From doctor muwanga makerere university Uganda

1. THE BRACHIAL PLEXUS
BY GM MUWANGA

2. Brachial plexus
• a network of nerve fibres that supplies the
skin & musculature of the:
 upper limb
 parts of the shoulder & pectoral regions

3. Brachial plexus (contn.)
• originates in the root of the neck
• passes through the interscalene space
• passes through costoclavicular corridor

4. Course of brachial plexus through interscalene space & costoclavicular
corridor

5. Brachial plexus (contn.)
• continues into axillary cavity to reach
the root of the upper extremity
• in the axilla its terminal branches are
constituted

6. Brachial plexus (contn.)
• for much of its course, the plexus is
accompanied by the:
 axillary artery
 subclavian
 axillary vein

7. Brachial plexus (contn.)
• common arrangement is such that the
plexus is formed by the anterior (ventral)
rami (branches) of:
 last four cervical spinal nerves
 first thoracic spinal nerve

8. Brachial plexus (contn.)
• hence the contributing nerves are:
 cervical spinal nerves C5, C6, C7 & C8
 first thoracic spinal nerve, T1

9. The spinal cord outflow at
each vertebral level. The
anterior rami of vertebral
levels C5-C8 and T1 make
up the roots of the
brachial plexus

10. Brachial plexus (contn.)
• however, the origin of the plexus may
shift by:
 one spinal cord segment upwards
or
 one spinal cord segment downwards

11. Brachial plexus (contn.)
• this results in either:
 a pre-fixed brachial plexus
or
 a post-fixed brachial plexus

12. Brachial plexus (contn.)
• in a pre-fixed plexus,:
 contribution by C4 is large
 contribution from T1 is absent
 hence C4 – C8 constitute plexus

13. Brachial plexus (contn.)
• in a post-fixed plexus, there is:
 contribution by T2
 C5 contribution is absent
 hence C6 – T2 constitute plexus

14. Brachial plexus (contn.)
• consists of four components:
 roots
 trunks
 divisions

15. Brachial plexus (contn.)
• following mnemonic can help you
remember the components:
 Read That Damn Cadaver Book

16. Components of
the brachial plexus

17. Brachial plexus (contn.)
• roots & trunks are located in the neck
• divisions located posterior to the clavicle
• cords located in the axilla

18. Roots
• refer to the origin of the brachial plexus
from the spinal cord
• roots involved belong to spinal nerves
C5, C6, C7, C8 & T1

20. Roots (contn.)
• at each vertebral level, paired spinal
nerves arise, one on either side of the body
• they leave the spinal cord via the
intervertebal foramina of the vertebral
column

21. Spinal nerve, spinal nerve branches (rami) & spinal nerve
roots

23. Roots (contn.)
• each nerve then divides into anterior &
posterior ramus (ramus = branch)
• roots of the brachial plexus are formed by the
anterior (ventral) rami of spinal nerves C5-T1

24. Roots (contn.)
• anterior rami pass between the anterior &
middle scalene (interscalene space)
• posterior (dorsal) rami go on to innervate
the skin & musculature close to the
vertebral column

25. Deep dissection of the neck – anterior view: note brachial plexus – the
roots are located between anterior & middle scalene muscles

26. Trunks
• union of the anterior rami of spinal nerves
C5, C6, C7, C8 & T1 forms three trunks
• structures are named according to their
anatomical position
• trunks lie lateral to the interscalene
space superior to the clavicle

27. Trunks (contn.)
• hence the following trunks are formed:
 upper (superior) trunk
 middle trunk
 lower (inferior) trunk

28. Trunks (contn.)
• upper trunk formed by union of C5 & C6
anterior rami
• middle trunk is isolated continuation
of C7 anterior ramus
• lower trunk formed by union of C8 &
T1 anterior rami

29. Formation of trunks

31. Deep
dissection
of the
neck –
note
formation
of trunks
of the
brachial
plexus

32. Divisions
• each trunk divides into two branches
known as the anterior & posterior
divisions
• divisions lie posterior to the clavicle

33. Deep dissection of neck – note formation of divisions of brachial plexus

34. 1
2
3
4
5
6
7
8 9
Deep dissection of
the neck – note
formation of the
divisions of the
brachial plexus:
1. Upper trunk
2. Anterior division
3. Posterior
division
4. Middle trunk
5. Anterior division
6. Posterior
division
7. Posterior
division
8. Anterior division
9. Lower trunk

35. Divisions (contn.)
• there are now three anterior & three
posterior divisions
• these divisions pass into the axilla

36. Divisions (contn.)
• anterior divisions contain neurons
which are destined to flexor muscles
• posterior division has axons destined
to extensor muscles

