Brachial plexus

The brachial plexus
 Formation
 Supraclavicular portion
 Trunks
 Divisions
 Infraclavicular portion
 Cords
 Branches

The brachial plexus
 The brachial plexus is a
network of nerves that
supply the upper limb

The brachial plexus
 extends from the neck
into the axilla

Formation
 It is formed by five
roots from the anterior
(ventral) primary rami
of C5,6,7,8, andT1

Formation
 the roots of the
brachial plexus should
not be confused with
the ventral and dorsal
roots which unite to
form the spinal nerves
dorsal &
ventral
roots of
a spinal n.
The ventral
rami form
the roots of
the brachial
plexus

Supraclavicular portion
 The roots lie in the
neck between scalenus
anterior and scalenus
medius muscles
Scalenus anterior
Scalenus medius

 C5 & C6 unite to form
the upper trunk

 C8 &T1 unite to form
the lower trunk

 C7 continues as the
middle trunk

Trunks of the brachial plexus
 The trunks lie in the posterior triangle of
the neck and can be felt in the angle
between the clavicle and
sternocleidomastoid muscle
clavicle

 The inferior trunk lies
on the first rib
posterior to the
subclavian artery
Inferior trunk

Divisions of the brachial plexus
 Behind the clavicle,
each trunk divides into
anterior and posterior
divisions

 the anterior divisions
supply anterior (flexor)
parts while the
posterior divisions
supply posterior
(extensor) parts of the
upper limb

Infraclavicular portion
 The three posterior
divisions unite to form
the posterior cord
Posterior cord

 the anterior divisions
of the upper and
middle trunks unite to
form the lateral cord
lateral cord

 the anterior division of
the lower trunk
continues as the
medial cord
medial cord

Cords of the brachial plexus
 The cords are arranged
around the second part
of the axillary artery as
indicated by their
names.

Branches of the brachial plexus
 Each cord of the
brachial plexus divides
into a number of
branches, 2 of them
are terminal

 there are also a
number of
supraclavicular
branches

Branches of the roots
 Dorsal scapular (C5)
which supplies
rhomboids muscles
and levator scapula

 Nerve to subclavius (C5 & 6)
which descends in front of the
brachial plexus and the
subclavian artery in the neck, it
may give a contribution to the
phrenic nerve (C5) this branch,
when present is called the
accessory phrenic nerve.

 The third branch is the
long thoracic nerve
(C5,6, & 7) descends
behind the brachial
plexus and supplies
serratus anterior
muscle

Suprascapular nerve
 From the upper trunk
arises the
suprascapular nerve

Suprascapular nerve
 The suprascapular
nerve passes laterally
across the neck, then
through the
suprascapular notch in
the scapula to supply
supraspinatus and
infraspinatus muscles

Infraclavicular branches
 The infraclavicular
branches are derived
from the cords
 Each cord divides into
2 terminal branches.

Branches of the lateral cord
 The lateral cord has 3
branches mainly the
lateral pectoral nerve
and 2 terminal
branches, the
musculocutaneous and
the medial root of the
median nerve

Lateral pectoral nerve
 The lateral pectoral
nerve pierces the
clavipectoral fascia to
supply pectoralis major
muscle

Lateral pectoral nerve
 sends a communicating
loop to the medial
pectoral nerve, through
which it supplies
pectoralis minor muscle
Axillary a.
Pectoralis minor
medial
pectoral n.
laterall
pectoral n.
Medial
cord
lateral
cord
posterior
cord
Axillary v.
communicating loop

Musculocutaneous nerve
 pierces coracobrachialis
muscle, supplying it
before doing so

 it then supplies the
muscles of the flexor
(anterior)
compartment of the
arm mainly biceps
and brachialis
 therefore it is known
as the BBC nerve

 It ends by
becoming
the lateral
coetaneous
nerve of the
forearm

Lateral root of the median nerve
 The lateral root of the
median nerve is the
direct continuation of
the lateral cord

Median nerve
 The median nerve
arises by medial and
lateral roots from the
corresponding cords of
the brachial plexus

Median nerve
 the medial root crosses
the axillary artery to
join the lateral root so
the median nerve is
formed at first lateral
to the axillary artery.

Median nerve
 The median nerve has
no branches in the
axilla and is
responsible for the
supply of the flexor
compartment of the
forearm and the palm.

Branches of the medial cord
 The medial cord has 5
branches
 the ulnar nerve and
medial root of the
median nerve are its
two terminal branches
Ulnar n.

