Upper Limb — MCQs

Upper Limb Indian Medical PG Practice Questions and MCQs

Question 71: Which of the following statements regarding the brachial plexus is true?

A. A cervical rib typically involves the lateral cord.
B. The musculocutaneous nerve originates from the medial cord.
C. The radial nerve arises from the posterior cord. (Correct Answer)
D. A post-fixed brachial plexus is formed by C4, C5, C6, C7, C8, and T1.

Explanation: ### **Explanation** The brachial plexus is a network of nerves (C5-T1) providing motor and sensory innervation to the upper limb. Understanding its cords and branches is high-yield for NEET-PG. **1. Why Option C is Correct:** The **Posterior Cord** is formed by the union of the posterior divisions of all three trunks (Upper, Middle, and Lower). Its branches can be remembered by the mnemonic **ULTRA**: **U**pper subscapular, **L**ower subscapular, **T**horacodorsal, **R**adial, and **A**xillary nerves. The radial nerve (C5-T1) is the largest branch of this cord. The thoracodorsal nerve, a branch of the posterior cord, specifically crosses the axilla to the medial surface of the latissimus dorsi [1]. **2. Analysis of Incorrect Options:** * **Option A:** A **cervical rib** (an accessory rib from C7) typically compresses the **lower trunk** (C8, T1) or the **medial cord**, not the lateral cord. This leads to Thoracic Outlet Syndrome (TOS), where the brachial plexus is compressed as it passes through regions like the interscalene triangle or subcoracoid area, manifesting as neurogenic symptoms in over 90% of cases [2]. * **Option B:** The **musculocutaneous nerve** originates from the **lateral cord** (C5-C7). The medial cord gives rise to the ulnar nerve and the medial head of the median nerve. * **Option D:** A **post-fixed plexus** occurs when the plexus is shifted inferiorly, receiving a large contribution from **T2** and lacking C4. The roots involved are typically **C6 to T2**. A pre-fixed plexus involves C4 to C8. ### **High-Yield Clinical Pearls for NEET-PG:** * **Erb’s Palsy:** Injury to the Upper Trunk (C5, C6) resulting in "Policeman’s tip" hand. * **Klumpke’s Palsy:** Injury to the Lower Trunk (C8, T1) resulting in a "Claw hand." * **Winged Scapula:** Caused by injury to the **Long Thoracic Nerve** (Roots: C5, C6, C7), often during radical mastectomy. * **Radial Nerve Injury:** Commonly occurs at the **spiral groove** of the humerus, leading to **wrist drop**.

Question 72: Which of the following is NOT a ligament of the shoulder joint?

A. Coracoclavicular (Correct Answer)
B. Glenohumoral
C. Coracohumeral
D. Transverse humeral

Explanation: The shoulder joint (glenohumeral joint) is a ball-and-socket synovial joint characterized by a wide range of motion but inherent instability. Its stability is maintained by a series of intrinsic and extrinsic ligaments. **Why Coracoclavicular is the Correct Answer:** The **Coracoclavicular ligament** is not a ligament of the shoulder joint; rather, it is the primary stabilizer of the **Acromioclavicular (AC) joint**. It connects the coracoid process of the scapula to the undersurface of the clavicle and consists of two parts: the **conoid** and **trapezoid** ligaments. While it helps suspend the weight of the upper limb from the clavicle, it does not involve the humerus or the glenohumeral articulation. **Analysis of Incorrect Options:** * **Glenohumeral ligaments:** These are three thickenings (superior, middle, and inferior) of the anterior joint capsule that strengthen the shoulder joint. * **Coracohumeral ligament:** A strong band extending from the root of the coracoid process to the greater tubercle of the humerus, strengthening the upper part of the capsule. * **Transverse humeral ligament:** A small band bridging the gap between the greater and lesser tubercles, converting the bicipital groove into a canal for the long head of the biceps tendon. **High-Yield Clinical Pearls for NEET-PG:** * **Stability:** The shoulder joint is the most frequently dislocated joint in the body. * **Rotator Cuff (SITS):** The "dynamic stabilizers" of the shoulder are the Supraspinatus, Infraspinatus, Teres minor, and Subscapularis. * **Glenoid Labrum:** A fibrocartilaginous rim that deepens the glenoid cavity to increase stability. * **AC Joint Dislocation:** Often involves tearing of the coracoclavicular ligament, leading to the "step-off" deformity of the shoulder.

