of C5 and C6
roots
Middle
trunk
A continuation of C7
Inferior
trunk
A combination of C8 and T1
roots
20. Trunks
• The trunks begin to move laterally, crossing
the posterior triangle of the neck.
• The roots and trunks enter the posterior triangle of
the neck by passing between the anterior scalene
and middle scalene muscles and lie superior and
posterior to the subclavian artery.
• The inferior trunk lies on rib I posterior to the
subclavian artery; the middle and superior trunks
are more superior in position.
21. Divisions
• Within the posterior triangle of the neck, each trunk
divides into two branches.
• One division travels anteriorly (toward the front of the
body) and the other posteriorly (towards the back of
the body). Thus, they are known as the anterior and
posterior divisions.
• There are three anterior and three posterior nerve
fibres. These divisions leave the posterior triangle and
pass into the axilla region. They recombine in the next
part of the brachial plexus.
– No peripheral nerves originate directly from the divisions of
the brachial plexus.
22. Cords
• Once the anterior and posterior divisions
have entered the axilla, they combine
together to form three nerves.
• These nerves are named by their position
relative to the axillary artery.
23. Cords
– .
The lateral cord
is formed by
The anterior division of the superior
trunk
The anterior division of the middle
trunk
The posterior cord
is formed by
The posterior division of the superior
trunk
The posterior division of the middle
trunk
The posterior division of the inferior
trunk
The medial cord
is formed by
The anterior division of the inferior
trunk
24. Cords
• The cords give rise to the major branches of the
brachial plexus.
• Most of the major peripheral nerves of the upper
limb originate from the cords of the brachial plexus.
• Generally, nerves associated with the anterior
compartments of the upper limb arise from the
medial and lateral cords and nerves associated with
the posterior compartments originate from the
posterior cord.
25. Branches from the roots & trunk
From roots
(3 nerves)
Dorsal scapular nerve to rhomboids
& leavator scapulae
Long thoracic nerve to serratus ant.
Nerve to subclavius
From upper trunk
(one nerve)
Suprascapular nerve to supraspinatus &
infraspinatus
*NO BRANCH ARISES FROM THE MIDDLE OR FROM THE LOWER TRUNK
30. Branches of the Lateral Cord
• Three nerves originate entirely or partly from the
lateral cord.
1. The lateral pectoral nerve (C5,6,7)
2. The musculocutaneous
nerve(C5,6,7)
3. The lateral root of the median nerve
(C5,6,7)
31. Branches of the Lateral Cord
1. The lateral pectoral nerve is the most
proximal of the branches from the lateral
cord.
• It passes anteriorly, together with the
thoraco-acromial artery, to penetrate the
clavipectoral fascia that spans the gap
between the subclavius and pectoralis minor
muscles, and innervates the pectoralis major
muscle.
32. Branches of the Lateral Cord
2. The lateral root of the median nerve is
the largest terminal branch of the
lateral cord and passes medially to join
a similar branch from the medial cord
to form the median nerve.
33. Branches of the Lateral Cord
3. The musculocutaneous
nerve is a large terminal branch
of the lateral cord, terminating as
the lateral cutaneous nerve of
the forearm.
34. Branches of the Medial Cord
• The medial cord has five branches.
1. The medial pectoral nerve (C8,T1)
2. The medial cutaneous nerve of the arm (medial
brachial cutaneous nerve) (T1,2)
3. The medial cutaneous nerve of the forearm
(medial antebrachial cutaneous nerve) (C8,T1)
4. The medial root of the median nerve (C8,T1)
5. The ulnar nerve (C7,8,T1)
35. Branches of the Medial Cord
1. The medial pectoral nerve is the most proximal
branch.
• It receives a communicating branch from the
lateral pectoral nerve and then passes anteriorly
between the axillary artery and axillary vein.
• Branches of the nerve penetrate and supply the
pectoralis minor muscle. Some of these branches
pass through the muscle to reach and supply the
pectoralis major muscle.
• Other branches occasionally pass around the
inferior or lateral margin of the pectoralis minor
muscle to reach the pectoralis major muscle.
