BRACHIAL PLEXUS

Question 1

The brachial plexus is derived of which nerve roots?

Answer 1

C5 - T1

Question 2

Loss of ability to abduct arm from 15 to 90° and loss of sensation over the deltoid is caused by damage to which nerve? Which roots of the BP supply this nerve? Give two examples of injuries that will cause damage to this nerve

Answer 2

Axillary nerve C5, C6

• Proximal humerus fracture: elderly patient fall
• Dislocated shoulder: anterior displacement of humerus

Question 3

The radial nerve is responsible for which movement in the arm, wrist, fingers? Which part of the arm does it provide sensation to?

Answer 3

Movement: Extensors in arms, wrists, fingers → including triceps (elbow extension)

Sensation: back of hand/forearm

Question 4

This woman has been asked to extend both wrists. What is wrong with her left wrist?

Answer 4

Wrist drop: radial nerve lesion → wrist flexors will dominate

Question 5

What type of fracture is more likely to result in a radial nerve lesion?

Answer 5

Midshaft humeral fracture causing radial groove damage

Question 6

Which nerve innervates the biceps? What is the sensory component of this nerve?

Answer 6

Musculocutaneous nerve

→ Sensation to lateral forearm

Question 7

What are the two main trunk lesions of the brachial plexus?

Answer 7

• Upper (Superior): C5 to C6 → Erb’s palsy
• Lower (Inferior): C8 to T1 → Klumpke palsy

Question 8

What’s this baby’s deal?

what is this condition caused by? Explain which three nerves are involved

Answer 8

Erb’s palsy/upper plexus injury → caused by excessive angle at neck/shoulder, classically birth trauma

• Axillary: Normally abducts = shoulder flat at side
• Musculocutaneous: Normally flexes = forearm extended
• Suprascapular: Normally external rotation = will be internally rotated

Question 9

This person fell from a tree and clung onto branch on the way down. They presented with this hand, what have they damaged? Which nerves are affected?

Answer 9

Lower plexus injury/Klumpke palsy

• Ulnar and median nerve is affected
• Affects intrinsic hand muscles → hyperextended metacarpophalangeal joints and flexed interphalangeal joints = clawed hand

Question 10

What is thoracic outlet syndrome?

Answer 10

Compression of nerves and vessels leaving thorax through the thoracic outlet, a space between first rib and clavicle

Question 11

What is the anatomical location where nerves and blood vessels become compressed in thoracic outlet syndrome?

Answer 11

Scalene triangle: formed by →

• Anterior scalene
• Middle scalene
• First rib

Question 12

What anatomical variance predisposes to thoracic outlet syndrome?

Answer 12

Cervical rib

​→ these people are more likely to get thoracic outlet syndrome after hyperextension-flexion injury (whiplash)

Question 13

What part of the brachial plexus is normally injured in thoracic outlet syndrome? Which palsy will this cause? What symptoms are associated with vascular compression? Which movement typically worsens the symptoms?

Answer 13

Lower plexus injury: Klumpke palsy (claw hand)

• ​Venous compression: arm swelling
• Arterial compression: rare, Ischaemic hand (colder), lower blood pressure in that arm, weak distal pulses

► Symptoms typically worsened by raising the arm

Question 14

Which nerve is derived from C5, C6 and C7 and comes off of the brachial plexus before the development of trunks? Which muscle does it innervate? What are the movements of this muscle (arm and scapula)?

Answer 14

Long thoracic nerve

Serratus anterior muscle: abduction of arm above 90°, protraction of scapula

Question 15

What is this condition? What is it caused by?

Answer 15

Winging of scapula

Long thoracic nerve injury