brachial plexus

Question 1

Which spinal nerves make the Brachial plexus, and differentiate between prefixed and postfixed plexus.

Answer 1

Brachial plexus is formed by the anterior rami of the lower four cervical and the first thoracic (C5,6,7,8 and T1) spinal nerve with little contribution from C4 and T2.

In a prefixed plexus, the contribution by C4 is large and C5 is present. T1 is small and T2 is absent. Think, upward shifting.

In a postfixed plexus, the T1 is large, T2 is always present, C4 is absent, and C5 is reduced in size. Think, downward shifting.

Question 2

Describe the components of the brachial plexus

Answer 2

1. Roots (5)
   - Five roots constituting of the anterior primary rami of C5 to T1 nerves.
   - Located in the neck deep to the scalenous anterior muscle
2. Trunk (3)
   - C5 and C6 roots join to form the upper trunk.
   - C7 root alone in the middle trunks
   - C8 and T1 form the lower trunk
   - Located in the neck occupying the cleft between scalenus medius behind, and the scalenus anterior in front.
3. Divisions (x2)
   - Each trunk has an anterior and posterior division
   - Located behind the clavicle
4. Cords (3)
   - Lateral cord from Anterior divisions of the upper and middle trunks uniting.
   - Medial cord from Anterior division of the lower trunk only.
   - Posterior cord from the posterior divisions of the three trunks.

Question 3

Describe the Branches from Roots

Answer 3

1. Long thoracic nerve / nerve to serratus anterior (C5, C6, C7)
2. Dorsal scapular nerve / nerve to rhomboisd (C5)
3. Scalene muscles and longus colli (C5,6,7,8) and there is contribution to phrenic nerve (C5).

Question 4

Describe the Branches from Roots

Answer 4

1. Long thoracic nerve / nerve to serratus anterior (C5, C6, C7)
2. Dorsal scapular nerve / nerve to rhomboisd (C5)
3. Scalene muscles and longus colli (C5,6,7,8) and there is contribution to phrenic nerve (C5).

Question 5

Describe the branches from trunks

Answer 5

1. Suprascapular nerve (C5, C6)
2. Nerve to subclavius (C5, C6)

The branches arising from roots and trunks are supraclavicular branches of the brachial plexus.

Question 6

Describe the Clinical Aspects of the Brachial Plexus in relation to Erb’s Point

Answer 6

The Erb’s Point
- Region of upper trunk of brachial plexus where the six nerves meet. 5th and 6th cervical roots join to form the upper trunk, which gives the suprascapular and subclavius nerves. and also divides into anterior and posterior

Can result in Erb’s Paralysis:
1. Nerves involved are C5 and C6
2. Paralyzes deltoid, supraspinatus infraspinatus, biceps brachii, brachialis, brachioradialis, supinator, extensor carpi radialis longus
3. Policeman’s tip / Waiter’s tip position of hands.
4. Sensory loss of the outer aspect of the arm
5. Autonomic signs are absent.

Can also result in Klumpke’s paralysis
1. Nerves involved are C8 and T1.
2. All intrinsic muscles of hand are affected.
3. Results in ulnar claw hand
4. ALong the medial border of forearm and hand.
5. Autonomic signs are presetn (Horner’s syndrome)

Question 7

Describe the Clinical Aspects of brachial plexus in relation to the Brachial Plexus Blcok

Answer 7

B.P.B is a method of anesthesia for surgery on upper limb (repair of complicated wounds of hand).

Brachial Plexus in the subclavian triangle is accessible via the supraclavicular and infraclavicular (axillary).

Insert need just above the midpoint of clavicle, lateral to the pulsation of subclavian artery

Question 8

Describe the Clinical Aspects of brachial plexus in relation to Surgical approach to Axilla

Answer 8

The axilla is approached surgically through the skin of the floor of axilla for the excision of axillary lymph nodes to treat the cancer of the breast.

Structures at risk are, intercostobrachial nerve, long thoracic nerve, and thoraco-dorsal nerve/artery.

Question 9

Describe the branches of the Medial Cord

Answer 9

1. Medial Root of Median Nerve
2. Medial Pectoral Nerve
3. Medial Cutaneous Nerve of arm
4. Medial cutaneous nerve of forearm
5. Ulnar Nerve