36. Branches of the Medial Cord
2. The medial cutaneous nerve of the arm (medial
brachial cutaneous nerve) passes through the
axilla and into the arm where it penetrates deep
fascia and supplies skin over the medial side of the
distal third of the arm. In the axilla, the nerve
communicates with the intercostobrachial
nerve of T2.
• Fibers of the medial cutaneous nerve of the arm
innervate the upper part of the medial surface of
the arm and floor of the axilla.
37. Branches of the Medial Cord
3. The medial cutaneous nerve of the forearm
(medial antebrachial cutaneous nerve) originates
just distal to the origin of the medial cutaneous
nerve of the arm.
• It passes out of the axilla and into the arm where it
gives off a branch to the skin over the biceps
brachii muscle, and then continues down the arm
to penetrate the deep fascia with the basilic vein,
continuing interiorly to supply the skin over the
anterior surface of the forearm.
• It innervates skin over the medial surface of the
forearm down to the wrist.
38. Branches of the Medial Cord
4. The medial root of the median
nerve passes laterally to join with a
similar root from the lateral cord to
form the median nerve anterior to the
third part of the axillary artery.
5. The ulnar nerve.
39. Branches of the Posterior Cord
• Five nerves originate from the posterior
cord of the brachial plexus:
1. The superior subscapular nerve (C5,6)
2. The thoracodorsal nerve to Latissmus dorsi
(C6,7,8)
3. The inferior subscapular nerve (C5,6)
4. The axillary nerve (C5,6)
5. The radial nerve(c5,6,7,8,T1)
40. Branches of the Posterior Cord
1. The superior subscapular nerve is short and
passes into and supplies the subscapularis
muscle.
2. The inferior subscapular nerve also passes
inferiorly along the posterior axillary wall and
innervates the subscapularis and teres major
muscles
41. Branches of the Posterior Cord
3. The thoracodorsal nerve is the longest
of these three nerves and passes
vertically along the posterior axillary
wall.
• It penetrates and innervates the
latissimus dorsi muscle.
42. Branches of the Posterior Cord
4. The axillary nerve originates from the
posterior cord and passes inferiorly and
laterally along the posterior wall to exit the
axilla through the quadrangular space. It
passes posteriorly around the surgical neck
of the humerus and innervates both
the deltoid and teres minor muscles.
5. The radial nerve.
44. Major Branches
• In the axilla and the proximal aspect of the upper
limb, the three cords give rise to five major
branches. These nerves continue into the upper
limb to provide innervation to the muscles and skin.
– 1) MEDIAN
– 2) ULNAR NERVE
– 3) MUSCULOCUTANEOUS NERVE
– 4) AXILLARY NERVE
– 5) RADIAL NERVE
45. Musculocutaneous Nerve
• Roots: C5, C6, C7.
• Motor Functions: Innervates the
brachialis, biceps brachii and
coracobrachialis muscles.
• Sensory Functions: Gives off the lateral
cutaneous branch of the forearm, which
innervates the lateral half of the anterior
forearm, and a small lateral portion of
the posterior forearm.
46. Axillary Nerve
• Roots: C5 and C6.
• Motor Functions: Innervates the
teres minor and deltoid muscles.
• Sensory Functions: Gives off the
superior lateral cutaneous nerve of
arm, which innervates the inferior
region of the deltoid (“regimental
badge area”).
47. Median Nerve
• Roots: C6 – T1. (Also contains fibres from C5 in
some individuals).
• Motor Functions: Innervates most of the flexor
muscles in the forearm, the thenar muscles, and the
two lateral lumbricals that move the index and
middle fingers.
• Sensory Functions: Gives off the palmar cutaneous
branch, which innervates the lateral part of the
palm, and the digital cutaneous branch, which
innervates the lateral three and a half fingers on the
anterior (palmar) surface of the hand.
48. Radial Nerve
• Roots: C5-C8 and T1.
• Motor Functions: Innervates the triceps
brachii, and the extensor muscles in the
posterior compartment of the forearm.
