Dorsal Scapular Nerve and Brachial Plexus Injuries: Anatomy, Examination, and Clinical Implications скачать в хорошем качестве

Dorsal Scapular Nerve and Brachial Plexus Injuries: Anatomy, Examination, and Clinical Implications

Join this channel to support the channel    / @nabilebraheim   Dorsal Scapular Nerve and Brachial Plexus Injuries The dorsal scapular nerve arises from the C5 nerve root and innervates the rhomboid major, rhomboid minor, and levator scapulae muscles. The levator scapulae elevates the scapula and tilts the glenoid cavity inferiorly by rotating the scapula. The rhomboid major and minor muscles connect the medial edge of the scapula to the spinal column. The rhomboids pull the scapula towards the midline (scapular adduction) and also pull the scapula superiorly with inward rotation. This movement opposes the action of the serratus anterior muscle, which is supplied by the long thoracic nerve. The dorsal scapular nerve passes dorsally, perforating the middle scalene muscle, then travels along the undersurface of the levator scapulae to reach the rhomboid muscles. Injury to the dorsal scapular nerve can cause scapular winging. The scapula may become displaced with upward rotation. Examination of the Rhomboids: Ask the patient to bring the shoulder and scapula together posteriorly. Palpate the contracted rhomboid muscles during this movement. Brachial Plexus Injury: Preganglionic Injury: This involves root avulsion, which has the worst prognosis. It is usually associated with Horner’s syndrome (ptosis, miosis, anhidrosis) due to disruption of the sympathetic chain. Medial winging of the scapula may occur due to involvement of the long thoracic nerve. There is also loss of muscle function supplied by the dorsal scapular nerve (C5) and possibly other cervical nerves such as C3 and C4, which supply the levator scapulae. Electromyography (EMG) in this situation shows loss of activity in the cervical paraspinal muscles. This finding is significant as it indicates a preganglionic injury with a poor prognosis. The histamine test will be normal in these conditions. Quizzes 1. Which nerve innervates the rhomboid major and minor muscles? A) Long thoracic nerve B) Dorsal scapular nerve C) Suprascapular nerve D) Axillary nerve Explanation: The dorsal scapular nerve, originating from the C5 nerve root, innervates both the rhomboid major and minor muscles, facilitating scapular retraction. 2. What is the primary function of the levator scapulae muscle? A) Depresses the scapula B) Elevates the scapula and tilts the glenoid cavity inferiorly C) Protracts the scapula D) Rotates the scapula upward Explanation: The levator scapulae elevates the scapula and rotates it to tilt the glenoid cavity downward, aiding in shoulder movements. 3. Through which muscle does the dorsal scapular nerve pass after its origin? A) Anterior scalene B) Middle scalene C) Posterior scalene D) Sternocleidomastoid Explanation: After originating from the C5 nerve root, the dorsal scapular nerve pierces the middle scalene muscle before innervating its target muscles. 4. Injury to the dorsal scapular nerve may result in which condition? A) Lateral scapular winging B) Scapular winging with upward rotation C) Inferior displacement of the scapula D) Scapular protraction Explanation: Damage to the dorsal scapular nerve can cause weakness in the rhomboid muscles, leading to scapular winging characterized by upward rotation and medial border prominence. 5. How can the function of the rhomboid muscles be clinically assessed? A) Ask the patient to retract the scapulae and palpate for muscle contraction B) Observe for scapular elevation during arm abduction C) Test resistance against shoulder flexion D) Check for scapular depression during arm extension Explanation: To assess the rhomboids, the patient is instructed to retract (pull together) the scapulae, and the examiner palpates the muscles to feel for contraction. 6. Which syndrome is commonly associated with preganglionic brachial plexus injuries? A) Carpal tunnel syndrome B) Horner’s syndrome C) Thoracic outlet syndrome D) Cubital tunnel syndrome Explanation: Preganglionic injuries can disrupt the sympathetic chain, leading to Horner’s syndrome, characterized by ptosis, miosis, and anhidrosis. 7. What are the typical signs of Horner’s syndrome? A) Exophthalmos and dry mouth B) Ptosis, miosis, and anhidrosis C) Diplopia and lacrimation D) Mydriasis and hyperhidrosis Explanation: Horner’s syndrome presents with ptosis (drooping eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) on the affected side. 8. Which nerve, when injured, can lead to medial scapular winging? A) Long thoracic nerve B) Dorsal scapular nerve C) Suprascapular nerve D) Axillary nerve Explanation: The long thoracic nerve innervates the serratus anterior muscle; injury to this nerve can cause medial scapular winging due to muscle paralysis.