Medicine & USMLE

Vagus Nerve (CN X)

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Cranial Nerves
  1. Olfactory Nerve (CN I)
  2. Optic Nerve (CN II)
  3. Oculomotor Nerve (CN III)
  4. Trochlear Nerve (CN IV)
  5. Trigeminal Nerve (CN V)
  6. Abducens Nerve (CN VI)
  7. Facial Nerve (CN VII)
  8. Vestibulocochlear Nerve (CN VIII)
  9. Glossopharyngeal Nerve (CN IX)
  10. Vagus Nerve (CN X)
  11. Accessory Nerve (CN XI)
  12. Hypoglossal Nerve (CN XII)

Summary

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Key Points

  • Vagus Nerve (Cranial Nerve X)
    • Nerve type
      • Motor
      • Sensory
    • Function
      • Controls muscles for swallowing, soft palate elevation, coughing
        • Test by asking patient to swallow
      • Talking (vocal cords)
        • Via recurrent laryngeal and superior laryngeal branches
        • The RLN can be injured during thyroid surgery (e.g. a thyroidectomy) due to close proximity to inferior thyroid artery
      • Midline uvula
        • Test symmetry by asking patient to stick tongue out and say “ah”
          • Uvula deviates away from lesion if present
      • Visceral sensation/afferents
        • Including aortic arch baro/chemoreceptors
          • Goes to nucleus solitarius in medulla
      • Taste and sensation in supra/epiglottic region
      • Parasympathetics to thoracoabdominal viscera
        • Heart, lungs, upper GI tract
      • Cutaneous sensation to posterior external auditory canal
        • Via small auricular branch
        • Sensation to most of external auditory canal is via CN V3
      • Dural meninges sensation
        • Via meningeal branch of nerve
    • Nerve Entry/Exit
      • Exits brainstem from medulla
        • Exits brainstem from postolivary sulcus in medulla
        • Motor output and heart parasympathetics output from nucleus ambiguus in medulla
        • Parasympathetic fibers to viscera besides heart from dorsal nucleus of vagus nerve in medulla
        • Taste, visceral afferents go to the solitary nucleus in medulla
        • Sensation from larynx, outer ear, meninges to the spinal trigeminal nucleus in medulla
    • Cranial foramen
      • Jugular foramen
    • Reflexes
      • Gag reflex (efferent motor)
      • Cough reflex (afferent sensory and efferent motor)