Question 73: Injury to the median nerve occurs frequently when which artery is used for taking an ABG sample?

A. Radial artery
B. Brachial artery (Correct Answer)
C. External carotid artery
D. Femoral artery

Explanation: ### Explanation **1. Why the Brachial Artery is Correct:** The **median nerve** and the **brachial artery** share a very close anatomical relationship in the cubital fossa. At the level of the elbow, the median nerve lies immediately **medial** to the brachial artery. Both structures are protected only by the thin bicipital aponeurosis. During an Arterial Blood Gas (ABG) sampling or a brachial artery puncture, a needle that deviates medially or is inserted too deeply can easily transfix or compress the median nerve, leading to sensory loss in the lateral 3.5 fingers and motor deficits in the forearm and hand. **2. Analysis of Incorrect Options:** * **A. Radial Artery:** This is the most common site for ABG sampling. While the superficial branch of the radial nerve is nearby, the median nerve is distant from the radial artery at the wrist. * **C. External Carotid Artery:** This artery is located in the neck. It is not used for routine ABG sampling, and its injury would involve cranial nerves (like the hypoglossal or vagus), not the median nerve. * **D. Femoral Artery:** Located in the femoral triangle in the groin. The nerve in close proximity here is the **femoral nerve** (lateral to the artery), not the median nerve. **3. NEET-PG High-Yield Pearls:** * **Cubital Fossa Contents (Medial to Lateral):** **M**edian Nerve, **B**rachial Artery, **B**iceps Tendon, **R**adial Nerve (Mnemonic: **MBBR**). * **Supracondylar Fracture of Humerus:** This is the most common traumatic cause of concurrent injury to the brachial artery and median nerve. * **Pronator Teres Syndrome:** Another site of median nerve entrapment, occurring as the nerve passes between the two heads of the pronator teres muscle. * **Allen’s Test:** Always performed before radial artery puncture to ensure collateral circulation via the ulnar artery.

Question 74: Which of the following arteries is most likely at risk during venipuncture at the cubital fossa?

A. Brachial (Correct Answer)
B. Common interosseous
C. Ulnar
D. Anterior interosseous

Explanation: **Explanation:** The **cubital fossa** is a common site for venipuncture, specifically targeting the **median cubital vein**. The correct answer is the **brachial artery** because of its critical anatomical relationship to this vein. 1. **Why Brachial Artery is Correct:** The brachial artery lies immediately deep to the median cubital vein. It is separated from the vein only by the **bicipital aponeurosis** (a thin, fibrous sheet). During venipuncture, if the needle passes too deeply or pierces the aponeurosis, it can inadvertently puncture the brachial artery, leading to hematoma or intra-arterial injection. 2. **Why Incorrect Options are Wrong:** * **Common Interosseous Artery:** This is a short branch of the ulnar artery that arises distal to the cubital fossa, deep in the forearm. * **Ulnar Artery:** While it originates in the cubital fossa as a terminal branch of the brachial artery, it quickly passes deep to the pronator teres muscle, moving away from the superficial venous access site. * **Anterior Interosseous Artery:** This is a branch of the common interosseous artery located deep on the interosseous membrane, far from the superficial cubital skin. **Clinical Pearls for NEET-PG:** * **Mnemonic for Cubital Fossa Contents (Medial to Lateral):** **MBBR** — **M**edian nerve, **B**rachial artery, **B**iceps tendon, **R**adial nerve. * **Bicipital Aponeurosis:** Also known as the "grace d'ieu" fascia, it serves as a protective barrier for the brachial artery and median nerve during venipuncture. * **Median Nerve:** Along with the brachial artery, the median nerve is also at risk of injury during deep needle insertion in the medial aspect of the fossa.

Question 75: The finer movements of the hand are controlled by which nerve?

