brachial plexus

Plan

· 5 roots lie behind scalenus anterior muscles

· emerge between it and scalenus medius

· at this point, unite to form trunks

· upper - C5 + C6

· middle - C7

· lower - C8 + T1

· trunks cross lower part of posterior triangle of neck

· just behind clavicle, each trunk divides into 2 divisions

· anterior and posterior

· divisions unite to form cords

· lateral - upper and middle anterior

· medial - lower anterior

· posterior - all three posterior

· enter axilla above 1st part of artery

· embrace 2nd part of artery

· give off branches around 3rd part of artery

· roots and trunks are supraclavicular part

· cords and branches are infraclavicular part

Variations

· may be branch from C4 to C5

· if large, branch from T1 reduced or absent

· called prefixed type of plexus

· may be branch of T2 to T1

· if large, branch from C5 is reduced or absent

· called postfixed type of plexus

Relations

Neck

· lies in posterior triangle

· in angle between clavicle and sternomastoid

· crossed by

· supraclavicular nerves

· nerve to subclavius

· suprascapular vessels

· inferior belly of omohyoid

· external jugular v

Axilla

· lateral and posterior cords on lateral side of axillary a

· medial cord behind axillary a

· embrace 2nd part of artery and lie in positions suggested by name

Branches from roots

Dorsal scapular nerve (C5)

· nerve to rhomboids

· arises from posterior part of C5

· pierces scalenus medius

· runs deep to levator scapulae

· supplies both rhomboids

· gives branch to levator scapulae

Nerve to subclavius (C5,6)

· arises from anterior parts of C5 and C6

· passes down in front of trunks and subclavian vein

· enters posterior surface of subclavius

Long thoracic nerve (C5,6,7)

· nerve to serratus anterior

· arises from posterior parts of C5, C6 and C7

· branches from C5 and C6

· enter scalenus medius

· unite and emerge from lateral border

· pass down into axilla behind plexus

· C7 branch

· descends in front of scalenus medius

· joins C5-C6 trunk

· nerve forms on 1st digitation of serratus anterior

· passes down posterior to midaxillary line

· supplies muscle segmentally

· C5 to upper 2

· C6 to next 2

· C7 to lowest 4

Branches from trunks

Suprascapular nerve (C5,6)

· arises from upper trunk

· arises in posterior triangle

· passes backwards and laterally

· disappears beneath border of trapezius

· passes through suprascapular foramen

· under transverse scapular ligament

· supplies supraspinatus

· two branches

· descends lateral to scapular spine

· supplies infraspinatus

· two branches

Branches from lateral cord

Lateral pectoral nerve (C5,6,7)

· pierces clavipectoral fascia

· supplies clavicular fibres of pectoralis major

· communicates with lateral pectoral nerve

· thus supplies pectoralis minor

Musculocutaneous nerve (C5,6,7)

· runs obliquely down

· enters coracobrachialis 5 (3-8) cm distal to coracoid

· supplies it (C5,6)

· passes in plane between biceps and brachialis

· supplies them both

· emerges at lateral border of biceps tendon

· becomes lateral cutaneous nerve of forearm

· supplies radial border of forearm

Lateral head of median nerve (C6,7)

· continuation of lateral cord

· joined by medial head of median nerve

· two heads embrace artery

Branches from medial cord

Medial pectoral nerve (C8)

· arises behind axillary a

· enters deep surface of pectoralis minor and supplies it

· enters pectoralis major and supplies sternocostal fibres

Medial cutaneous nerve of arm (C8,T1)

· smallest and most medial of branches

· runs on medial side of axillary vein

· sometimes supplies skin over anteromedial upper arm

Medial cutaneous nerve of forearm (C8, T1)

· bigger nerve

· runs down between artery and vein

· runs in front of ulnar nerve

· pierces deep fascia halfway down arm with basilic v

· divides into anterior and posterior branch

· cross elbow on medial side of cubital fossa

· supplies skin on lower arm and ulnar forearm

Ulnar nerve (C7,8,T1)

· largest branch

· runs down between artery and vein

· behind medial cutaneous nerve of arm

· receives branch from lateral cord

· fibres given off in forearm as branch to FCU

Medial head of median nerve (C8,T1)

· continuation of medial cord

· crosses axillary a

· joins lateral head

Branches from posterior cord

Upper subscapular neve (C6,7)

· enters upper part of subscapularis

Thoracodorsal nerve (C6,7,8)

· nerve to latissimus dorsi

· runs down posterior axillary wall

· crosses lower border of teres major

· enters deep surface of lat dorsi

Lower subscapular nerve (C6,7)

· supplies lower part of subscapularis

· gives branch to teres major

Axillary nerve (C5,6)

· passes backwards through quadrilateral space

· between subscapularis and teres major

· between long head of triceps and humerus

· with posterior circumflex humeral vessels

· gives branch to shoulder joint

· lies against surgical neck of humerus

· divides into anterior and posterior branches

· anterior branch

· runs forwards around humerus

· with posterior circumflex humeral vessels

· enters deep surface of deltoid

· gives few cutaneous twigs

· posterior branch

· gives branch to teres minor

· winds around posterior border of deltoid

· supplies a few posterior fibres

· becomes upper lateral cutaneous nerve of arm

Radial nerve (C5,6,7,8,T1)

· continuation of posterior cord

· crosses lower border of posterior wall of axilla

· lies on tendon of latissimus dorsi

· gives 3 branches in axilla

· passes out through triangular space

· below lower border of teres major

· between long head of triceps and humerus