14 - Brachial Plexus

Question 1

What nerve roots does the brachial plexus contain, where does it start and terminate?

Answer 1

• Anterior rami of C5 to T1
• Starts in neck and terminates in axilla

Question 2

How is the brachial plexus divided into five parts?

Answer 2

• Roots
• Trunks
• Divisions
• Cords
• Branches

Question 3

What do the posterior rami of C5-T1 innervate?

Answer 3

The skin of the back and the muscles of the back

Question 4

How do the roots of the brachial plexus pass to where they converge to form trunks?

Answer 4

• Pass between anterior and middle scalene muscles to enter posterior triangle of neck
• At base of neck they form three trunks: superior, middle and inferior

Question 5

What nerve root does each trunk contain?

Answer 5

• Superior: C5 and C6
• Middle: C7
• Inferior: C8 and T1

Question 6

Where do the trunks of the brachial plexus go next and what do they combine to form?

Answer 6

• Posterior triangle of neck
• Form divisions, anterior and posterior, which leave posterior traingle and go into axilla

Question 7

Where do the divisions of the brachial plexus go and what do they form?

Answer 7

• From posterior triangle into the axilla where they form cords
• Named by position relative to axillary artery
• Lateral, posterior and medial

Question 8

What are each of the three cords made from?

Answer 8

- Lateral cord: anterior divisions of superior and middle trunks

- Posterior cord: Posteriors of all three trunks

- Medial cord: Continuation of inferior trunk

Question 9

How do the cords then form branches in the brachial plexus and what do they supply?

Answer 9

• Musculocutaneous, median and ulnar from anterior divisions supply the flexor muscles
• Axillary and radial from posterior divisions supply the posterior arm, the extensors

Question 10

How can you remember the spinal nerve roots for the 5 major brachial plexus branches?

Answer 10

Question 11

What is the common cause of injury of the upper brachial plexus?

Answer 11

• Excessive increase in angle between neck and shoulder, e.g trauma and birth
• C5 and C6 myotomes will be lost

Question 12

What muscles will be paralysed with an upper brachial plexus injury?

Answer 12

Any nerve with root C5 or C6

Question 13

What is the physical symptoms of an upper brachial plexus injury?

Answer 13

• Limb hanging by side in medial rotation, adducted arm and extented elbow

- Erb’s Palsy

Question 14

What is the typical mechanism of injury to the lower brachial plexus?

Answer 14

• Forced hyperextension or hyperabduction
  e. g falling from height and grabbing tree, pulling baby in delivery
• C8 and T1 affected so issues with those myotomes

Question 15

What muscles will be affected with a lower brachial plexus injury?

Answer 15

• Intrinsic muscles of hand, flexors of forearm supplied by ulnar nerve
• Muscles supplies by C8 and T1 within median and radial nerves

Question 16

What is the physical signs of lower brachial plexus injury?

Answer 16

- Klumpke’s palsy

- Claw hand: hyperextension of all metacarpophalangeal joints, flexion of interphalangeal, thumb abduction and wasting of interossei

Question 17

Label the following nerves on the brachial plexus.

Answer 17

Question 18

Label the following diagram.

Answer 18

Question 19

What are the contents of the axilla?

Answer 19

Question 20

What are the contents of the fibrous axillary sheath?

Answer 20

Axillary artery, axillary vein and cords & branches of the brachial plexus

Question 21

How can you remember the branches of the brachial plexus and the nerve roots that supply them?

Answer 21