A. Ulnar nerve (Correct Answer)
B. Median nerve
C. Radial nerve
D. Anterior interosseous nerve

Explanation: The **ulnar nerve** is known as the **"Musician’s Nerve"** because it controls the fine, intricate movements of the fingers. This is primarily due to its innervation of the majority of the intrinsic muscles of the hand, specifically the **interossei** (palmar and dorsal) and the **medial two lumbricals** [1]. These muscles are responsible for complex tasks such as finger abduction/adduction and the precise coordination required for playing instruments or typing. ### Why the other options are incorrect: * **Median Nerve:** Known as the "Laborer’s Nerve," it controls coarse movements and power grip [1]. While it supplies the thenar muscles (crucial for opposition), it does not control the majority of the muscles responsible for fine digital dexterity. * **Radial Nerve:** This is primarily an extensor nerve. In the hand, it provides only sensory innervation (to the dorsum). It does not supply any intrinsic hand muscles; its motor function is limited to the forearm for wrist and finger extension [1]. * **Anterior Interosseous Nerve (AIN):** A branch of the median nerve, it supplies the deep flexors of the forearm (Flexor Pollicis Longus, lateral half of Flexor Digitorum Profundus, and Pronator Quadratus). It is responsible for the "OK sign" but not fine digital coordination. ### High-Yield Clinical Pearls for NEET-PG: * **Ulnar Paradox:** The higher the lesion (at the elbow), the less prominent the clawing (because the FDP is paralyzed). * **Froment’s Sign:** Tests for ulnar nerve palsy; the patient compensates for adductor pollicis weakness by flexing the thumb (using the median-innervated FPL). * **Point of Compression:** Most common site is the **Cubital Tunnel** (elbow) or **Guyon’s Canal** (wrist).

Question 76: In ulnar nerve injury in the arm, all of the following are seen except?

A. Hypothenar atrophy
B. Adduction of thumb (Correct Answer)
C. Loss of sensation of the medial one-third of the hand
D. Claw hand

Explanation: In ulnar nerve injury, the characteristic clinical presentation results from the paralysis of the intrinsic muscles of the hand and the sensory loss in its distribution. [1] **Explanation of the Correct Answer:** **Option B (Adduction of thumb)** is the correct answer because it is **lost**, not seen, in ulnar nerve injury. The **Adductor Pollicis** is the only muscle in the thenar area supplied by the deep branch of the ulnar nerve. When the ulnar nerve is injured, the patient cannot adduct the thumb [1]. Instead, they compensate by flexing the thumb at the interphalangeal joint using the Flexor Pollicis Longus (median nerve), a clinical sign known as **Froment’s Sign**. **Analysis of Incorrect Options:** * **A. Hypothenar atrophy:** The ulnar nerve supplies all hypothenar muscles (Abductor, Flexor, and Opponens digiti minimi). Denervation leads to visible wasting of the hypothenar eminence. * **C. Loss of sensation of the medial one-third:** The ulnar nerve provides sensory innervation to the medial 1½ fingers and the corresponding medial third of the palm and dorsum of the hand. * **D. Claw hand:** This occurs due to paralysis of the medial two lumbricals and all interossei [1]. This leads to hyperextension at the MCP joints (unopposed Extensor Digitorum) and flexion at the IP joints (unopposed FDP), most prominent in the ring and little fingers. **High-Yield Clinical Pearls for NEET-PG:** * **Ulnar Paradox:** A high lesion (at the elbow/arm) results in a *less* severe claw hand than a low lesion (at the wrist) because, in high lesions, the Flexor Digitorum Profundus is also paralyzed, reducing the flexion of the IP joints. * **Muscles spared:** All thenar muscles except Adductor Pollicis are supplied by the Median nerve [1]. * **Point of injury:** In the arm, the ulnar nerve is most commonly injured due to fractures of the medial epicondyle of the humerus.

Question 77: Which of the following is NOT a branch of the brachial artery?

