Brachial plexus Flashcards
What is the course of the brachial plexus?
- originates in neck
- passes laterally and inferiorly over rib 1
- enters axilla
What makes up the roots of the brachial plexus?
ventral rami of spinal nerves C5-T1
How many trunks are there?
3: superior, middle, inferior
What makes up the superior trunk?
roots C5 and C6 joining
what makes up the middle trunk?
root of C7 alone
what makes up the inferior trunk?
roots of C8 and T1 joining
what are divisions made of?
each of the trunks have an anterior and posterior division
what do the 3 anterior divisions form?
forms part of the brachial plexus that ultimately give rise to peripheral nerves associated with anterior compartment of arm/forearm
what do the 3 post divisions combine to form?
form parts that give rise to nerves associated with posterior compartments
what are the cord positions described with respect to?
to the axillary artery
what makes up the posterior cord?
posterior divisions of all 3 trunks
contributions from C5-T1
posterior to second part of axillary artery
what makes up the lateral cord?
anterior divisions of superior and middle trunk
contributions from C5-C7
lateral to 2nd part of axillary artery
what makes up the medial cord?
anterior divisions of inferior trunk alone
contributions from C8-T11
medial to second part of axillary artery
where do the nerves associated with the anterior compartment come from?
medial and lateral cord
where do the nerves associated with the posterior compartment come from?
posterior cords
what are the major terminal branches of the brachial plexus?
- musculocutaneous nerve
- median nerve
- axillary nerve
- radial nerve
- ulnar nerve
what does the musculocutaneous nerve innervate?
- innervates all of anterior compartment of arm
- brachialis, biceps brachii, coracobrachialis
- branches off lateral cord
what does the median nerve innervate?
- most of the flexors of wrist
- thenar muscles
- formed by joining of medial and lateral cords
what does the axillary nerve innervate?
- deltoid and teres minor
- branches off posterior cord
what does the radial nerve innervate?
- all posterior arm and forearm
- some sensory innervation to hand
- terminal branch of posterior cord
what does the ulnar nerve innervate?
- some flexors (FCU, half of FDP)
- most of intrinsic muscles of hand
- terminal branch of medial cord
what are the branches off the roots?
- long thoracic nerve
- dorsal scapular nerve
what is the long thoracic nerve? what does it innervate?
- innervates serratus anterior
- contributed by C5, 6, 7 ventral rami directly
what is the dorsal scapular nerve? what does it innervate?
- branch of ventral rami of C5
- innervates rhomboids
what happens when there is damage to the dorsal scapular nerve?
patient unable to bring their inferior angle of the scapula together
what are the branches off the trunks?
- originate from superior trunk
- suprascapular nerve
- nerve to subclavius muscle
what is the suprascapular nerve? what does it innervate?
- direct branch of superior trunk
- innervates supraspinatus, infraspinatus, glenohumeral joint
what is the nerve to the subclavius? what does it innervate?
innervates subclavius
C5/6
what are the branches off the lateral cord? (not terminal branches)
lateral pectoral nerve
What is the lateral pectoral nerve?
- branch of lateral cord
- innervating pec major
what are the branches off the medial cord? (not terminal branches)
- medial pectoral nerve
- medial cutaneous nerve of arm
- medial cutaneous nerve of forearm
what is the medial pectoral nerve?
- branch of medial cord
- innervates pec minor
what is the medial cutaneous nerve of the arm?
- innervates upper part of medial surface of arm/ floor of axilla
what is the medial cutaneous nerve of forearm?
- innervates skin over medial surface of forearm down to wrist
what are the branches off the posterior cord? (not terminal branches)
- thoracodorsal nerve
- upper subscapular
- lower subscapular
what is the thoracodorsal nerve?
- branch of posterior cord
- innervating lattissimus dorsi
what is the upper subscapular nerve?
- branch of posterior cord
- innervating upper part of subscapularis
what is the lower subscapular nerve?
- branch of posterior cord
- innervating inferior portion of subscapularis and teres major
what are the shoulder girdle muscles innervated by? (motor innervation)
C5-7
what are the shoulder joint muscles and elbow flexors innervated by? (motor innervation)
C5, C6
what are the elbow extensors innervated by? (motor innervation)
C7-8
what provides the motor innervation to the wrist and coarse hand muscles?
C6-8
what provides the motor innervation to the small muscles of the hand?
C8-T1
how do you test the spinal nerve C5?
test sensation just anterior to elbow
how do you test the spinal nerve C6?
test sensation in tip of thumb
how do you test the spinal nerve C7?
test sensation in middle finger
how do you test the spinal nerve C8?
test sensation in little finger
how do you test the spinal nerve T1?
test sensation on medial aspect of upper arm
what are the branches of the radial nerve?
- posterior cutaneous nerve of arm + forearm
- inferior lateral cutaneous nerve of arm
- superficial branch
what does the radial nerve innervate?
- medial part of posterior upper arm
- posterior lateral part of forearm
- lateral part of lower arm + forearm
- lateral part of dorsal hand
- some sensation in thenar eminence
what does the ulnar nerve give innervation to?
- medial part of anterior arm below elbow
what does the dorsal cutaneous branch of the ulnar nerve give sensation to?
- small digit and half of ring finger on dorsal and palmar sides
what does the axillary nerve give innervation to?
- regimental patch
= lateral aspect of upper part of arm near shoulder joint
what forms the lateral cutaneous nerve?
given off by musculocutaneous nerve
what does the lateral cutaneous nerve supply?
- medial part of anterior aspect of lower 2/3rds of arm
- crosses over at elbow to supply lateral part of anterior distal 2/3rds of forearm
what happens when there is injury to the axillary nerve?
- unable to raise arms
- wasting of deltoid
what happens when there is injury to the radial nerve?
- can’t extend elbow joint or wrist joint
- loss of sensation of lateral part of arm/forearm
- wrist drop
- loss of power grip
what happens when there is injury to ulnar nerve?
- ulnar claw
- unable to adduct or abduct fingers
what happens when there is injury to median nerve?
- paraesthesia of lateral half of palmar side of hand
- muscle wasting of thenar muscles and thenar eminence
- hand of benediction (when try to flex fingers, only last 2 will flex)
what happens when there is injury to the long thoracic nerve?
- winging of scapula
what causes damage to the upper roots?
- hyperextension of spine/neck
- stretching of plexus by excessive pulling shoulder
what is damage to the upper roots known as?
Erb’s palsy
when there is damage to the upper roots, which nerves are affected?
- radial
- musculocutaneous
- median
- axillary
what happens when there is damage to the upper roots?
- arm drop, due to loss of deltoid
- pronation of hand, due to loss pf biceps
- flexion of hand, due to loss of extensor muscles of wrist
what causes damage to the lower roots?
- hyperabduction of shoulder due to gripping overhead to break fall
- pulling on arm of a child during childbirth
what is damage to the lower roots known as?
Kumpke’s palsy
when there is damage to the lower roots, which nerves are affected?
main issues on ulnar and median nerve
what happens when there is damage to the lower roots?
- loss of flexion of wrist
- loss of extension of last 2 digits
- limited hand movements
- loss of thumb movements
