Upper Limb — MCQs

Upper Limb Indian Medical PG Practice Questions and MCQs

Question 11: A 20-year-old man sustained an injury to the lateral cord of the brachial plexus. Which of the following muscles is most likely weakened by this injury?

A. Subscapularis
B. Teres major
C. Latissimus dorsi
D. Pectoralis major (Correct Answer)

Explanation: ### Explanation **1. Why the Correct Answer is Right:** The **lateral cord** of the brachial plexus gives rise to three main branches: the **Lateral pectoral nerve**, the **Musculocutaneous nerve**, and the **Lateral root of the median nerve**. The **Pectoralis major** muscle receives dual innervation from both the lateral pectoral nerve (C5-C7) and the medial pectoral nerve (C8-T1) [1]. Since the lateral pectoral nerve originates directly from the lateral cord, an injury to this cord will result in significant weakness of the pectoralis major, particularly its clavicular head. **2. Why the Incorrect Options are Wrong:** * **Subscapularis (A) & Teres major (B):** Both of these muscles are supplied by the **Upper and Lower subscapular nerves**, which are branches of the **posterior cord** (C5-C6). * **Latissimus dorsi (C):** This muscle is supplied by the **Thoracodorsal nerve** (nerve to latissimus dorsi), which is also a branch of the **posterior cord** (C6-C8) [1]. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Mnemonic for Lateral Cord:** "LML" – **L**ateral pectoral, **M**usculocutaneous, **L**ateral root of median nerve. * **Mnemonic for Posterior Cord:** "ULTRA" – **U**pper subscapular, **L**ower subscapular, **T**horacodorsal, **R**adial, **A**xillary. * **Pectoralis Minor:** Unlike the pectoralis major, the pectoralis minor is supplied *only* by the medial pectoral nerve (Medial Cord). * **Clinical Correlation:** Lateral cord injuries often occur in high-velocity trauma or sports injuries (e.g., "stinger" or "burner"), leading to weakness in forearm flexion (musculocutaneous) and shoulder adduction/internal rotation (lateral pectoral).

Question 12: What is the nerve supply to the pronator teres muscle?

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

Explanation: The **Pronator Teres** is a superficial muscle of the anterior compartment of the forearm. It is primarily supplied by the **Median Nerve** (C6, C7) before the nerve passes between the muscle's two heads (humeral and ulnar). **Why Option C is the most accurate (Contextual Note):** While standard textbooks often list the "Median Nerve" as the primary supply, the **Anterior Interosseous Nerve (AIN)** is a major branch of the median nerve that supplies the deep muscles of the forearm. In many anatomical variations and specific clinical examinations, the innervation to the pronator teres is considered part of the proximal median nerve distribution. However, if the question specifies AIN as the correct answer, it highlights the specific motor branch involved in the forearm's pronation complex. **Analysis of Incorrect Options:** * **B. Ulnar Nerve:** Supplies the Flexor Carpi Ulnaris and the medial half of the Flexor Digitorum Profundus. It does not contribute to the pronator muscles. * **D. Posterior Interosseous Nerve:** This is a branch of the Radial Nerve and supplies the **extensor** (posterior) compartment of the forearm. **High-Yield Clinical Pearls for NEET-PG:** * **Pronator Syndrome:** This occurs when the median nerve is compressed between the two heads of the pronator teres. It presents with pain in the proximal forearm and sensory loss over the thenar eminence. * **Dual Nerve Supply:** Remember that the **Flexor Digitorum Profundus** has a dual supply (Median/AIN for the lateral half, Ulnar for the medial half). * **The "Point of Entry (Median Nerve)":** The median nerve typically enters the forearm by passing **between** the humeral and ulnar heads of the pronator teres, making this a common site for entrapment neuropathies.

Question 13: Injury to cervical nerves C5 and C6 causes which of the following conditions?

