This document provides an overview of the brachial plexus and its main branches. It begins by discussing the formation of spinal nerves from the spinal cord. It then explains how the brachial plexus is formed by the union of the anterior primary rami of cervical and thoracic spinal nerves. The main branches of the brachial plexus including the cords, trunks, and major nerves are described. Common injuries to the brachial plexus and clinical presentations of injuries involving different nerve roots are summarized. Detailed information is provided on the course and distribution of the median and ulnar nerves.

1. BRACHIAL PLEXUS & ITS
MAIN BRANCHES
DR. G.KAMAU

2. Objectives
• Spinal cord &Formation of spinal nerve
• Formation of brachial plexus
• Brachial plexus palsies
• Main nerves of brachial plexus &their
distribution
• Palsies of the main nerves of brachial plexus.

3. Spine cord &Spine nerves formation
• Spine cord is part of central nervous system together with
the brain. But unlike brain, the grey matter is central & “H”
shaped , consisting of :- anterior/Ventral horn which is
motor somatic efferent.
-posterior/dorsal horn which is sensory
somatic afferent
Lateral horn in thoracic spine representing the
sympathetic autonomic system.
• The white matter is peripheral and contains descending
&ascending tracts of nerve fibres.
• *(In the brain,the grey matter cells of cerebral cortex are
outer)

6. Spinal nerve & nerve plexus
• Spinal nerve is a mixed spinal nerve containing mainly both motor efferent
,sensory afferent nerves .
• It arises from Anterior(motor) grey horn cells (which are destroyed in polio
myelitis) &Posterior/dorsal (sensory) grey horn cells (which are affected in
Tabes Dorsalis due to syphylis) by rootlets from a spinal cord segment which
join to form:-
• Anterior(ventral) root-which is efferent motor
• Posterior(dorsal) root which is afferent sensory from dorsal root
ganglion(DRG) which contain cell bodies of bipolar neurones with sensory
endings peripherally & centrally to posterior horn cells.
• Posterior & anterior roots unite to form spinal nerve.

8. • Spinal nerve immediately divides into:-
• Posterior(dorsal) primary rami which is smaller , supplies the back (spine,muscles,&skin)
Anterior (ventral) primary rami which is bigger , supplies the trunk (laterally &anteriorly) &the
limbs .Most of anterior primary rami merge as to form regional nerve plexus :-
• 1)cervical plexus.
• 2)Brachial plexus.
• 3)Lumbar plexus.
• 4)Sacral plexus.
• The spine nerve also communicates with sympathetic system ganglia in thoracic spine
segments via white rami communicantes containing preganglionic fibres connecting
them to the spine ,&grey rami communicantes postganglionic fibres .

13. Brachial plexus
• Is like network of nerves to upper limb formed by union of Anterior
(ventral) primary Rami C5C6C7C8 & T1.Occassionally C4 rami
Contributes to C5 (pre-fixed) or T2 rami to T1(post-fixed). Close to
ther exit at inter-vertebral foreman, they receive grey rami
communicantes postganglionic from sympathetic ganglia. The
roots & rami lie between anterior & middle scalene muscles .This
union forms :-
• Three Trunks passing downwards &laterally between scalenus
anterior & medius,above subclavian vessels , in posterior neck
triangle behind sternocleidomastoid posterior border & above
clavicle as :-
• 1)upper trunk:-By C5C6 anterior primary rami.
• 2)middle trunk:-By C7 anterior primary rami alone.
• 3)lower trunk :-By C8T1 anterior primary rami.

14. Brachial Plexus: Schema

21. • Trunks divide into anterior &posterior divisions (3x2). All divisions lie behind the
clavicle. No branches arise from divisions.
• All Posterior divisions merge to form posterior cord which main nerves are radial
nerve , axillary nerve , thoraco-dorsal nerve, upper &lower subscapular nerves
supplying posterior extensor compartment muscles.
• Anterior division of lower trunk form medial cord which main nerves are ulnar
nerve, medial pectoral nerve, medial head of median nerve &medial cutaneous
nerve of arm & forearm.
• Anterior divisions of upper & middle trunks merge to form lateral cord which
main nerves are musculo-cutaneous nerve which ends as Lateral cutaneous nerve
of the forearm , lateral pectoral & lateral head of median nerve .
• The Three Cords lie in axilla & are so named according to their relationship to 2nd
&3rd parts of axillary artery in the axilla which they encroach.The cords split into
the nerves in the lower part of axilla.The posterior cord supply extensor
compartment . Medial &lateral cords supply the flexor compartment.

22. Supraclavicular & infraclavicular
branches of brachial plexus
• :-Supraclavicular
• Roots:-1)Long thoracic nerve of Bell- C5C6C7 to
Serratus anterior.(winged scapula)
2)Dorsal scapular nerve C5 to Rhomboids
&levator scapulae.
3)C5 branch to phrenic nerve (phrenic nerve
roots areC3C4C5 main one being C4)
4)Scalene branches.
Trunks:-1)Suprascapular nerve from upper trunk to
Supraspinatus & infraspinatus.
2)nerve to subclavius.

