Anatomy

Composition

 

C5 - T1

- prefixed: C4 (more common)

- post fixed: T2

 

Roots (3 Branches / LSD)(Interscalene)

Trunks (1 Branch)(Posterior Triangle)

Division (Clavicle)

Cords (5,5,3)(Axillary Artery)

 

Nerve roots

 

Formed by ventral and dorsal nerve rootlets

- in foramen

- DRG has cell bodies of sensory nerves

- rupture proximal to DRG indicates preganglionic

 

Run between scalenius anterior and medius

 

Branches

- long thoracic nerve (C5/6/7)(serratus anterior)

- nerve to subclavius (C5/6)

- dorsal scapula nerve (C5)(rhomboids)

 

T1 sympathetic ganglion close to T1 nerve root

- frequently injured together

 

Trunks

 

A.  Upper 

- C 5/6

- merger is Erb's point

- where SSN exits

- injury: SSN, axillary, MCN (lose SS, IS, deltoid, biceps)

 

B.  Middle

- C7

 

C.  Lower

- C8/T1

 

Branches

- suprascapular nerve (C5,6) from upper trunk

 

Divisions

 

Trunks divide into anterior and posterior

- behind clavicle

 

Cords

 

A.  Posterior cord (5)

- all three posterior divisions

- C5 - T1

- posterior to axillary artery

 

Branches

- radial is terminal branch

- axillary

- upper and lower subscapular

- thoracodorsal

 

B.  Lateral cord (3)

- anterior divisions of upper and middle trunk

- C5/6/7

- lateral to axillary artery

 

Branches

- MCN lateral to artery

- lateral branch of median nerve / runs across artery

- lateral pectoral

 

C.  Medial cord (5)

- anterior division of lower trunk

- C8 / T1

- medial to axillary artery

 

Branches

- medial median

- medial pectoral

- MCNA, MCNFA (medial cutaneous nerve of arm and forearm)

- ulna nerve is terminal branch (runs medial to artery)

 

Sensation

 

Roots / ASIA

 

Peripheral nerves

 

Supraclavicular region  C4

 

Regimental patch C5

- axillary nerve

 

Radial forearm C6

- LCNFA / MCN

 

Dorsal first web space C6

- radial nerve

 

Thumb and thenar eminence C6

- median nerve

 

Middle finger C7

- median nerve

 

Little finger C8

- ulnar nerve

 

Ulnar forearm T1

- MCNFA

 

Medial arm T2

- MCNA

 

Motor

 

Nerve roots / ASIA

 

C5 / deltoid / bicep

C6 / wrist extensors

C7 / tricep

C8 / MF FDP

T1 / interossei

 

Adjacent nerves

 

Trapezius (CN Xl)

- patient shrugs shoulders against resistance

 

Branches from roots

 

Rhomboid (C5)

- dorsal scapular nerve

- patient retracts scapula

- examiner uses hand to palpate

 

Serratus anterior (C567)

- long thoracic nerve

 

A.  Patient pushes against wall

- observe for winging

- patient protracts shoulder against resistance 

 

B. Some pateints won't be able to get arm up to wall

- raise arm for them

- get them to push arm away

 

Branches from the trunks

 

Supraspinatus (C5)

- suprascapular neve

- patient tries to initiate abduction of the arm from the side

 

Infraspinatus (C5)

- suprascapular nerve

- patient tries to externally rotate shoulder with arm by side

 

Branches of the posterior cord (C5-T1)

 

Deltoid (C5)

- axillary nerve

- patient abducts arm against resistance

 

Latissimus Dorsi (C7)

- thoracodorsal nerve

- patient adducts horizonal arm against resistance

 

Subscapularis

- upper and lower subscapular

 

Radial nerve

 

1.  Triceps (C78)

- patient extends elbow against resistance

 

2.  Brachioradialis (C6)

- patient flexes the elbow with forearm pronated

 

3.  ECRL (C67)

- radial nerve

- extend IF against resistance

 

4.  ECRB (C67)

- PIN

- extend MF

 

5. Wrist extension (C67-ECR, C67-ECU)

- radial and posterior interosseous nerve

- patient extends wrist

 

5.  Supinator (C6)

- patient supinates forearm in extension

 

6.  EDC (C8)

- PIN

- patient extends MCPJ

 

7.  ECU (C67)

- PIN

- extend wrist

 

8.  Extensor pollicis longus (C7)

- PIN

- patient extends thumb IPJ against resistance

 

Branches of the lateral cord (C5,6,7)

 

Pectoralis major (clavicular fibres) (C6)

- lateral pectoral nerve

- patient pushes arm forwards with arm horizontal

 

Biceps (C56)

- musculocutaneous nerve

- patient tries to flex elbow with forearm supinated

 

Lateral median nerve

 

1.  PT (C6)

- pronate in flexion

 

2.  FCR (C6)

- wrist extension

 

Branches of the medial cord (C8 / T1)

 

Pectoralis major (sternocostal fibres) (C7,8)

- medial pectoral nerve

- patient places hand on hip and pushes in

 

Medial branch median nerve

 

Flexor digitorum profundus (C8)

- AIN

- patient makes fist and resists extension of index finger

 

Flexor pollicis longus (C8)

- AIN

- patient flexes distal phalanx of thumb against resistance

 

Abductor pollicis brevis (TI)

- patient abducts thumb at right angles to palm against resistance

 

Ulna nerve

 

Flexor carpi ulnaris (C8)

- patient flexes wrist against resistance

 

Flexor digitorum profundus (C8)

- patient makes fist and resists extension of little finger

 

Interossei (TI)