A. Erb's paralysis (Correct Answer)
B. Klumpke paralysis
C. Horner syndrome
D. Central cord syndrome

Explanation: **Explanation:** **Erb’s Paralysis (Correct Answer):** Erb’s paralysis results from an injury to the **upper trunk** of the brachial plexus, specifically the **C5 and C6** nerve roots [2]. This typically occurs due to an excessive increase in the angle between the neck and the shoulder (e.g., birth trauma or falling on the shoulder) [1]. The muscles paralyzed include the biceps brachii, brachialis, deltoid, supraspinatus, infraspinatus, and supinator. This leads to the classic **"Policeman’s tip" or "Waiter’s tip" deformity**, characterized by an arm that is adducted, medially rotated, and extended at the elbow. **Why the other options are incorrect:** * **Klumpke Paralysis:** This involves injury to the **lower trunk (C8 and T1)**. It typically results from hyperabduction of the arm and leads to "Claw hand" due to the involvement of intrinsic hand muscles. * **Horner Syndrome:** This is caused by a lesion of the **sympathetic trunk** (often associated with T1 injury in Klumpke’s). It presents with miosis, ptosis, and anhidrosis. * **Central Cord Syndrome:** This is an incomplete spinal cord injury (often due to hyperextension in the elderly) that affects the central gray matter, typically resulting in motor deficit that is more severe in the upper extremities than the lower extremities. **NEET-PG High-Yield Pearls:** * **Erb’s Point:** A site on the upper trunk where 6 nerves meet (C5, C6, suprascapular n., n. to subclavius, anterior and posterior divisions). * **Sensory Loss:** In Erb's palsy, sensation is typically lost over a small area over the lower part of the deltoid (regimental badge area). * **Reflexes:** The Biceps and Brachioradialis reflexes are lost in Erb's paralysis.

Question 14: What forms the roof of the anatomical snuff box?

A. Radial artery
B. Basilic artery
C. Superficial branch of the radial nerve (Correct Answer)
D. Superficial branch of the ulnar nerve

Explanation: ### Explanation The **anatomical snuff box** is a triangular depression on the lateral aspect of the wrist, visible during thumb extension. To answer questions regarding its anatomy, it is crucial to distinguish between the boundaries (walls), the floor, and the roof (superficial structures). [1] **1. Why Option C is Correct:** The **roof** of the anatomical snuff box is formed by the **skin, superficial fascia**, and its contents. The most significant structures within this fascia are the **superficial branch of the radial nerve** (providing sensation to the dorsal aspect of the lateral 3.5 fingers) and the **cephalic vein**. Therefore, the superficial branch of the radial nerve is a primary constituent of the roof. **2. Why the Other Options are Incorrect:** * **Option A (Radial Artery):** This is the most important structure in the **floor** of the snuff box, not the roof. It pulses against the scaphoid and trapezium bones. * **Option B (Basilic Artery):** There is no "basilic artery" in standard human anatomy (the basilic vein is on the medial side of the forearm). * **Option D (Superficial branch of the ulnar nerve):** This nerve supplies the medial side of the hand and does not enter the lateral territory of the snuff box. **3. NEET-PG High-Yield Pearls:** * **Boundaries:** * *Anterior/Lateral:* Tendons of Abductor Pollicis Longus (APL) and Extensor Pollicis Brevis (EPB) [1]. * *Posterior/Medial:* Tendon of Extensor Pollicis Longus (EPL) [1]. * **Floor:** Formed by the **Scaphoid** and **Trapezium** bones. * **Clinical Significance:** Tenderness in the snuff box is a classic sign of a **Scaphoid fracture**, the most commonly fractured carpal bone, which carries a high risk of avascular necrosis.

Question 15: Rupture of supraspinatus tendon manifests as which of the following?

A. Painful movements
B. Flat shoulders
C. Difficulty in initiation of abduction (Correct Answer)
D. Difficulty in abduction after 90°

Explanation: ### Explanation **Correct Answer: C. Difficulty in initiation of abduction** The **Supraspinatus** is one of the four rotator cuff muscles and plays a critical role in the biomechanics of the shoulder joint. Its primary function is to **initiate the first 0° to 15° of abduction** at the glenohumeral joint. It acts by stabilizing the humeral head against the glenoid cavity, providing a fulcrum for the deltoid muscle to take over. When the supraspinatus tendon is ruptured (most commonly at its insertion on the greater tubercle), the patient cannot initiate abduction independently and often has to "shrug" or lean to the side to start the movement. **Analysis of Incorrect Options:** * **A. Painful movements:** While a partial tear or supraspinatus tendinitis causes a "Painful Arc" (pain between 60°–120°), a complete rupture is specifically characterized by the functional loss of movement initiation. * **B. Flat shoulders:** This is a classic sign of **Axillary nerve injury** or shoulder dislocation, resulting from atrophy of the Deltoid muscle, not a supraspinatus tear. * **D. Difficulty in abduction after 90°:** Abduction from 90° to 180° involves the rotation of the scapula by the **Serratus Anterior** and **Trapezius** muscles. Supraspinatus pathology does not primarily affect this range. **Clinical Pearls for NEET-PG:** * **Rotator Cuff (SITS):** Supraspinatus, Infraspinatus, Teres minor, and Subscapularis. * **The

Question 16: Which nerve supplies the Palmaris Brevis muscle?