A. Profunda brachii
B. Superior ulnar collateral
C. Inferior ulnar collateral
D. Radial collateral (Correct Answer)

Explanation: The **brachial artery** is the direct continuation of the axillary artery, beginning at the lower border of the teres major muscle and ending at the level of the neck of the radius. ### Why "Radial Collateral" is the Correct Answer The **radial collateral artery** is not a direct branch of the brachial artery. Instead, it is one of the two terminal branches of the **profunda brachii artery** (the other being the middle collateral artery). It descends in the lateral intermuscular septum to participate in the anastomosis around the elbow joint. ### Analysis of Incorrect Options * **A. Profunda brachii:** This is the first and largest branch of the brachial artery. it arises just below the teres major and travels with the radial nerve in the spiral groove. * **B. Superior ulnar collateral:** Arises from the middle of the arm and accompanies the ulnar nerve behind the medial epicondyle. * **C. Inferior ulnar collateral:** Arises about 5 cm above the elbow and passes anterior to the medial epicondyle. ### NEET-PG High-Yield Facts * **Termination:** The brachial artery terminates by dividing into the **radial** and **ulnar** arteries in the cubital fossa. * **Nutrient Artery:** The brachial artery provides the nutrient artery to the **humerus**. * **Clinical Correlation:** The brachial artery is the most common site for recording blood pressure and is medial to the biceps tendon in the cubital fossa (Medial to Lateral: **M**edian nerve, **B**rachial artery, **B**iceps tendon, **R**adial nerve - Mnemonic: **MBBR**). * **Supracondylar Fracture:** This fracture of the humerus can lead to brachial artery injury, potentially causing **Volkmann’s Ischemic Contracture**.

Question 78: Which nerve supplies the deep flexors of the forearm?

A. Median nerve
B. Ulnar nerve (Correct Answer)
C. Radial nerve
D. Musculocutaneous nerve

Explanation: ### Explanation The **deep flexors of the forearm** consist of three muscles: Flexor Digitorum Profundus (FDP), Flexor Pollicis Longus (FPL), and Pronator Quadratus (PQ). The nerve supply to this group is unique because it is shared between the Median and Ulnar nerves. **Why Ulnar Nerve is the correct answer (in the context of this question):** The **Ulnar nerve** supplies the **medial half of the Flexor Digitorum Profundus** (the part acting on the ring and little fingers). While the Median nerve (via the Anterior Interosseous Nerve) supplies the lateral half of FDP, FPL, and PQ, the Ulnar nerve is the specific answer for the medial component of the deep flexor group [1]. In many standard MCQ formats, if "Median nerve" and "Ulnar nerve" are both listed, the question often refers to the dual innervation of the FDP. **Analysis of Incorrect Options:** * **A. Median nerve:** While it supplies the lateral half of FDP and the other two deep muscles (FPL, PQ) via its **Anterior Interosseous branch** [1], the Ulnar nerve is the classic answer for the medial deep flexor. * **C. Radial nerve:** This nerve supplies the **extensor compartment** of the forearm. * **D. Musculocutaneous nerve:** This nerve supplies the muscles of the **anterior compartment of the arm** (Biceps, Coracobrachialis, Brachialis). **High-Yield Clinical Pearls for NEET-PG:** * **Hybrid Muscle:** The Flexor Digitorum Profundus is a "hybrid" or "composite" muscle because it has a dual nerve supply (Median and Ulnar). * **Ulnar Paradox:** In high ulnar nerve palsy, the clawing of the hand is *less* pronounced because the medial half of the FDP is paralyzed, losing the finger flexion that exacerbates clawing. * **Anterior Interosseous Nerve (AIN):** A branch of the Median nerve; it supplies all deep flexors *except* the medial half of FDP [1]. Injury to AIN results in the inability to make the "OK" sign (Kiloh-Nevin syndrome).

Question 79: A physician notes weakness of a patient's thumb in extension, while rotation, flexion, abduction, adduction, and opposition remain normal. Which of the following nerves is most likely involved?

