Download brachial plexus

BRACHIAL PLEXUS
Abraham A.A. Osinubi
MBBS (Ibadan)
M.Sc. Anatomy (Lagos)
Ph.D. Anatomy (Lagos)
FACE (USA)
1
Definition

The brachial plexus is a somatic
nerve plexus formed by
intercommunications among the
ventral rami of the lower four
cervical nerves (C 5 - C 8) and the
greater part of ventral ramus of
first thoracic nerve (T 1)
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Functions
1. The plexus is responsible for
the motor innervation to all of the
muscles of the upper limb with
the exception of the trapezius
& levator scapula
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2. The brachial plexus supplies all of the
cutaneous innervation of the upper limb
with the exception of
the area of the axilla (supplied by the
intercostobrachial nerve)
an area just above the point of the
shoulder (supplied by supraclavicular
nerves)
the dorsal scapular area which is
supplied by cutaneous branches of
dorsal rami
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 The
brachial plexus communicates
with the sympathetic trunk by
communicantes that join all the
roots of the plexus and are
derived from the middle &
inferior cervical sympathetic
ganglia & the first thoracic
sympathetic ganglion
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Variations
Prefixed Brachial Plexus
– Occurs when the C 4 ventral ramus
contributes to the brachial plexus
– Contributions to the plexus usually come
from C 4 - C 8 + T1 is reduced
Postfixed Brachial Plexus
– Occurs when the T 2 ventral ramus
contributes to the brachial plexus
– Contributions to the plexus usually come from
C 6 - T 2 + contribution of C5 is reduced
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•Formation
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Roots
The ventral rami of spinal
nerves C5 to T1 are referred
to as the roots of the plexus
Lie behind scalenus anterior
muscle
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Trunks
Shortly after emerging from the
intervertebral foramina , the 5 roots unite
to form 3 trunks
The ventral rami of C5 & C6 unite to
form the Upper Trunk
The ventral ramus of C7 continues as
the Middle Trunk
The ventral rami of C8 & T 1 unite to
form the Lower Trunk
Emerge from lateral border of scalenus
anterior & cross post triangle
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
10 
Divisions
 Each trunk splits into an anterior
& a posterior division
 The anterior divisions usually
supply flexor muscles
 The posterior divisions usually
supply extensor muscles
Behind the clavicle
Cords
The anterior divisions of the upper &
middle trunks unite to form lateral cord
The anterior division of lower trunk
forms the medial cord
All 3 posterior divisions from each of 3
cords all unite to form posterior cord
The cords are named according to their
position relative to the axillary artery
At the outer border of first rib
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Terminal Branches (I)
 (n=5). Mixed nerves containing sensory
& motor axons
 Musculocutaneous n. Derived from
lateral cord (C5,6,7)
 Innervates muscles in flexor
compartment of arm
 Carries sensation from lat (radial)
side of forearm
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Terminal Branches (II)
Median n. Derived from lateral & medial cords
– Lat root= C6,7; Med root= C8,T1
– Motor innervation-most of flexor muscles in
forearm & intrinsic muscles of thumb (thenar
m.)
– Sensory innervation from lateral (radial) 3½
digits
Ulnar n. Derived from the medial cord
C7,C8,T1
– Motor innervation mainly intrinsic muscles of
hand
– Sensory innervation- medial (ulnar) 1½ digits
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Terminal Branches (III)
Axillary n. Derived from the posterior cord
– C5,6
– Motor innervation- deltoid & teres minor
– Sensory innervation- skin just below the point
of the shoulder
Radial n. Derived from the posterior cord
– C5-C8,T1
– Called “Great Extensor Nerve”: innervates
extensors of elbow, wrist & fingers
– Sensory innervation- dorsum of the hand on
the radial side
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•BRANCHES
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 From
the Roots
 Dorsal Scapular nerve
 Derived
from C5
 Motor nerve to the Rhomboideus major
& minor muscles
 Long
Thoracic nerve
 Derived
from C5,6,7
 Innervates
the serratus anterior muscle
 Nerves
to scaleni & longus colli (C5-8)
 Branch to phrenic n (C5)
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From the Upper Trunk
 Nerve to subclavius muscle (C5,6)
 Suprascapular nerve (C5,6)
 Innervates supra & infraspinatus
muscles

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
From the Lateral Cord

Lateral pectoral nerve
(C5,6,7) innervates pectoralis major
(clavicular or upper head) & pectoralis
minor

Lateral root of the median nerve
(C6,7)
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From the Medial Cord
Medial pectoral nerve (C8,T1)
innervates pectoralis major & minor
Medial cutaneous nerve of the arm
(medial brachial cutaneous) (C8,T1)
innervates the medial portion of the arm
Medial cutaneous nerve of the
forearm (medial antebrachial
cutaneous) (C8,T1) innervates the
medial half of the forearm
Medial root of the median nerve
(C8,T1) contributes to the median nerve
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Note
The
medial & lateral pectoral
nerves often join together to act
as a single nerve innervating
both the pectoralis major &
minor muscles
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Applied & Clinical Anatomy
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