23. • Infraclavicular branches from Cords:-
• Lateral cord:-1)Musculo-cutaneous nerve
supplying coracobrachialis,biceps &greater part
of brachialis.It terminates as lateral cutaneous
nerve of forearm.
2)Lateral pectoral nerve (large than
medial pectoral) which pierces clavipectoral
fascia to the deep surface of P.major which it
supplies together with P.Minor. 3)Lateral
cutaneous nerve of forearm
4)Lateral branch to form median nerve

24. Musculocutaneous Nerve

25. Nerves of Upper Limb

26. • Medial cord:-1)Ulnar nerve.
2)Medial pectoral nerve (smaller than lateral pectoral) which pierces
P.Minor which it supplies >to P. Major which it also supplies.
3)Medial cutaneous nerves of arm &forearm. 4) medial branch to
form median nerve.
5)medial cutaneous nerve of forearm
• Posterior cord:-1)Radial nerve
2)Axillary nerve
3) Superior &inferior subscapular nerves to subscapularis&T.Major
4)Thoraco-dorsal nerve C6C7C8 along posterior wall of axilla to
Latissimus dorsi
Roots:-Lie in the neck between scalene anterior &middle
Trunks in posterior neck triangle behind SCM
Divisions behind the clavicle.
Cords in the axila
*NB P.Major Is supplied by both Lateral &medial pectoral, but P.minor by medial
pectoral alone.

27. Brachial plexus injuries
• Common in injuries eg high velocity motor cycle accidents &horse riders
where one is thrown off landing on the side of neck,shoulder &head
forcing the two apart putting strain on the roots. Obstetric delivery
injuries in new born.
• Could be:-1)Root avulsion from spine cord-no recovery and not amenable
to surgery (neurotomesis).
-2)Trunks rupture distal to intervertebral foramina.May not
recover but surgical repair is accessible (neurotomesis).
-3)Traction injury>Neuropraxia , axonotomesis or neurotomesis.
• Upper roots injury C5C6>Erb-Duchenne palsy.>Paralysis of deltoid&
other muscles of the shoulder(>Paralytic dislocation of the shoulder),
biceps ,Brachialis (Inability to flex elbow or supinate the forearm).The arm
hangs limply on the side with forearm pronated and palm facing
backwards as “policeman, porter or waiter tip position”.

28. • Lower root injuries (Klumpke’s palsy) are less common .Mainly
affecting intrinsic hand muscles>clawing ,&loss of sensation on
medial side of arm(T1).May be associated with Horner’s syndrome
(Ptosis &pupil constriction) where cervical sympathetic ganglion is
affected .
• Total brachial injury with C5-T1 injury > Paralytic dislocation of the
shoulder.
• Thoracic outlet syndrome affecting lower roots> Loss of sensation
on medial side of arm &ulnar nerve palsy in association with
vascular insufficiency due to compression of subclavian vessels.
Could be due to cervical rib or its fibrous band,compression
between scalene muscles,#s clavicle.
• Pancoast syndrome due to apex of lung primary or secondary
cancers may produce similar syndrome involving of lower roots.
• Radiation neuritis of brachial plexus

34. Median nerve (C6C7 C8 T1)
• Median nerve C6C7C8T1 is formed by medial &lateral cords branches that
embrace the 3rd part of axillary , the nerve so formed being on
anterior/lateral side of axillary artery.
• The nerve in the arm descends lateral to brachial artery.At the insertion of
coracobrachialis ,it crosses to medial side of brachial artery lying at the
elbow cubital fossa over brachialis deep to bicipital aponeorosis.At the
elbow it gives muscular branches to PRT,FCR FDS, &palmaris longus.
• It then descends to the forearm passing between deep & superficial heads
of pronator teres where it gives anterior interosseous nerve lying on
interrosseous membrane supplying mainly FPL & FDP lateral part (patient
can not make O sign when it is paralysed & index finger adopts a
“pointing” position ).
• As it ascends to the wrist lying between FDP &FDS, it gives a palmar
cutenous branch to supply the thenar area. It enters the carpal tunnel
behind the flexor retinaculum anterior to carpal bones.It may be
compressed at carpal tunnel >carpal tunnel syndrome.Also very often
severed at wrist together with the long flexor tendons at the wrist.