Medial pectoral nerve
 The medial pectoral
nerve passes through
pectoralis minor
supplying it then it
supplies pectoralis
major
Axillary a.
Pectoralis minor
medial
pectoral n.
laterall
pectoral n.
Medial
cord
lateral
cord
Axillary v.
axillary a. axillary v.
Medial pectoral n.
Pectoralismajor

Medial cutaneous nerve of arm
 The medial cutaneous
nerve of the arm, is a
small nerve that runs
medial to the axillary
vein and supplies the
skin over the medial
side and front of the
arm
Axillary a.

Medial cutaneous nerve of arm
 communicates with
the intercostobrachial
nerve

medial cutaneous nerve of the forearm
 runs between the
axillary artery and vein
and supplies skin of the
medial side of the
forearmAxillary a.

medial cutaneous nerve of the forearm
Runs between the axillary artery and vein
superficial to the ulnar nerve

Ulnar nerve
 is the largest branch of
the medial cord
 runs between the
axillary artery and vein
but at a more posterior
plane than the smaller
medial cutaneous
nerve of the forearm
Axillary a.

Ulnar nerve
 receives a branch from
the lateral cord in more
than 90% of cases
 has no branches in the
axilla
 is mainly concerned
with the innervation of
the palm.

Medial root of the median nerve
 crosses the axillary
artery to form the
median nerve lateral to
the artery
Axillary a.

 Note that the
musculocutaneous,
median, and ulnar
nerve form the letter
M, which serves as the
key to the brachial
plexus

Branches of the posterior cord
 The posterior cord of
the brachial plexus has
5 branches
 the axillary and radial
nerves are its 2
terminal branches.

Upper and lower subscapular nerves
 The upper and lower
subscapular nerves
supply the upper and
lower parts of
subscapularis
muscle

Lower subscapular nerve
 the lower
subscapular nerve
supplies teres major
muscle in addition
to suscapularis

Thoracodorsal nerve
 Runs between the
subscapular nerves, it
runs down on
subscapularis
towards latissimus
dorsi which it
supplies, it
accompanies the
subscapular vessels.

Axillary nerve
 It is inappropriately
named since it supplies
nothing in the axilla
 The first thing it does is
to quit the axilla by
passing backwards
through the posterior
wall of the axilla

Axillary nerve
 It leaves the axilla through
the quadrangular space
accompanied by the
posterior circumflex humeral
vessels just below the capsule
of the shoulder joint to which
it sends an articular branch
(so it is sometimes called the
circumflex nerve)

Axillary nerve
 It winds around the
surgical neck of the
humerus deep to
deltoid muscle which it
supplies, it also
supplies teres minor,
and the upper lateral
cutaneous nerve of the
arm

Radial nerve
 The radial nerve
provides the major
nerve supply of the
extensor muscles of
the upper limb (arm
and forearm)

Radial nerve
 It lies behind the axillary
artery on the glistening
tendon of latissimus dorsi
musclelatissimus
dorsi tendon

Radial nerve
posterior
cord
triceps
(long head)
posterior
cutaneous of arm
triceps
(medial head)
Branches in the axilla

Radial nerve
 It leaves the axilla
posteriorly through a
triangular space
between the humerus,
teres major, and the
long head of triceps

Variants of normal anatomy –
Expanded plexus
 Prefixed plexus – substantial contribution from
C4 with smallT1 contribution.
 Postfixed plexus – MajorT2 contribution with
small C5 contribution.

Brachial plexus
injuries
Etiologies
 traffic accidents
 birth injuries
 humerus luxations
 brachial plexus neuritis
 stab and bullet wounds
 tumors (especially lung cancer)
 cervical rib, fibrous band from C7 (neurogenic
thoracic outlet syndrome)

Principles of Localization
 Certain sites are prone to nerve
entrapments/injuries
 Nerve opposing bone
 Ulnar nerve at the elbow
 Closed spaces
 Carpal tunnel
 Adjacent structures
 Median nerve at the elbow, adjacent to the
brachial artery

Principles of localization
(cont.)
 Order in which branches arise
 Movements at specific joints
 Single nerve
 Elbow extension
 Radial
 Multiple nerves
 Elbow flexion
 Musculocutaneous
 Radial

Brachial Plexus
Injuries
 Upper Lesions of the Brachial Plexus
(Erb’s Palsy): resulting from excessive
displacement of the head to opposite side
and depression of shoulder on the same side.

