Updated: 11/16/2018

Musculocutaneous Nerve

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Snapshot
  • A 26-year-old male was riding his bike home when he flipped over his handlebars and landed awkwardly on his neck. He immediately noted the inability to flex his elbow and supinate his forearm. 
Overview
   
Innervation
  • Motor
    • coracobrachialis
    • biceps
    • medial brachialis
  • Sensory
    • lateral antebrachial cutaneous nerve
      • forearm sensory
Origin
  • C5-7
    • superior trunk
      • lateral cord
        • musculocutaneous nerve
          • branch to coracobrachialis
          • branch to biceps
          • branch to brachialis
            • lateral antebrachial cutaneous nerve (terminal branch)
Course
  • Pierces coracobrachialis
    • pierces coracobrachialis 3-8 cm distal to coracoid
    • gives branch to coracobrachialis
  • Splits biceps and brachialis
    • runs between biceps and brachialis in the anterior compartment to enter the lateral aspect of the arm
    • gives branch to biceps and brachialis
  • Pierces deep fascia lateral to biceps brachii
    •  above the elbow, it pierces the deep fascia lateral to the tendon of the biceps brachii
  • Becomes lateral antebrachial cutaneous nerve (terminal branch)
    • emerges laterally to distal bicep tendon and brachioradialis to form the lateral antebrachial cutaneous nerve
Injury & Clinical Conditions
  • Musculocutaneous nerve injury
    • usually iatrogenic
      • at risk during the deltopectoral approach to the shoulder with dissection or retraction medial to the conjoint tendon
    • Can occur as an isolated brachial plexus palsy or in association with another brachial plexus injury 
Treatment
  • Closed injury 
    • can often be treated with watchful waiting and serial electromyographies to ensure that recovery is occurring 
  • Surgical management 
    • if a known laceration has occurred or there is little recovery of elbow flexion, intervention may be required 
    • Oberlin transfer
      • branch of ulnar nerve to the flexor carpi ulnaris can be transferred to the biceps to provide elbow flexion 
    • free innervated muscle transfer
      • the gracilis muscle is often utilized as a free functional muscle transfer in an attempt to regain elbow flexion 
 
 

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