Brachial Plexus – Quiz

📝 Practice MCQs

Welcome to your Upper Limb – Chapter 5 – Brachial Plexus

A newborn delivered after difficult labor presents with an adducted, medially rotated arm and an extended, pronated forearm. The lesion most likely involves:

Medial cord

Lower trunk (C8–T1)

Posterior cord

Upper trunk (C5–C6)

None

A variation in the formation of the brachial plexus includes contribution from the ventral ramus of C4. This variation is termed:

Postfixed brachial plexus

Prefixed brachial plexus

Cervicothoracic plexus

Accessory brachial plexus

None

The posterior cord of the brachial plexus is formed by the union of:

Posterior divisions of all three trunks

Anterior divisions of upper and middle trunks

Anterior division of lower trunk only

Posterior divisions of upper and middle trunks only

None

The thickest branch of the brachial plexus and direct continuation of the posterior cord is:

Axillary nerve

Radial nerve

Ulnar nerve

Musculocutaneous nerve

None

During dissection, a Y-shaped neural configuration is observed anterior to the third part of the axillary artery. This structure represents:

Formation of musculocutaneous nerve

Division of radial nerve

Formation of ulnar nerve

Union of roots forming median nerve

None

Which nerve passes through the suprascapular notch deep to the superior transverse scapular ligament and supplies both supraspinatus and infraspinatus?

Nerve to subclavius

Dorsal scapular nerve

Suprascapular nerve

Axillary nerve

None

During neck surgery, a nerve trunk emerging between scalenus anterior and scalenus medius is identified as continuing directly from the C7 ventral ramus without joining another root. Which trunk is this?

Lower trunk

Posterior cord

Upper trunk

Middle trunk

None

A nerve arising from C5–C7 roots courses on the superficial aspect of serratus anterior in the midaxillary line. Injury to this nerve is most likely to produce:

Winging of the scapula

Inability to abduct the shoulder

Wrist drop

Loss of elbow flexion

None

A patient who falls on an outstretched hand develops clawing of fingers along with ptosis, miosis, and anhidrosis. Which roots are primarily affected?

C8 and T1

C7 and C8

C6 and C7

C5 and C6

None

In an infraclavicular brachial plexus block, the anesthetist places the needle around structures arranged around the second part of the axillary artery. Which cord lies medial to the artery?

Upper trunk

Posterior cord

Medial cord

Lateral cord

None

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🎙️ Frequently Asked Viva Questions

Q1. Why are the cords of the brachial plexus named lateral, medial, and posterior?
Answer: They are named according to their relationship to the second part of the axillary artery.

Q2. Why is the upper trunk the most common site of brachial plexus injury?
Answer: It is stretched by excessive separation of the head and shoulder, commonly during difficult childbirth or falls.

Q3. What is the anatomical importance of Erb’s point?
Answer: It is the junction where six structures meet, making it the commonest site of upper trunk (C5–C6) injury.

Q4. Why does Erb’s palsy produce the “waiter’s tip” deformity?
Answer: Paralysis of abductors, lateral rotators, elbow flexors, and supinators leaves the arm adducted, medially rotated, extended, and pronated.

Q5. Why is forearm pronation seen in Erb’s palsy?
Answer: Paralysis of the biceps brachii abolishes supination, leaving the pronator muscles unopposed.

Q6. Why is claw hand the characteristic deformity in Klumpke’s paralysis?
Answer: Paralysis of the lumbricals and interossei causes MCP hyperextension and IP flexion due to unopposed long flexors and extensors.

Q7. Why may Horner syndrome occur in Klumpke’s paralysis?
Answer: Injury to the T1 root damages sympathetic fibers ascending to the head and neck.

Q8. Why does a cervical rib produce neurological symptoms in the upper limb?
Answer: It compresses the T1 nerve root or lower trunk of the brachial plexus, causing sensory and motor deficits.

Q9. Why is the long thoracic nerve especially vulnerable during axillary surgery?
Answer: It runs superficially on the serratus anterior along the midaxillary line and is easily injured during lymph node dissection.

Q10. What is the anatomical basis of winging of the scapula following long thoracic nerve injury?
Answer: Paralysis of the serratus anterior prevents fixation of the scapula against the thoracic wall.

Q11. Why does the median nerve contain fibers from all five roots (C5–T1)?
Answer: It is formed by the union of lateral (C5–C7) and medial (C8–T1) roots.

Q12. Why is ultrasound guidance preferred for brachial plexus block?
Answer: It improves accuracy of anesthetic placement while reducing injury to adjacent nerves and blood vessels.