This causes excessive traction or even
tearing of C5 and 6 roots of the
plexus. It occurs in infants during a
difficult delivery or in adults after a
blow to or fall on shoulder.

 Effects:
Motor: paralysis of
 the supraspinatus,
 infraspinatus,
 subclavius,
 biceps brachii,
 part of brachialis,
 coracobrachialis;
 deltoid
 teres minor.
Sensroy: sensory loss on the lateral side of
the arm.

Deformity:
waiter tip postion
a. limb will hang by the side,
b. medially rotated by sternocostal part
of the pectoralis major;
c. pronated forearm (biceps paralysis)

Erb-Duchenne palsy (waiter's tip)

Lower Lesions of the Brachial Plexus
(Klumpke Palsy)
 traction injuries by excessive abduction of the
arm
 i.e. occurs if person falling from a height
clutching at an object to save himself or
herself.
 Can be caused by cervical rib.
 T1 is usually torn (ulnar and median nerves)

Motor Effects: paralysis of all the
small muscles of the hand.
Sensory effects: loss of sensation
along the medial side of the arm.
deformity: claw hand caused by
hyperextension of the
metacarpophalangeal joints and
flexion of the interphalangeal
joints.

Axillary Nerve
injury
Causes:
crutch pressing upward into the
armpit,
Downward shoulder dislocations
fractures of the surgical neck of the
humerus.

Motor effects:
Deltoid paralysis
teres minor paralysis.
Sensory effects:
loss of sensation at lower ½ of
deltoid
Deformity:
Wasting of deltoid

Radial Nerve injury
Injury in axilla :
 crutch pressing up into armpit
 drunkard falling asleep with one
arm over the back of a chair.
 fractures of proximal humerus.

 Motor effects:paralysis of
 triceps
 Anconeus
 extensors of the wrist
 Extensors of fingers.
 Brachioradialis
 supinator muscle
 Deformity: Wrist and finger
drop

Sensory effects :
small area of sansation loss
at arm and forearm
sensory loss over lateral part
of the dorsum of the hand
(lat. 3.5 fingers without distal
phalynges)

Injuries at Spiral Groove
Caused by fracture shaft of humerus.
 Motor effects: paralysis of
extensors of the wrist
Extensors of fingers

 Deformity:
Wrist and finger drop
 Sensory effects:
anesthesia is present over the dorsal
surface of the hand (lat. 3.5 fingers)

Median Nerve injury
Motor effects: paralysis of
pronator muscles
long flexor muscles of the wrist and
fingers,
Exception:
a. flexor carpi ulnaris
b. medial half flexor digitorum profundus.

Deformity:
apelike hand
1. thenar muscles wasted
2. thumb is laterally rotated and
adducted.
3. index and to a lesser extent the
middle fingers tend to remain
straight on making
4. Weakening of lat. 2 fingers

Sensory:
Sensory loss on the lat. 3.5
fingers on palmar side
Sensory loss over distal
phalynges of lat. 4 fingers on
dorsal surface

Ulnar nerve injury
 Motor effects: paralysis of
 flexor carpi ulnaris
medial half of the flexor digitorum profundus
All interossei
3-4 lumbricals
 loss of abduction and adduction of fingers
 Wasting of hypothenar

 Deformity:
partial claw hand
 Sensory effects :
Sensory loss over 1.5 fingers on both
surfaces

CARPAL TUNNEL
 TUNNEL FORMED BETWEENTHE CONCAVITY OFTHE CARPAL BONES
AND A LIGAMENTTHAT COVERSTHIS( FLEXOR RETINACULAM)
 TENDONS OFTHE FLEXORS PASSTHROUGH
 MEDIAN NERVEALSO PASSESTHROUGH
 CROWDEDTUNNEL
CARPALTUNNEL SYNDROME
- CAUSED DUETO COMPRESSIONOFTHE NERVE INTHETUNNEL
- CAUSES-
- 1. SWELLING OFTHETEDONS( OVERUSE)
- 2. PREGNANCY( EDEMA)
- 3. ARTHRITIS
SYMPTOMS-TINGLING OR NUMBNESS-LATERAL PART OF HAND,
WEAKNESS INTHUMB MOVEMENT
TREATMENT- REST, SPLINTING,ANTI-INFLAMMATORY DRUGS, SURGERY

