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Nerve & Tendon MCQs

Practice Set 53 of 53

This practice set contains high-yield board review questions covering key concepts in Nerve & Tendon. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 1041

Topic: Nerve & Tendon

A 6-year-old boy sustains a displaced extension-type supracondylar humerus fracture after falling from monkey bars. Post-injury, he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. Which nerve is most likely injured?

. Ulnar nerve
. Radial nerve
. Anterior interosseous branch of the median nerve
. Posterior interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous branch of the median nerve

Explanation

Correct Answer: Anterior interosseous branch of the median nerveThe median nerve is the most frequently injured nerve in extension-type supracondylar humerus fractures. Specifically, the anterior interosseous nerve (AIN), a motor branch of the median nerve, is highly susceptible. AIN palsy presents clinically as the inability to flex the IP joint of the thumb (flexor pollicis longus) and the DIP joint of the index finger (flexor digitorum profundus), resulting in an inability to make an 'OK' sign.

Question 1042

Topic: Nerve & Tendon

A 6-year-old boy falls from a playground structure and sustains a widely displaced extension-type supracondylar humerus fracture. Which of the following nerves is most frequently injured in this specific fracture pattern?

. Radial nerve
. Ulnar nerve
. Median nerve
. Axillary nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Median nerve

Explanation

Correct Answer: Median nerveThe median nerve, specifically its anterior interosseous nerve (AIN) branch, is the most frequently injured nerve in extension-type supracondylar humerus fractures. The radial nerve is the second most commonly injured, often seen with posteromedial displacement. The ulnar nerve is more commonly injured in flexion-type supracondylar fractures or iatrogenically during medial pin placement.

Question 1043

Topic: Nerve & Tendon

A 6-year-old boy falls from the monkey bars and sustains a widely displaced extension-type supracondylar humerus fracture. On examination, he is unable to flex the interphalangeal joint of his thumb and the distal interphalangeal joint of his index finger. Which nerve is most likely injured?

. Radial nerve
. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Musculocutaneous nerve

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

Correct Answer: C (Anterior interosseous nerve)The anterior interosseous nerve (AIN), a motor branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. It innervates the flexor pollicis longus (FPL), the flexor digitorum profundus (FDP) to the index and middle fingers, and the pronator quadratus. Injury results in an inability to make an "OK" sign, as the patient cannot actively flex the IP joint of the thumb and the DIP joint of the index finger.

Question 1044

Topic: Nerve & Tendon

A 6-year-old girl falls from monkey bars and sustains a widely displaced extension-type supracondylar humerus fracture. On examination, she is unable to flex the interphalangeal joint of her thumb and the distal interphalangeal joint of her index finger. Which nerve branch is most likely injured?

. Posterior interosseous nerve
. Anterior interosseous nerve
. Ulnar nerve
. Recurrent motor branch of the median nerve
. Superficial radial nerve

Correct Answer & Explanation

. Anterior interosseous nerve

Explanation

Correct Answer: BThe anterior interosseous nerve (AIN), a motor branch of the median nerve, is the most commonly injured nerve in extension-type supracondylar humerus fractures. AIN palsy presents with the inability to flex the interphalangeal (IP) joint of the thumb (innervating the flexor pollicis longus) and the distal interphalangeal (DIP) joint of the index finger (innervating the flexor digitorum profundus to the index and middle fingers). This leads to an abnormal "A-OK" sign, where the patient pinches with the pulps of the fingers rather than the tips. The median nerve overall is the most frequently injured nerve in these fractures, specifically its AIN branch.

Question 1045

Topic: Nerve & Tendon

A 3-year-old child presents with disproportionate enlargement of the right index and middle fingers. The overgrowth involves both soft tissue and bone, and the fingers exhibit palmar deviation. The overgrowth in this condition is most classically distributed along the territory of which of the following structures?

. Lymphatic vessels
. Median nerve
. Ulnar artery
. Radial nerve
. Dorsal venous arch

Correct Answer & Explanation

. Median nerve

Explanation

Macrodystrophia lipomatosa is a rare, localized form of congenital gigantism characterized by fibrofatty overgrowth that follows the distribution of a specific nerve. In the upper extremity, it most commonly follows the territory of the median nerve.

Question 1046

Topic: Nerve & Tendon

A 4-year-old child presents with disproportionate overgrowth of the index and middle fingers. Imaging shows massive enlargement of the fibrofatty tissue and phalanges strictly localized within the distribution of the median nerve. What is the primary underlying genetic etiology?

. Germline PTEN mutation
. Post-zygotic somatic PIK3CA mutation
. Somatic AKT1 mutation
. NF1 gene microdeletion
. GLI3 gene mutation

Correct Answer & Explanation

. Post-zygotic somatic PIK3CA mutation

Explanation

Macrodystrophia lipomatosa is a localized form of congenital gigantism associated with somatic mosaic mutations in the PIK3CA gene. It typically causes fibrofatty overgrowth along a specific nerve territory, most often the median nerve.

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