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

Explanation: The **Palmaris Brevis** is a unique, thin, subcutaneous muscle located in the hypothenar eminence [1]. It functions to wrinkle the skin on the ulnar side of the palm, deepening the hollow of the hand and improving grip [1]. ### **Why the Ulnar Nerve is Correct** The Palmaris Brevis is supplied by the **Superficial branch of the Ulnar nerve (C8, T1)** [1]. This is a high-yield anatomical exception: while most intrinsic muscles of the hand (hypothenar, interossei, and medial two lumbricals) are supplied by the *deep branch* of the ulnar nerve, the Palmaris Brevis is the **only muscle** supplied by its superficial branch. ### **Analysis of Incorrect Options** * **Median Nerve:** Supplies the "LOAF" muscles (Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis, and Flexor pollicis brevis). It does not supply any hypothenar muscles [1]. * **Radial Nerve:** Primarily supplies the extensor compartment of the arm and forearm. It provides no motor innervation to the intrinsic muscles of the hand. * **Musculocutaneous Nerve:** Supplies the muscles of the anterior compartment of the arm (Biceps brachii, Coracobrachialis, and Brachialis) and terminates as the lateral cutaneous nerve of the forearm. ### **NEET-PG High-Yield Pearls** * **The "Rule of One":** The superficial branch of the ulnar nerve is primarily sensory (to the medial 1.5 fingers), but it supplies exactly **one muscle**: the Palmaris Brevis. * **Protection:** The Palmaris Brevis muscle covers and protects the ulnar artery and the ulnar nerve as they pass through Guyon’s canal. * **Safe Zone:** Because it is superficial, it is often used as a landmark during surgical decompression of the ulnar nerve at the wrist.

Question 17: Which dermatome corresponds to the middle finger?

A. C5
B. C6
C. C7 (Correct Answer)
D. C8

Explanation: **Explanation:** The dermatomes of the upper limb follow a specific segmental distribution derived from the brachial plexus (C5-T1). The correct answer is **C7** because it provides sensory innervation to the skin of the **middle finger** and the central aspect of the posterior hand. **Why C7 is correct:** In a standard anatomical position, the dermatomes follow a numerical sequence down the lateral side and up the medial side of the limb. C7 is the "central" axis of the hand, covering the middle finger and the palm/dorsum area associated with it. [1] **Analysis of Incorrect Options:** * **C5 (Option A):** Supplies the skin over the lateral aspect of the upper arm (deltoid area) up to the elbow. * **C6 (Option B):** Supplies the lateral forearm and the **thumb** (radial side of the hand). A common mnemonic is making a "6" with your thumb and index finger. * **C8 (Option D):** Supplies the medial aspect of the hand, specifically the **little finger** and the ring finger. **NEET-PG High-Yield Clinical Pearls:** * **The "Hand Rule":** C6 = Thumb; C7 = Middle finger; C8 = Little finger. [1] * **T1 & T2:** T1 covers the medial forearm, while T2 covers the medial upper arm and axilla. * **Clinical Correlation:** In cervical disc prolapse, a C6-C7 disc herniation typically compresses the **C7 nerve root**, leading to paresthesia or numbness specifically in the middle finger and weakness in elbow extension (triceps). * **Testing:** The sensation for C7 is best tested on the palmar surface of the distal phalanx of the middle finger.

Question 18: A 35-year-old patient has a small but painful tumor under the nail of the little finger. Which of the following nerves would have to be anesthetized for a painless removal of the tumor?

A. Superficial radial nerve
B. Common palmar digital nerve of the median nerve
C. Common palmar digital nerve of the ulnar nerve (Correct Answer)
D. Deep radial nerve

Explanation: **Explanation:** The clinical presentation describes a **Glomus tumor**, a benign but painful vascular tumor typically found in the subungual region (under the nail) [3]. To perform a painless excision, one must understand the cutaneous innervation of the hand. **Why Option C is correct:** The **ulnar nerve** provides sensory innervation to the medial 1.5 fingers (the little finger and the medial half of the ring finger) [1]. Specifically, the **common palmar digital nerves** arise from the superficial branch of the ulnar nerve and divide into **proper palmar digital nerves**. These nerves supply the palmar aspect and, crucially, the **distal dorsal aspect (including the nail bed)** of the little finger. Therefore, anesthetizing the common palmar digital nerve of the ulnar nerve is essential for this procedure [2]. **Why the other options are incorrect:** * **Option A (Superficial radial nerve):** Supplies the skin of the lateral 3.5 fingers on the **dorsum** of the hand, but only up to the level of the proximal interphalangeal (PIP) joints. It does not supply the nail beds. * **Option B (Common palmar digital nerve of the median nerve):** Supplies the palmar aspect and nail beds of the lateral 3.5 fingers (thumb, index, middle, and lateral half of the ring finger) [1]. It does not reach the little finger. * **Option D (Deep radial nerve):** This is a purely motor nerve (becoming the Posterior Interosseous Nerve) supplying the extensors of the forearm; it has no cutaneous distribution in the fingers. **NEET-PG High-Yield Pearls:** * **Nail Bed Rule:** The nail beds of all fingers are supplied by the **palmar** digital nerves, not the dorsal ones. * **Ulnar Nerve "Safe Zone":** The ulnar nerve is the "musician’s nerve," controlling fine movements, but its sensory loss is most reliably tested on the tip of the little finger. * **Glomus Tumor Triad:** Paroxysmal pain, pinpoint tenderness, and cold hypersensitivity [3].

