Okay, let's see. The question is about a 25-year-old man with a lesion of the dorsal scapular nerve, leading to inability to adduct the scapula. I need to figure out which muscle is paralyzed.

First, I remember that the dorsal scapular nerve is a branch of the brachial plexus, specifically from the C5 root. It innervates the rhomboid muscles, right? The rhomboids major and minor are responsible for retracting the scapula, which is adduction towards the spine. So if the dorsal scapular nerve is damaged, those muscles would be affected.

Wait, the options are A to D, but the user didn't list them. Oh right, the original question had the options A-D but they're empty here. But the correct answer is supposed to be one of the muscles innervated by the dorsal scapular nerve. The main muscle is the rhomboid major. Maybe the options included other muscles like the trapezius, levator scapulae, or serratus anterior. Let me think: the trapezius is innervated by the accessory nerve and spinal accessory nerve, so that's not it. The serratus anterior is from the long thoracic nerve. The levator scapulae is from C3-C5 dorsal rami. So the correct answer is rhomboid major.

So the wrong options would be other scapular muscles. The user probably had options like A. Trapezius, B. Serratus anterior, C. Levator scapulae, D. Rhomboid major. Then D is correct. Let me structure the explanation accordingly.

Core Concept: The dorsal scapular nerve innervates the rhomboid major and minor, which are responsible for scapular retraction. Damage leads to inability to adduct the scapula.

Why Correct: The dorsal scapular nerve (C5) supplies the rhomboids. Paralysis here causes loss of scapular retraction, leading to winging when trying to adduct.

Wrong Options: Trapezius (accessory nerve), Serratus anterior (long thoracic), Levator scapulae (C3-C5 dorsal rami). Each has different innervation.

Clinical Pearl: Remember "Dorsal to Rhomboid" – dorsal scapular nerve to rhomboid muscles. Winging of scapula on adduction is a key sign.

**Core Concept:** The dorsal scapular nerve, a branch of the C5 spinal nerve root, innervates the rhomboid major and minor muscles. These muscles are primary retractors of the scapula, essential for adduction (pulling the scapula medially toward the spine).

**Why the Correct Answer is Right:** The dorsal scapular nerve directly supplies the **rhomboid major** muscle, which is the primary muscle responsible for scapular retraction. When this nerve is damaged, the rhomboid major loses function, leading to an inability to adduct the scapula. This results in a characteristic "winging" of the scapula when the patient attempts to push against resistance.

**Why Each Wrong Option is Incorrect:**
**Option A (Trapezius):** Innervated by the spinal accessory nerve (cranial nerve

✓ Correct Answer: B. Rhomboid major