• Sensory Functions: Innervates the
posterior aspect of the arm and forearm,
and the posterior, lateral aspect of the
hand.
49. Ulnar Nerve
• Roots: C8 and T1.
• Motor Functions: Innervates the muscles of
the hand (apart from the thenar muscles and
two lateral lumbricals), flexor carpi ulnaris and
medial half of flexor digitorum profundus.
• Sensory Functions: Innervates the anterior
and posterior surfaces of the medial one and
half fingers, and associated palm area.
51. "Erb's point"
.
• A Erb’s point : Is the region on upper trunk
of brachial plexus where :
• It is formed by union two roots – Ventral rami
of C5&C6
• It divides into two divisions
– anterior and posterior divisions
• It provides origin to two nerves
– suprascapular and nerve to subclavius
54. Clinical Relevance
• Injury to the Brachial Plexus
• An intact brachial plexus is vital for the
normal function of the upper limb.
• There are two major types of injuries that
can affect the brachial plexus.
• An upper brachial plexus injury affects the
superior roots, and a lower brachial plexus
injury affects the inferior roots.
55. Lower Brachial Plexus Injury
Klumpke Palsy
• A lower brachial plexus injury results from excessive
abduction of the arm (e.g person catching a branch as they
fall from a tree). It has a much lower incidence than Erb’s
palsy.
• Nerves affected: Nerves derived from the T1 root – ulna and
median nerves.
• Muscles paralysed: All the small muscles of the hand (the
flexors muscles in the forearm are supplied by the ulna and
median nerves, but are innervated by different roots).
• Sensory functions: Loss of sensation along medial side of
arm.
• The metacarpophalangeal joints are hyperextended, and the
interphalangeal joints are flexed. This gives the hand a clawed
appearance.
57. Upper Brachial Plexus Injury
Erb’s Palsy
• Erb’s palsy commonly occurs where there is excessive increase in the angle
between the neck and shoulder – this stretches (or can even tear) the nerve
roots, causing damage. It can occur as a result of result of a difficult birth or
shoulder trauma.
• Nerves affected: Nerves derived from solely C5 or C6 roots;
musculocutaneous, axillary, suprascapular and nerve to subclavius.
• Muscles paralysed: Supraspinatus, infraspinatus, subclavius, biceps brachii,
brachialis, coracobrachialis, deltoid and teres minor.
• Motor functions: The following movements are lost or greatly weakened –
abduction at shoulder, lateral rotation of arm, supination of forearm, and
flexion at shoulder.
• Sensory functions: Loss of sensation down lateral side of arm, which covers
the sensory innervation of the axillary and musculocutaneous nerves.
• The affected limb hangs limply, medially rotated by the unopposed action of
pectoralis major. The forearm is pronated due to the loss of biceps brachii.
This is position is known as ‘waiter’s tip’, and is characteristic of Erb’s palsy.
58. Erb's palsy: upper brachial plexus injury
• Arm cannot be raised, since deltoid (axillary nerve ) &
spinati muscles (suprascapular nerve) are paralyzed
• Elbow flexion is weakened because of weakness in
biceps & brachialis;
• Weakness in retraction and protraction of scapula -
due to paralysis of rhomboids and serratus anterior, if
roots are damaged above their junction
• Lateral arm loses sensation
• "Waiter's Tip" position, where the limb hangs limp in a
medially rotated position
• Usually caused by an increased angle between neck
and shoulder, eg. falling on your head.
59. Compression of the cords
• Pain radiating dfown the arm
• Hand numbness
• Hand weakness
• Caused by prolonged hyperabduction,
eg. painting the ceiling; cords get
pinched between coracoid process and
pectoralis minor tendon.
60. Klumpke paralysis: lower brachial plexus injury
• Weakness in intrinsics of hand as well as long
flexors & extensors of the fingers, and you get a
"claw hand"
• A sensory deficit ialong the medial aspect of the
arm, forearm, hand
• Associated Horner's syndrome
– Caused when the arm is suddenly pulled superiorly, eg.
when you grab something while falling vertically down.