1. BRACHIAL PLEXUS Abraham A.A. Osinubi MBBS (Ibadan)
M.Sc. Anatomy (Lagos)
Ph.D. Anatomy (Lagos)
FACE (USA)

2. 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)

3. 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

4. 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

5. 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

6. Variations Prefixed Brachial Plexus Postfixed 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

7. Formation

8. Roots
The ventral rami of spinal nerves C5 to T1 are referred to as the roots of the plexus
Lie behind scalenus anterior muscle

9. 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

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

11. 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

12. 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

13. 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

14. 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

15. BRANCHES

16. Nerves to scaleni & longus colli (C5-8) Branch to phrenic n (C5)
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)

17. From the Upper Trunk
Nerve to subclavius muscle (C5,6)
Suprascapular nerve (C5,6)
Innervates supra & infraspinatus muscles

18. 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)

19. Medial pectoral nerve (C8,T1) innervates pectoralis major & minor
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

20. Note
The medial & lateral pectoral nerves often join together to act as a single nerve innervating both the pectoralis major & minor muscles

21. Applied & Clinical Anatomy

22. 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
Hand (Intrinsic muscles)- T1

23. NERVE
Long Thoracic (C5,6,7)
MOTOR DEFICITS
Winged Scapula-
Serratus Anterior
SENSORY
None
Suprascapular (C5,6 )
Difficult to initiate shoulder
abduction – Supraspinatus
Axillary
(C5,6)
Difficult abducting arm to
horizontal – Deltoid
Lateral side
of arm;
below point
of shoulder
Loss of shoulder roundness –
Deltoid
Musculocutan. (C5,6,[7])
Very weak flexion of elbow joint-
Biceps & Brachialis
Lateral
forearm
Weak supination of
sup radioulnar joint –Biceps

24. NERVE
Radial
(C5 - T1)
MOTOR DEFICITS
Drop Wrist –
Extensor carpi radialis
longus & brevis,
Ext. carpi ulnaris
SENSORY DEFICITS
Posterior aspect of arm & forearm;
Radial 2/3 of dorsum of hand & proximal parts of dorsal surfaces of lateral 3½ fingers
Difficulty making a fist - synergy between wrist extensors and finger flexors

25. Median
(C5 - T1)
at Elbow
Pronation of radioulnar joints-Pronator teres & quadratus
Radial portion of palm; palmar surface & tips of radial 3½ digits
Weak wrist flexion - Fl. Carpi radialis
Weakened opposition of thumb - thenar muscles
“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
(C5 – T1)
at Wrist
Palmar surface & tips of radial 3½ digits

26. Ulnar
(C8, T1)
at Elbow
“Clawing” of fingers 4 & 5- M.P. joints hyper extended; P.I.P. Flexed - Interossei & Lumbricals
Ulnar and dorsal aspect of palm and of ulnar 1½ digits
Loss of abduction & adduction of M.P joints of fingers –Interossei
Thumb - abducted and extended - adductor pollicis
Loss of flexion of D.I.P. joints of fingers 4 & 5 - Fl. digit profund.
at Wrist
Loss of abduction & adduction of M.P joints of fingers – Interossei
Thumb - abducted & extended - adductor pollicis

27. UPPER AND LOWER ROOT LESIONS

28. 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”position-
arm add, elbow ext,
wrist flex

29. Loss of opposition of thumb -Thenar muscles Sensory Deficits
Lesion
Klumke’s
Palsy
(C8,T1)
Motor Deficits
Loss of opposition of thumb -Thenar muscles
Sensory Deficits
Ulnar side of
Forearm &
Hand &
ulnar
1½ digits
Nerves
Thenar branch of Median
Loss of adduction of
thumb - Adductor pollicis
Ulnar nerve
Loss of abduction and adduction of M.P. joints; flexion at M.P. & extension of I.P. joints. Lumbricals & interossei
Ulnar & Median
Very weak flexion of
P.I.P. & D.I.P. joints. Fl.
Digit. Super. & Profund.

30. 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.

31. Thank you and have a wonderful day