37. Brachial plexus – formation of divisions: note that anterior divisions
contain axons for flexor muscles while posterior divisions carry axons
for extensor muscles

38. Cords
• anterior & posterior divisions enter axilla
& combine to form three cords
• latter are named according their position
relative to the axillary artery

39. Cords (contn.)
• cords are:
 lateral cord (lateral to axillary artery)
 medial cord (medial to axillary artery)
 posterior cord (posterior to axillary artery)

40. Relations between the
cords & axillary artery

41. Cords (contn.)
• lateral cord formed by:
 anterior division of the superior trunk
 anterior division of the middle trunk

42. Cords (contn.)
• posterior cord formed by:
 posterior division of the superior trunk
 posterior division of the middle trunk
 posterior division of the inferior trunk

43. Cords (contn.)
• medial cord is formed by:
 anterior division of the inferior trunk
only

44. Brachial plexus –
formation of cords

45. Terminal branches
• the three cords give rise to five terminal
branches in the axilla
• terminal branches continue into the upper
limb to provide motor & sensory
innervation

46. Brachial plexus –
terminal branches

47. Terminal branches (contn.)
• terminal branches are:
 musculocutaneous nerve
 axillary nerve
 median nerve
 radial nerve
 ulnar nerve

48. Terminal branches (contn.)
• nerves derived from the posterior cord end up
in the posterior compartment of the arm &
forearm
• this is because the posterior cord is
constituted by divisions that contain neurons
for extensor muscles of the upper limb

49. Terminal branches (contn.)
• hence terminal branches for the posterior
(extensor) compartments are:
 the radial nerve
 axillary nerve

50. Terminal branches (contn.)
• nerves derived from lateral & medial cords
innervate muscles located in the anterior
compartment
• this is because these cords are derived from
divisions containing neurons for flexor
muscles of the upper limb

51. Terminal branches (contn.)
• hence the terminal branches for the
anterior (flexor) compartments are:
 musculocutaneous nerve
 median nerve
 ulnar nerve

52. Brachial plexus –
terminal branches

53. Brachial plexus – formation of terminal branches

54. Musculocutaneous nerve
• roots: C5, C6, C7
• motor component – innervates:
 brachialis muscle
 biceps brachii muscle
 corocobrachialis muscle

55. Musculocutaneous nerve (contn.)
• sensory component:
• lateral antebrachial cutaneous n. which innervates:
 the lateral half of the anterior forearm
 a small lateral portion of the posterior
forearm
• articular branches innervate the joint capsule

56. Formation of musculocutaneous nerve

57. Musculocutaneous
nerve: cutaneous
distribution
Posterior view
Anterior view

58. Axillary nerve
• roots: C5 and C6
• motor component – innervates:
 deltoid muscle
 teres minor muscle

59. Axillary nerve (contn.)
• sensory component - gives off:
• superior lateral cutaneous nerve of arm
 it innervates the inferior region of the
deltoid (“regimental badge area”)

60. Formation of axillary nerve

61. Axillary nerve:
cutaneous distribution
- right limb
Posterior view
Anterior view

62. Median nerve
• roots: C6 – C8 and T1
• motor component - innervates:
 most of the flexor muscles in the forearm
 the thenar muscles
 the two lateral lumbrical muscles that
move the index and middle fingers

63. Median nerve (contn.)
• sensory component - gives off the palmar
cutaneous branch:
 innervates the lateral part of the palm

64. Median nerve (contn.)
• sensory component – gives off the digital
cutaneous branch:
 innervates the lateral three-and-half
fingers on the anterior (palmar) surface
of the hand

65. Formation of median nerve

66. Median nerve:
cutaneous
distribution
Posterior view
Anterior
view

67. Radial nerve
• roots: C5-C8 and T1
• motor component - innervates the:
 triceps brachii & anconeus
 extensor muscles in the posterior
compartment of the forearm

68. Radial nerve (contn.)
• sensory component – innervates:
 posterior aspect of the arm & forearm
 posterior, lateral aspect of the hand
(by its superficial branch)

69. Formation of radial nerve

70. Radial nerve:
cutaneous
distribution
Posterior view
Anterior view

71. Ulnar nerve
• roots: C8 and T1
• motor component – innervates:
 muscles of the hand (apart from thenar
muscles & two lateral lumbricals)
 flexor carpi ulnaris
 medial half of flexor digitorum profundus

72. Ulnar nerve (contn.)
• sensory component – innervates:
 anterior & posterior surfaces of the
medial one-and-half fingers
 associated palm area