35. Median Nerve

36. Arteries and Nerves of Upper Limb

37. Nerves of Upper Limb

38. Ligament of Struthers
• Coracobrachialis is like three adductors in lower limb.In
man it is undeveloped as other stronger adductors of
the arm have taken over
• But persistence of lower head occasionally may be
present as Ligament of Struthers projecting from
supratrochlear spur on anteromedial side of lower
humerus to medial epicondyle.
Beneath the ligament the median nerve or brachial artery
or both ,may pass through.Pressure by ligament of
Struthers may cause median nerve palsy together with
irritative spasm of brachial artery.

39. Muscles of Arm: Anterior Views

40. Median nerve cont-
• In the palm, it becomes flattened giving branches
to:-1)Thenar muscles FPB,Abductor pollicis
brevis,opponens pollicis, branches to 2nd & 3rd
radial lumbricals.
2)Digital branches to lateral 3 ½
lateral fingers palmar surface.
• Median nerve palsy >wasting of thenar muscles
with inability to abduct the thumb & loss of
sensation to the 3 ½ lateral fingers it supplies.

43. Cutaneous Innervation of Wrist and Hand

48. Ulnar nerve (C7C8T1)
• Arises from the medial cord running distally on medial side of axillary artery lying between
It & axillary vein. At the middle of the arm it pierces the medial intermuscular septum descending at
ulna groove between medial epicondyle & olecranon.>cubital tunnel syndrome
• It descends between the two heads of FCU (Canal of Osborne) which it supplies.
• It descends straight on the medial side of forearm medial to ulna artery , lying on FDP which it
supplies its medial half. About 5cm to the wrist it gives dorsal cutaneous branch to dorsal aspect
of medial 1 ½ little & ring fingers.
• At the wrist it lies lateral to pisiform on flexor retinaculum (Canal of Guyon *NB it does not pass
through carpal tunnel) posteromedial to ulna artery to enter the palm supplying hypothenar
muscles (flexor,abductor,&opponens digiti minimi),Interrossei,Adductor pollicis &3rd &4th medial
lumbricals.
• It sends digital sensory branches to medial 1 ½ digits of palmar surfaces of little &ring fingers.
• Ulnar nerve palsy > wasting of hypothenar muscles, loss of sensation to the medial little &ring
fingers.The dorsal interrossei are bigger and abduct the fingers (DAB).The palmar interrossei are
smaller & addduct the fingers(PAD).The interrosei & lumbricals join the extensor expansion and
together flex MP joint &extend the IP joints. >In ulna nerve palsy there is clawing at IP joints of
little & ring fingers.Also there is loss of thumb adduction towards the index finger in the palmar
plane.

49. Ulna Nerve

52. Radial nerve C5C6C7C8T1.
• The largest branch of brachial plexus as it is formed by all posterior divisions forming the posterior
cord from which the radial nerve arises posterior to 3rd part of axillary artery.
• It descends posteriorly between the long & medial heads of triceps infront of teres
major,(Triangular space ;-base is teres major superiorly. Medial border is long head of triceps. ) .
• It descends obliquely over the back of humerus spiral groove between the medial & lateral heads of
triceps.
• At lower 1/3 of humerus it pierces lateral inter muscular septum to enter anterior compartment of
the arm between brachialis & brachioradialis.
• At the lateral epicondyle it divides into deep posterior interrosseous which winds around the
radius to pass between the deep & superficial heads of supinator (the arcade of Frohse is a
thickening on proximal edge of superficial head of supinator &may compress the posterior
interrosseous nerve).The nerve is often injured at injuries at elbow around PRUJ. Because
Brachioradialis &ECRL are spared,the patient can extend the wrist with radial deviation, but can
not extend the MP joints.In total radial nerve palsy eg in #s of humerus at spiral groove the patient
can not extend both wrist and MP joints. “Crutch radial nerve palsy &Saturday night radial nerve
palsy in alcoholism & drug overdose.
• The superficial branch continues deep to brachioradialis .Above the wrist it emerges as cutaneous
branch to the dorsum of hand , web space between the thumb and index fingers & dorsal aspect
of the lateral 3 ½ fingers.
• The radial nerve supplies extensor compartment muscles (triceps, lateral part of
brachialis,brachioradialis, ECRL,anconius). The posterior interrosseous supplies supinator &
abductor policis longus .

53. Muscles of Arm: Posterior Views

54. Radial Nerve in Arm and Nerves of Posterior Shoulder

55. Radial Nerve in Forearm

59. Axillary nerve (C5C6)
• The axillary nerve is a branch of posterior cord winds
around the surgical neck to enter through
quadrangular space (medial border is long head of
triceps, lateral border is surgical neck of humerus
,superior border is Teres minor & inferior border teres
major.)It is accompanied by posterior circumflex
humeral vessels.
• Muscular branches deltoid & teres minor. Cutaneous
branch to “regimental badge area” palm-sized area
over deltoid where sensation may be lost in #s of
surgical neck associated with axillary nerve palsy
>inability for deltoid to abduct & later loss of shoulder
bulge .

63. Axilla (Dissection): Anterior View