Brachial plexus

Question 1

From which spinal nerves does it originate?

Answer 1

Ventral rami of C5 to Th1

Question 2

How are the parts of the plexus divided?

Answer 2

Roots, Trunks, Divisions, Cords, Branches

Mnemonic: Really Tired? Drink Coffee.

Roots - between anterior and medial scalene muscles

Trunks - above clavicle

Divisions - behind clavicle

Cords - in axilla

Question 3

What are clinical examples of the brachial plexus?

Answer 3

Scalene syndrome:

• Additional cervical rib compresses plexus brachialis and subclavian artery in scalele gap (between anterior and median scalene).

Costoclavicular syndrome:

• Compression by low clavicle

Palsies:

• Radial nerve = wrist drop
• Ulnar nerve = pledge hand
• Axillary nerve = no abduction
• Musculocutaneous nerve = no flexion

Question 4

What nerve make up the brachial plexus, and what muscles do they innervate?

Answer 4

Musculocutaneous nerve:

All muscles in the anterior compartment of the arm.

Axillary nerve:

Deltoid and teres minor.

Median nerve:

Muscles in the anterior part of the forearm.

EXCEPT the flexor carpi ulnaris (ulnar nerve) and the flexor digitorum profundus (medial half from ulnar nerve).

Thenar muscles in hand.

Ulnar nerve:

All hand muscles

EXCEPT lateral two lumbricals (median nerve) and the thenar muscles (median nerve).

Flexor carpi ulnaris and medial half of flexor digitorum profundus.

Radial nerve:

All muscles in the posterior part of the arm and forearm.