73. Formation of ulnar nerve

74. Ulnar nerve:
cutaneous
distribution
Posterior view
Anterior view

75. Other branches
• there are other nerves that arise from
all 5 components of the brachial plexus

76. Other branches (contn.)
(I) from roots:
 long thoracic nerve/nerve to serratus
anterior (C5, C6, & C7)
 dorsal scapular n./nerve to rhomboids (C5)
 branches to scalene muscles & longus colli
(C5, C6, C7, and C8)

77. Other branches (contn.)
(II) from trunks:
 suprascapular nerve (C5 and C6)
 nerve to subclavius (C5 and C6)

78. Other branches (contn.)
• from cords:
1. from lateral cord:
 lateral pectoral nerve (C5, C6, and C7)

79. Other branches (contn.)
2. from medial cord:
 medial pectoral nerve (C8 and T1)
 medial cutaneous nerve of arm (T1)
 medial cutaneous nerve of forearm
(C8 and T1)

80. Other branches (contn.)
3. from posterior cord:
 thoraco-dorsal nerve/nerve to latissimus
dorsi (C6, C7, and C8)
 upper subscapular nerve (C5 and C6)
 lower subscapular nerve (C5 and C6)

81. Other branches of
the brachial plexus

82. Some clinical aspects
• there are two major types of injuries that
can affect the brachial plexus
 an upper brachial plexus injury that affects
the superior roots
 a lower brachial plexus injury that affects
the inferior roots

83. Lesions of the brachial plexus
• nerve injuries vary in severity:
 from a mild stretch of nerves
to
 nerve root tearing away from the
spinal cord

84. Lesions of the brachial plexus (contn.)
• injuries include the following:
 avulsion
 rupture
 neuroma

85. Some of the possible brachial
plexus lesions

86. Lesions of the brachial plexus (contn.)
• avulsion:
 nerve is torn away from its attachment
at the spinal cord
 this is the most severe type of injury

87. Lesions of the brachial plexus (contn.)
• rupture:
 nerve is torn, but not at the spinal cord
attachment

88. Lesions of the brachial plexus (contn.)
• neuroma:
• scar tissue grows around the injury site,
resulting in:
 compression of the injured nerve
 nerve failing to send signals to the muscles

89. Lesions of the brachial plexus (contn.)
• neurapraxia:
 nerve has been stretched & damaged
but not torn
 most common type of injury
 such injuries normally heal on their own

90. Conditions involving brachial plexus injuries
• these include:
 Erb’s palsy (Erb–Duchenne palsy)
 Klumpke palsy
 brachial plexus compression syndrome

91. Upper brachial plexus injury – Erb’s palsy
• involves the upper root nerves of C5, C6
• commonly occurs where there is excessive
increase in the angle between the neck
& shoulder
• this stretches (or can even tear) the nerve
roots

92. Erb’s palsy (contn.)
• can occur as a result of:
 a difficult birth (dystochia)
 shoulder trauma in the adult

93. Shoulder dystochia
• occurs when anterior shoulder is obstructed
behind the symphysis pubis
• during manipulation to deliver the fetus, the
the neck & posterior shoulder are stretched
• this may cause injury to the upper brachial
plexus roots

94. Two-dimensional sagittal view of shoulder dystocia during which the
anterior shoulder is impacted behind the pubic symphysis

95. Excessive stretching of the head & neck away from the shoulder during
traction maneuvers

96. Shoulder trauma
• usually follows trauma that causes severe
stretching between the neck & shoulder, e.g.,
 a high fall in which one lands on
the shoulder
 heavy impact during physical sports,
e.g., rugby, American football, etc.

97. Stretching the shoulder
& neck due to a fall from
the height and landing
on the shoulder

98. Erb’s palsy (contn.)
nerves affected:
• only nerves derived from C5 or C6 roots
are affected:
 musculocutaneous
 axillary
 suprascapular
 nerve to subclavius

100. Erb’s palsy (contn.)
• effect on motor functions:
• following movements are lost or greatly
weakened:
 abduction at shoulder
 lateral rotation of arm
 supination of forearm
 flexion at shoulder

101. Erb’s palsy (contn.)
• effect on sensory functions:
 loss of sensation down lateral side of arm
• this is territory covered cutaneous
branches of the axillary & musculo-
cutaneous nerves

102. Erb’s palsy (contn.)
• affected limb hangs limply
• medially rotated by the unapposed
action of pectoralis major

103. Erb’s palsy (contn.)
• forearm is pronated due to the loss of
biceps brachii
• position is known as ‘waiter’s tip’, & is
characteristic of Erb’s palsy

