Brachial Plexus

Question 1

Where does the brachial plexus originate?

Answer 1

Ventral primary rami of C5-T1

Question 2

How many roots of the brachial plexus are there initially? How many trunks do these form?

Answer 2

5 roots, these will combine to form 3 trunks

Question 3

The 5 roots of the brachial plexus combine to form what 3 trunks?

Answer 3

Upper trunk = C5 + C6

Middle trunk = Continuation of C7

Lower trunk = C8 + T1

Question 4

The 5 roots of the brachial plexus combine to form 3 trunks: upper, middle, and lower. These trunks split to form how many total divisions?

Answer 4

6 divisions (an anterior and posterior division per trunk)

Question 5

The 5 roots of the brachial plexus combine to form 3 trunks: upper, middle, and lower. These trunks split to form 6 total divisions. These divisions combine to form ___ cords which surround the _________ artery, and they are named for their relationship with this artery

Answer 5

3; axillary

Question 6

The 5 roots of the brachial plexus combine to form 3 trunks: upper, middle, and lower. These trunks split to form 6 total divisions. These divisions combine to form 3 cords which surround the axillary artery.

What makes up the 3 cords?

Answer 6

Lateral cord (C5-7) = anterior division of upper trunk + anterior division of middle trunk

Medial cord (C8-T1) = continuation of anterior division of lower trunk

Posterior cord (C5-T1) = posterior divisions of all 3 trunks

Question 7

The 5 roots of the brachial plexus combine to form 3 trunks: upper, middle, and lower. These trunks split to form 6 total divisions. These divisions combine to form 3 cords: the lateral cord (C5-7), the medial cord (C8-T1), and the posterior cord (C5-T1). Each cord has branches that supply motor and sensory innervation to the upper extremity.

What are the 3 branches of the lateral cord? Which of these are terminal branches?

Answer 7

Lateral pectoral n. (C5-7)

Musculocutaneous n. (C5-7) = TERMINAL

Lateral root of median n.

Question 8

The 5 roots of the brachial plexus combine to form 3 trunks: upper, middle, and lower. These trunks split to form 6 total divisions. These divisions combine to form 3 cords: the lateral cord (C5-7), the medial cord (C8-T1), and the posterior cord (C5-T1). Each cord has branches that supply motor and sensory innervation to the upper extremity.

What are the 5 branches of the medial cord? Which of these are terminal branches?

Answer 8

Medial pectoral n. (C8-T1)

Medial brachial cutaneous n. (C8-T1)

Medial antebrachial cutaneous n. (C8-T1)

Ulnar n. (C8-T1) = TERMINAL

Medial root of median n.

Question 9

The 5 roots of the brachial plexus combine to form 3 trunks: upper, middle, and lower. These trunks split to form 6 total divisions. These divisions combine to form 3 cords: the lateral cord (C5-7), the medial cord (C8-T1), and the posterior cord (C5-T1). Each cord has branches that supply motor and sensory innervation to the upper extremity.

What are the 5 branches of the posterior cord? Which of these are terminal branches?

Answer 9

Upper subscapular n. (C5-6)

Thoracodorsal n. (C6-8)

Lower subscapular n. (C5-6)

Axillary n. (C5-6) = TERMINAL

Radial n. (C5-T1) = TERMINAL

Question 10

What branches of the brachial plexus form the median n.?

Answer 10

Lateral root of median n. (branch of lateral cord)

Medial root of median n. (branch of medial cord)

Question 11

What are some examples of syndromes resulting from brachial plexus injury?

Answer 11

Erb’s Palsy (Erb-Duchenne paralysis)

Klumpke-Dejerine paralysis

Thoracic Outlet Syndrome

Question 12

What part of the brachial plexus is affected by Erb’s palsy? What part of the body does this affect?

Answer 12

Upper part, especially C5-6

Affects the shoulder and arm

Question 13

Erb’s Palsy affects the shoulder and arm due to damage in the upper part of the brachial plexus. What are some mechanisms of injury that cause Erb’s Palsy?

Answer 13

Excessive separation of the arm and shoulder (such as with motorcycle accidents or athletic injuries)

Question 14

How does excessive separation of the arm and shoulder lead to Erb’s Palsy?

Answer 14

Dorsal and ventral nerve roots are pulled out of the spinal cord from C5-6

Question 15

Excessive separation of the arm and shoulder lead to Erb’s Palsy due to dorsal and ventral nerve roots being pulled from the spinal cord from C5-6. What muscles are paralyzed?

Answer 15

Deltoid m.
Supraspinatus m.
Infraspinatus m.
Teres minor m.
Subscapularis m.

Flexors of the elbow are also weakened

Question 16

Paralysis of the deltoid, supraspinatus, infraspinatus, teres minor, and subscapularis mm. in addition to weakness of the elbow flexors would result in what symptoms in Erb’s Palsy patients?

Answer 16

Adduction and medial rotation of arm

Extension of elbow

Flexion of hand

Loss of sensation in C5-6 dermatomes supplied by dorsal and ventral primary rami (skin of back and lateral surface of upper extremity)

Question 17

What part of the brachial plexus is affected by Klumpke-Dejerine paralysis? What part of the body does this affect?

Answer 17

Lower part of plexus, especially C8-T1

Affects the forearm and hand

Question 18

Klumpke-Dejerine paralysis involves the lower part of the brachial plexus, especially C8-T1 and affects the forearm and hand. What are some mechanisms of injury that may lead to this type of paralysis?

Answer 18

Upper extremity being suddenly pulled upward (may occur with forceful pulling of infant’s shoulder during delivery or grasping something above you to break a fall)

Question 19

Klumpke-dejerine paralysis may result from forceful pull of an infant’s shoulder during delivery. What effect would this have on that limb during development?

Answer 19

The affected limb will not grow to the same size as the unaffected extremity

Question 20

Klumpke-Dejerine paralysis typically results in paralysis of what major nerve? What movements/sensations are affected?

Answer 20

Ulnar n.

Impairment of wrist flexion and movements of intrinsic mm. of the hand

Reduced sensation along the medial side of the arm, forearm, and hand

Question 21

Thoracic Outlet Syndrome results from chronic injury to the brachial plexus in what region of the neck?

Answer 21

Lower part of neck, so lower part of brachial plexus is affected - at or close to the level where it crosses the 1st rib (apex of the axilla)

Question 22

Thoracic Outlet Syndrome affects the brachial plexus at the axis of the axilla. It also commonly involves injury to what artery?

Answer 22

Subclavian a.

Question 23

What are the symptoms of thoracic outlet syndrome?

Answer 23

Pain in fingers, hand, forearm, arm, and shoulder

Paresthesia perceived in dermatomes C8-T1