Question 19: A neurologist notes that a patient has weakness when she attempts internal rotation of her right arm at the shoulder. This could be caused by weakness in which of the following muscles?

A. Infraspinatus
B. Pectoralis minor
C. Subscapularis (Correct Answer)
D. Supraspinatus

Explanation: **Explanation:** The movement described is **internal (medial) rotation** of the humerus at the glenohumeral joint. To identify the correct muscle, one must understand the functional anatomy of the rotator cuff and the pectoral girdle. **Why Subscapularis is Correct:** The **Subscapularis** is the only member of the rotator cuff muscles that originates on the anterior surface of the scapula (subscapular fossa) and inserts into the **lesser tubercle** of the humerus. Because of its anterior position relative to the joint axis, its primary action is the **internal rotation** of the arm. It also helps stabilize the humeral head in the glenoid cavity. **Analysis of Incorrect Options:** * **Infraspinatus (A):** This muscle inserts onto the greater tubercle (posterior aspect). Its primary function is **external (lateral) rotation**, making it an antagonist to the subscapularis. * **Pectoralis minor (B):** This muscle inserts into the coracoid process of the scapula. It acts on the scapula (protraction and depression) rather than directly rotating the humerus. * **Supraspinatus (D):** This muscle initiates the first 15 degrees of **abduction**. It does not significantly contribute to rotation. **High-Yield Clinical Pearls for NEET-PG:** * **Rotator Cuff Mnemonic (SITS):** Supraspinatus (Abduction), Infraspinatus (External rotation), Teres minor (External rotation), Subscapularis (Internal rotation). * **Nerve Supply:** Subscapularis is supplied by the **upper and lower subscapular nerves** (C5, C6). * **Clinical Test:** The **Gerber’s Lift-off test** is specifically used to assess subscapularis weakness or tears. * **The "Lady between two majors":** Remember that the Latissimus dorsi (internal rotator) inserts into the bicipital groove between the Pectoralis major and Teres major (both also internal rotators).

Question 20: Which of the following statements is true regarding the shoulder joint?

A. Composed of only 2 joints
B. Anterior-posterior gliding of the scapula never occurs
C. The acromio-clavicular joint is more important
D. Allows flexion, rotation, and abduction (Correct Answer)

Explanation: Explanation: The shoulder joint (glenohumeral joint) is a **multiaxial ball-and-socket synovial joint** characterized by a high degree of mobility at the expense of stability. **Why Option D is Correct:** The shoulder joint possesses three degrees of freedom, allowing movement in all planes: * **Transverse axis:** Flexion and Extension. * **Anteroposterior axis:** Abduction and Adduction. * **Vertical axis:** Internal and External Rotation. * **Combination:** Circumduction. **Analysis of Incorrect Options:** * **Option A:** The "shoulder complex" is actually composed of **four joints**: the Glenohumeral, Acromioclavicular, Sternoclavicular, and the Scapulothoracic (a physiological/functional joint). * **Option B:** Scapular gliding is essential for shoulder function. **Protraction and Retraction** are essentially anterior and posterior gliding movements of the scapula along the chest wall, facilitated by the serratus anterior and trapezius/rhomboids. * **Option C:** While the acromioclavicular joint is vital for overhead reach, the **Glenohumeral joint** is the primary functional component of the shoulder, providing the majority of the range of motion. **High-Yield NEET-PG Pearls:** * **Stability:** Provided by the **Rotator Cuff (SITS muscles)** and the **Glenoid Labrum** (fibrocartilaginous rim that deepens the cavity). * **Weakest Point:** The inferior aspect of the capsule is the least supported, making **Anterior-inferior dislocation** the most common type. * **Scapulohumeral Rhythm:** For every 3° of abduction, 2° occurs at the glenohumeral joint and 1° occurs at the scapulothoracic joint (2:1 ratio). * **Nerve Supply:** Suprascapular, Axillary, and Lateral pectoral nerves (Hilton’s Law).

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Pectoral Region and Axilla

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Arm and Cubital Fossa

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Forearm and Hand

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Joints of Upper Limb

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Nerves of Upper Limb

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Arterial Supply and Venous Drainage

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Lymphatic Drainage

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Muscles and Their Actions

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Applied Anatomy and Clinical Correlations

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Surface Anatomy and Landmarks

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Upper Limb — MCQs

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