Advanced Brachial Plexus Roots and Trunks Quiz

Q1. Why can traction that markedly separates the head from the shoulder preferentially injure the upper trunk?

• The upper trunk lies inside the subclavian vein
• The upper trunk contains only sympathetic fibers
• The C5-C6 upper trunk is vulnerable to excessive neck-shoulder separation
• The upper trunk is fixed to the thyroid gland

Q2. Which roots are most associated with a classic upper trunk brachial plexus lesion?

• C5-C6
• T1-T2 only
• C8-T1
• C7-C8

Q3. Why can forceful superior traction on the upper limb preferentially injure the lower trunk?

• The lower trunk passes through the carotid canal
• The lower trunk contains only motor fibers to the diaphragm
• The C8-T1 lower trunk is stretched by excessive superior limb traction
• The lower trunk is attached to the hyoid

Q4. Which roots are most associated with a classic lower trunk brachial plexus lesion?

• C6-C7
• C5-C6
• C8-T1
• C7 only

Q5. Why may a lower trunk lesion near the root of the neck be associated with Horner syndrome in some injuries?

• The lower trunk directly supplies the pupil
• The suprascapular nerve innervates the superior cervical ganglion
• The ulnar nerve carries parasympathetic fibers to the eye
• A proximal lesion may also damage nearby cervical sympathetic pathways

Q6. Why can injury to the long thoracic nerve occur at the root level before trunks are formed?

• It originates from the vagus nerve
• It arises only from the lower trunk
• It is a terminal branch of the medial cord
• It arises directly from C5-C7 roots

Q7. Why is the interscalene interval clinically important for regional anesthesia?

• The plexus runs inside the carotid sheath
• Roots and proximal trunks are accessible between anterior and middle scalene
• The brachial plexus is superficial to platysma
• All terminal nerves lie within sternocleidomastoid

Q8. Why can an interscalene brachial plexus block affect the phrenic nerve?

• The phrenic nerve is a branch of the upper trunk
• The phrenic nerve passes through middle scalene with C8
• The phrenic nerve travels inside the lower trunk
• The phrenic nerve lies close by on anterior scalene

Q9. How does the first rib help define the transition from trunks to divisions?

• The trunks divide near the lateral border of the first rib
• All roots terminate at the medial first rib
• The cords form medial to the scalene tubercle
• The first rib separates C5 from C6

Q10. Which statement best integrates the anatomy of brachial plexus roots and trunks?

• T1-T5 roots form trunks anterior to anterior scalene with the subclavian vein
• The brachial plexus begins as terminal nerves at the clavicle
• C5-T1 roots organize into three trunks in the interscalene and supraclavicular regions before dividing near the first rib
• C1-C4 roots form three trunks inside the carotid sheath