A. Median and radial
B. Median and ulnar
C. Median only
D. Radial only (Correct Answer)

Explanation: ### Explanation **1. Why "Radial only" is correct:** The movement described as deficient is **thumb extension**. Extension of the thumb occurs at the metacarpophalangeal (MCP) and interphalangeal (IP) joints, mediated by two primary muscles [1]: * **Extensor Pollicis Longus (EPL)** [2] * **Extensor Pollicis Brevis (EPB)** [2] Both of these muscles are located in the posterior compartment of the forearm and are innervated by the **Posterior Interosseous Nerve (PIN)**, which is the deep branch of the **Radial Nerve** [2]. Since all other movements (flexion, abduction, adduction, opposition) are intact, the lesion is isolated to the radial nerve supply [1]. **2. Why other options are incorrect:** * **Median Nerve:** This nerve supplies the muscles of the thenar eminence (Opponens pollicis, Abductor pollicis brevis, and Flexor pollicis brevis) [1]. If the median nerve were involved, the patient would struggle with **opposition, abduction, and flexion** [1]. * **Ulnar Nerve:** This nerve supplies the **Adductor pollicis** [1]. If involved, the patient would show weakness in thumb adduction (and a positive Froment’s sign). * **Combinations (A & B):** Since rotation (opposition), flexion, abduction, and adduction are normal, the median and ulnar nerves must be fully functional. **3. Clinical Pearls & High-Yield Facts:** * **PIN Palsy vs. Radial Nerve Palsy:** In Posterior Interosseous Nerve (PIN) injury, there is "finger drop" (loss of extension) but **no sensory loss**, as the PIN is purely motor. * **The "Hitchhiker’s Thumb":** Extension of the thumb is the classic test for the integrity of the radial nerve/PIN. * **Anatomical Snuffbox:** The Extensor Pollicis Longus (medial) and Extensor Pollicis Brevis/Abductor Pollicis Longus (lateral) form the boundaries of the snuffbox [2]. All are radial-innervated [2].

Question 80: A patient can extend his wrist but cannot extend the metacarpophalangeal joint of his hand after an accident. Sensation in the limb is normal. At which level is the affected nerve likely injured?

A. At coracobrachialis
B. Head of radius (Correct Answer)
C. Spiral groove
D. Surgical neck of humerus

Explanation: The clinical presentation describes a classic case of **Posterior Interosseous Nerve (PIN)** palsy. ### Why "Head of Radius" is Correct The Radial nerve divides into a superficial (sensory) branch and a deep (motor) branch at the level of the lateral epicondyle. The deep branch, known as the **Posterior Interosseous Nerve (PIN)**, enters the posterior compartment of the forearm by passing through the **Arcade of Frohse** (supinator muscle), which lies near the **head of the radius**. * **The "Wrist Drop" vs. "Finger Drop" Concept:** The PIN supplies all extensors of the forearm *except* the Brachioradialis, Extensor Carpi Radialis Longus (ECRL), and sometimes the ECRB. These muscles are supplied by the main Radial nerve *above* the elbow. * In this patient, the ECRL is intact, allowing for **wrist extension** (often with radial deviation). However, the Extensor Digitorum is paralyzed, preventing **metacarpophalangeal (MCP) joint extension**. * Since the superficial radial nerve is spared, **sensation remains normal**. ### Why Other Options are Incorrect * **A. Coracobrachialis:** This is the site of the Musculocutaneous nerve; injury here would affect elbow flexion and lateral forearm sensation. * **C. Spiral Groove:** Injury here causes **complete Radial Nerve Palsy**, resulting in "Wrist Drop" (loss of both wrist and finger extension) and sensory loss in the first dorsal web space. * **D. Surgical Neck of Humerus:** This is the site of the Axillary nerve; injury leads to deltoid paralysis and loss of sensation over the "regimental badge" area. ### NEET-PG High-Yield Pearls * **PIN Palsy:** Finger drop + Normal sensation + Intact wrist extension (Radial deviation). * **Radial Nerve at Spiral Groove:** Wrist drop + Sensory loss. * **Saturday Night Palsy:** Compression at the axilla; involves Triceps (loss of elbow extension) + Wrist drop. * **PIN vs. Radial Nerve:** If the patient can extend the wrist but not the fingers, the lesion is always distal to the origin of the ECRL (i.e., at or below the elbow).

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Upper Limb — MCQs

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