Cranial Nerves

Last Updated: 03/28/17

Cranial Nerves, Brain, numbered, brainstem, CN I, CN1, Olfactory Nerve, CN II, CN2, Optic Nerve, CN III, CN3, Oculomotor Nerve, CN IV, CN4, Trochlear Nerve, CN V, CN5, Trigeminal Nerve, CN VI, CN 6, Abducens Nerve, CN VII, CN7, Facial Nerve, CN VIII, CN8, Vestibulocochlear Nerve, CN IX, CN9, Glossopharyngeal Nerve, CN X, CN10, Vagus Nerve, CN XI, CN11, Spinal Accessory Nerve, CN XII, CN12, Hypoglossal Nerve
  1. CN I: Olfactory Nerve
  2. CN II: Optic Nerve
  3. CN III: Oculomotor Nerve
  4. CN IV: Trochlear Nerve
  5. CN V: Trigeminal Nerve
  6. CN VI: Abducens Nerve
  7. CN VII: Facial Nerve
  8. CN VIII: Vestibulocochlear Nerve
  9. CN IX: Glossopharyngeal Nerve
  10. CN X: Vagus Nerve
  11. CN XI: Spinal Accessory Nerve
  12. CN XII: Hypoglossal Nerve

For individual's with NF2, tumors are expected to grow on Cranial Nerve 8 (CN 8) - Vestibulocochlear Nerve; which controls hearing and balance. It is not uncommon for tumors on CN 8, to also damage CN 7 the Facial Nerve. Tumors also commonly grow on the; Optic Nerve (CN 2), the Trigeminal Nerve (CN 5), and Vagus Nerve (CN 10). It is possible for tumors to grow and damage any other cranial nerves as well. These nerves are sometimes damaged as a result of Schwannoma, tumors that grow as a part of a nerve, but damage can also be the result of Meningioma, tumors that cause damage as a result of intracranial pressure.

Many Cranial Nerves have more than one function, for example when a Schwannoma grows on the Vestibular Nerve; it results in loss of function of Hearing and Balance, since the Vestibular Nerve is very close to the Cochlear Nerve.

There are 12 pairs of nerves in the Central Nerve System, a left and a right nerve for each. Some control muscles and others control senses. The Cranial Nerves (CN) include:

  1. CN I - Olfactory Nerve: Sensation of Smell
  2. CNI (Cranial Nerve 1), is the only Cranial Nerve that can regenerate completely if damaged.

  3. CN II - Optic Nerve: Vision
  4. CNII (Cranial Nerve 2), carries Vision to the brain. This nerve does not contain Schwann cells.

  5. CN III - Oculomotor Nerve: Muscles for the Eye
  6. CN3, (Cranial Nerve 3) has two functions it controls:

    • Levator Palpebrae Superioris Muscle: this muscle keeps the eyelids open
    • Constriction of the Pupils: adaption to changing light

  7. CN IV - Trochlear Nerve: Muscles for Eye Movement
  8. CN IV (Cranial Nerve 4), controls eyeball movement, rotating, up, down, left and right.

  9. CN V - Trigeminal Nerve: 3 Nerve Branches:
    • Ophthalmic Nerve (V1): Muscles for the eyelids, eyebrow, forehead and nose.
      This branch affects the glands for tear production and mucous membrane of the nasal cavity.
    • Maxillary Nerve (V2): Sensation from the maxillary, nasal cavity, sinuses and taste.
    • Mandibular Nerve (V3): Face Sensations and Muscles for biting, chewing, and swallowing.

  10. CN VI - Abducens Nerve: Eye Movement
  11. Lateral Rectus Muscle: lateral vision

  12. CN VII - Facial Nerve:
    • Muscle Control: Facial Expression
    • Sensory Control: Taste sensations for the front 2/3 of the tongue; sensations of Sweet and Salty

  13. CN VIII - Vestibulocochlear Nerve:
    • Cochlear Nerve: Hearing
    • Vestibular Nerve: Balance

  14. CN IX - Glossopharyngeal Nerve: Tongue, Tonsil, Pharynx
    • Muscle Control: Control of the Stylopharyngeus Muscle, impairment of this muscles can affect swallowing and speech.
    • Sensory Control: Taste sensations from the back 1/3 of the tongue; sensations of Bitter and Sour

  15. CN X - Vagus Nerve:
    • Muscle Control: Muscle control that controls heart rate, sweating, esophagus and digestion, as well as many involuntary muscle movements in the mouth, including speech and breathing.
    • Sensory Control: Feeling in the ear canal.

  16. CN XI - Spinal Accessory Nerve: Controls muscles used in neck and shoulder movement.

  17. CN XII - Hypoglossal Nerve: Controls muscles of tongue.
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