Classification of Brachial
plexopathies
1)Supraclavicular(root and trunk) –
Upper plexopathy (upper trunk and root)
Middle plexopathy (middle trunk & root)
Lower plexopathy(lower trunk and root)
2)Retroclavicular (division)
3)Infraclavicular(cords and nerves)

Classification of Brachial
plexopathies
 Supraclavicular with regional predilection
1)Upper plexus
1) Burner syndrome
2) Rucksack paralysis
3) Classic post – operative paralysis
2)Middle plexus – No isolated pathology

 Lower Plexus
1)True neurogenicTOS
2) Post op disputed neurogenicTOS
3) Paramedian sternotomy plexopathy
4) Pancoast syndrome
 Other supraclavicular plexopathies.
- Root avulsions.
- Obstetric Brachial plexopathy

Site nonspecific brachial plexopathies
 1) Neuralgic amyotrophy
 2) Neoplastic brachial plexopathies
 3) Radiation induced.
 4)Traumatic
 5) Iatrogenic

Supraclavicular vs infra
Supraclavicular
 More common
 More often caused by closed traction injuries
– more lengthy lesions
 More severe
 Worse outcome

Upper plexopathy vs lower
Upper plexopathy
 More commonly due to demyelinating
conduction block
 Recovery better
Less axonopathy
Located closer to the muscles
Lesion mostly extraforaminal (amenable to
surgical repair)

Evaluation of Brachial
plexus
 History and Clinical examination
 Electrophysiological tests.
 Imaging and other ancillary tests –
angiogram, myelogram etc

Clinical evaluation
History
 Initial and subsequent symptoms – esp pain
 Circumstances
Trauma – sports, injections, accident
obstetrical
Rucksack, Post – operative
H/o malignancy or radiation

Clinical evaluation
 If trauma - what was the arm position on
impact?
Arm by side of body – C5, C6
Arm parallel to ground – C7
Arm above shoulder – C8T1
 Past medical history
 Family history

Examination
 Look for wasting with weakness – axonopathy vs
demyelinating.
 Pattern of deficits
Supraclavicular – segmental
Infraclavicular – more in territory of multiple
peripheral nerves of diff segments.

 Vascular assessment – carotid and radial pulse.
Any expanding mass, bruit or thrill near injury
site
 Concomitant injuries – fractures of bones
 Examine breast, lungs and for lymphnodes

Electrodiagnostic assessment
Advantages over clinical
1) Better localisation and characterisation
2) Subtle involvment in clincally normal muscle
3)To prove continuity when visible muscle movement is
lacking.
4) Clinically inaccessible muscles
5) Estimate lesion severity for current and future
comparisons.

 Being a complicated structure, no single study
can localize or characterize the lesion.
 Requires extensive NCS and NEE
 A regional approach may make it more
simpler.

Electrodiagnostic tests
 Nerve conduction studies
Motor
Sensory
 Needle Electrode Examination

General principles in EP
 Pathophysiologically
1) Axonal –
loss of continuity of axon –Wallerian degeneration-
conduction failure.
More severe lesion
2) Demyelinating - Conduction block or conduction
slowing.

Axon loss lesions
 Most common pathology in BP.
 Mostly in isolation (avulsion, neoplasm)
 Occasionally with demyelination (radiation
plexopathy, traumatic)

Edx features of axon loss
lesions
 Reduced CMAP/SNAP amp with preserved CV
and latencies.
 Absolute decrease in amp – less than normal
for lab
 Relative decrease in amp - < 50 % of amp on
C/L side.

NEE
 Most sensitive indicator of motor axonal loss.
 To know the proximal extend of lesion (where nerves
are difficult to assess)
 To know continuity and identify early reinnervation
when there is no muscle movement clinically.

A regional approach
 What will be the electrodiagnostic features if
each element of the brachial plexus is taken
seperately?
 Muscle domain of element
 CMAP/SNAP domain

 The muscle domain of a brachial plexus
element – muscles innervated by the motor
fibers contained within it.
 CMAP/SNAP domain – motor and sensory
fibers contained within that element and
whether they are assessable by NCS.
 CMAP domains are a subset of muscle
domains.

Treatment Most injuries recover without any Rx
 Rx is done in very highly specialized centers
 Surgical options
a. nerve transfers
b. nerve grafting
c. muscle transfers
d. free muscle transfers
e. neurolysis of scar around the brachial
plexus in incomplete lesions.

Brachial plexus

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