105. The waiters’ tip position, characteristic of
Erb’s palsy. Coloured part represents skin
area that has lost sensation

106. Lower brachial plexus injury – Klumpke palsy
• involves lower root nerves derived
from C8, T1
• lower brachial plexus injury results from
excessive abduction of the arm
• has a much lower incidence than Erb’s palsy

107. Klumpke palsy (contn.)
• excessive abduction of the arm may occur
following, for example:
 traction on an abducted arm as in
dystochia
 person catching a branch as they fall from
a tree

108. Klumpke palsy (contn.)
• traction on an abducted arm may occur as
the infant is being pulled from the birth
canal
• in such a situation, the arm is stretched
& extended arm above the head

109. Traction of the fetus with an extended arm above the head – leading
to an excessive increase in the angle between the trunk and the right
upper limb

110. Klumpke palsy (contn.)
• in the adult, such an increase in the angle
may occur as one catches a branch while
falling from a tree

112. Klumpke palsy (contn.)
• effect on motor functions:
 loss of adduction of the thumb
(ulnar nerve)
 loss of abduction & adduction of
metacarpophalangeal joints
(deep branch of ulnar n. & median n.)

113. Effect on motor functions (contn.):
• loss of flexion at the metatarsophalangeal
joint (deep branch of ulnar n. & median n.)
• loss of extension of the interphalangeal joints
(deep branch of ulnar n. & median n.)

114. Effect on motor functions (contn.):
• weak flexion of proximal interphalangeal
joints & distal interphalangeal joints
(ulnar & median nerve)

115. Effect on motor functions (contn.):
• overall effect resulting from the above
motor deficits leads to a ‘claw hand’
• there is paralysis of the flexors of the
wrist & fingers (C6, C7 & C8), & all
intrinsic muscles of the hand (C8 & T1)

117. A claw hand results
as one attempts to
assume “fist”
position (lightly
shaded)

119. Effect on sensory function:
• is due to loss of ulnar & medial
antebrachial cutaneous nerves
• sensory loss to the ulnar side of the:
 forearm
 hand
 ulnar 1.5 digits

120. Claw hand and sensory distribution of ulnar nerve

121. Brachial plexus compression syndrome
• caused by compression of the
neurovascular structures in the
cervicoaxillary region
• may be congenital or acquired

122. Brachial plexus compression syndrome (contn.)
• neurovascular structures involved are:
 subclavian vessels
 brachial plexus

123. Brachial plexus compression syndrome (contn.)
• subdivided into:
 scalene syndrome or cervical rib syndrome
 costoclavicular syndrome
 hyperabduction syndrome

124. Scalene syndrome
• caused by narrowing of interscalene
space by:
 a cervical rib
or
 a ligamentous structure

125. Scalene syndrome (contn.)
• condition occurs in about 1% of the
population
• cervical rib narrows the interscalene space

126. Scalene syndrome (contn.)
• sometimes there is no bony contact
between the cervical rib & the first rib
• instead, this site is occupied by a
ligamentous structure

127. Scalene syndrome (contn.)
• trunks of the brachial plexus & subclavian
artery traverse this space
• narrowing of the space causes
compression of the neurovascular
structures from below & behind

128. Cervical rib
forming complete
bony union with
first rib – note
neurovascular
bundle passing
behind the
anterior scalene
muscle

129. Ligamentous
structure
connecting the
cervical rib
to the first rib

130. Scalene syndrome (contn.)
• symptoms include:
 pain radiating down the arm, chiefly on
the ulnar side of the hand
 ischemic muscle pain (caused by
poor blood supply) in the upper limb

131. Costoclavicular syndrome:
• is compression of neurovascular bundle
between first rib & clavicle
• caused by narrowing of the costoclavicular
space

132. Costoclavicular syndrome (contn.):
• narrowing of this space is rare
• condition common in individuals with:
 drooping shoulders
 retracted shoulders (due to carrying heavy
loads)
 a previous clavicular fracture

133. Costoclavicular syndrome (contn.):
• symptoms similar to those associated with
scalene syndrome
• may include signs of venous stasis due
compromised return through subclavian
vein

134. Costoclavicular syndrome – note compression of
neurovascular bundle between clavicle & first rib

135. Hyperabduction syndrome:
• compression of neurovascular bundle
below pectoralis minor & coracoid process
• rare condition

136. Hyperabduction syndrome (contn.):
• condition precipitated by maximum
abduction or elevation of the arm on
the affected side
• symptoms include radiating pain in the
upper limb

137. Hyperabduction syndrome - bundle compressed beneath tendon of
pectoralis minor under coracoid process