Shoulder
• ABD & LAT/ROT – C5
• ADD & MED/ROT – C6,7,8
• FLEX & EXT- C6,7,8
Elbow
• FLEX- C5,6
• EXT- C7,8
Supination (Med n) & Pronation (M-C n)
• C6,7
Wrist
• FLEX- C6,7
• EXT- C6,7
Fingers
• FLEX- C6,7
• EXT- C7,8
Hand (Intrinsic muscles)- T1
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NERVE
Long Thoracic
(C5,6,7)
Suprascapular
(C5,6 )
Axillary
(C5,6)
MOTOR DEFICITS
Winged ScapulaSerratus Anterior
Difficult to initiate shoulder
abduction – Supraspinatus
Difficult abducting arm to
horizontal – Deltoid
Loss of shoulder roundness –
Deltoid
Musculocutan.
(C5,6,[7])
SENSORY
None
None
Lateral side
of arm;
below point
of shoulder
Lateral
Very weak flexion of elbow jointforearm
Biceps & Brachialis
Weak supination of
sup radioulnar joint –Biceps
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NERVE
Radial
(C5 - T1)
MOTOR DEFICITS SENSORY DEFICITS
Posterior aspect of arm &
Drop Wrist –
forearm;
Extensor carpi radialis
Radial 2/3 of dorsum of
longus & brevis,
hand & proximal parts
Ext. carpi ulnaris
of dorsal surfaces of
lateral 3½ fingers
Difficulty making a
fist - synergy
between wrist
extensors and
finger flexors
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Median
(C5 - T1)
at Elbow
Pronation of radioulnar jointsPronator teres & quadratus
Weak wrist flexion - Fl. Carpi radialis
Weakened opposition of thumb thenar muscles
Radial portion
of palm;
palmar
surface &
tips of radial
3½ digits
“Ape Hand”- thumb hyper extended
and adducted - thenar muscles
“Papal Hand” Loss of flexion of I.P.
joints of thumb & fingers 2 & 3 Fl. pollicis longus; Fl. digit.
superficialis, Fl. digit profundus
Median
(C5 – T1)
at Wrist
Weakened opposition of thumb thenar muscles
“Ape Hand”- thumb hyper extended
and adducted - thenar muscles
Palmar surface
& tips of
radial 3½
digits 25
Ulnar
“Clawing” of fingers 4 & 5- M.P. joints
(C8, T1)
hyper extended; P.I.P. Flexed at Elbow
Interossei & Lumbricals
Loss of abduction & adduction of M.P
joints of fingers –Interossei
Ulnar and
dorsal
aspect of
palm and
of ulnar 1½
digits
Thumb - abducted and extended adductor pollicis
Loss of flexion of D.I.P. joints of fingers 4
& 5 - Fl. digit profund.
Ulnar
(C8, T1)
at Wrist
“Clawing” of fingers 4 & 5- M.P. joints
hyper extended; P.I.P. Flexed Interossei & Lumbricals
Loss of abduction & adduction of M.P
joints of fingers – Interossei
Thumb - abducted & extended - adductor
pollicis
Ulnar and
dorsal
aspect of
palm and
of ulnar 1½
digits
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• UPPER AND LOWER ROOT LESIONS
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Lesion
Motor Deficits
Sensory Deficits
Nerves
Erb’s
Palsy
(C5,6)
Loss of abduction,
flexion & rotation at
shoulder; Weak
shoulder extension
– deltoid, rotator cuff
Posterior &
lateral aspect of
arm - axillary n.
Axillary,
Suprascapular,
Upper & Lower
subscapular
Very weak elbow
flexion and supination
of radioulnar joint –
biceps brachii &
brachialis
Radial side of
Forearm- m/c n.
Thumb & 1st
finger –Superf br.
of radial; digital
brs–Median n.
Musculocutaneous;
Radial n. brs. to
supinator &
brachioradialis
muscles
Susceptible to shoulder
dislocation - loss of
rotator cuff muscles
“Waiter’s Tip”positionarm add, elbow ext,
wrist flex
Suprascapular,
Upper & Lower
subscapular
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Lesion
Motor Deficits
Klumke’s Loss of opposition of
Palsy
thumb -Thenar
(C8,T1)
muscles
Loss of adduction of
thumb - Adductor pollicis
Sensory Deficits
Ulnar side of
Forearm &
Hand &
ulnar
1½ digits
Nerves
Thenar branch of
Median
Ulnar nerve
Ulnar & Median
Loss of abduction and
adduction of M.P.
joints; flexion at M.P.
& extension of I.P.
joints. Lumbricals &
interossei
Very weak flexion of
P.I.P. & D.I.P. joints. Fl.
Digit. Super. & Profund.
Ulnar & Median
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There are 4 types of nerve injuries:
Avulsion: the nerve is torn from the spine.
Rupture: the nerve is torn but not where it
attaches to the spine.
Neuroma: the nerve has tried to heal itself, but
scar tissue has grown around the injury. The
scar tissue puts pressure on the injured nerve.
As a result, the nerve cannot conduct signals to
the muscles.
Praxis: the nerve has been damaged but not
torn. These injuries heal on their own. If your
patient has praxis, you should see improvement
within 3 months.
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 Thank
you and have a
wonderful day
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