Medicine & USMLE

Hypoglossal Nerve (CN XII)

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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

  • Hypoglossal nerve (Cranial Nerve XII)
    • Nerve type
      • Motor
    • Function
      • Tongue movement
        • Controls all muscles of tongue except for palatoglossus (innervated by CN X)
        • May be stimulated by DBS for treatment of sleep apnea when tongue occlusion of the airway is implicated
        • Test by asking patient to stick tongue out
          • Tongue deviates to side of lesion if present
    • Nerve Entry/Exit
      • Nerve exits medulla at midline
        • Originates from hypoglossal nucleus
          • Located at floor of fourth ventricle
        • Nerve exits at rostral end of the postolivary sulcus
    • Cranial foramen
      • Hypoglossal canal
    • Reflexes
      • None