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Cranial Nerves

Last Updated: 10/10/18

Index

  1. Cranial Nerves: Basic Facts About
  2. Cranial Nerves: And NF2
  3. Cranial Nerves: Functions
    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

Cranial Nerves: Basic Facts About

A cranial nerve (CN) is any of the twelve (12) paired nerves that arise from the lower surface of the brain with one of each pair on each side and pass through openings in the skull to the periphery of the body. [1]

The twelve cranial nerves include; 1) olfactory nerve, 2) optic nerve, 3) oculomotor nerve, 3) trochlear nerve, 4) trigeminal nerve, 5) abducens nerve, 6) facial nerve, 7) vestibulocochlear nerve, 8) glossopharyngeal nerve, 9) vagus nerve, 10) spinal accessory nerve, 11) and hypoglossal nerve. [1]

Cranial Nerves: And NF2

For individual's with neurofibromatosis type 2 (NF2), schwannoma tumors grow as a part of up to eight (8) of the brains twelve (12) cranial nerves. Some individuals with NF2 only develop tumors on one pair of cranial nerves. Variations of how and when tumors develop vary from person to person.

The hallmark location often used as part of the diagnosis criteria for individuals with NF2, are tumors along cranial nerve 8 (CN8), the vestibulocochlear nerve. The functions of CN8 are hearing and balance. Growth of tumors along CN8 can also damage CN7, the facial nerve. The function of CN7 is facial expression.

The complete list of cranial nerves individuals with NF2 commonly develop tumors on include:[1]

  • CN3: oculomotor
  • CN4: trochlear
  • CN5: trigeminal
  • CN6: abducens
  • CN7: facial
  • CN8: vestibulocochlear
  • CN9: glossopharyngeal
  • CN10: vagal
  • CN12: hypoglossal
  • CN11: spinal accessory

Cranial Nerves: Functions

Each of the cranial nerves controls a specific function, sense, or sometimes both.

  1. CN I (Olfactory Nerve): Meets brainstem at the Olfactory bulb for the sense of smell
  2. CNI (Cranial Nerve 1), is the only Cranial Nerve that can regenerate completely if damaged.

  3. CN II (Optic Nerve): Meets brainstem at the Lateral Geniculate nucleus for vision
  4. CNII (Cranial Nerve 2), carries Vision to the brain. This nerve does not contain Schwann cells.

  5. CN III (Oculomotor Nerve): Meets brainstem at the Oculomotor nucleus and Edinger-Westphal nucleus for the muscles of the eye
  6. CN3, (Cranial Nerve 3) has two functions it controls:

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

  7. CN IV (Trochlear Nerve): Meets brainstem at the Trochlear nucleus, muscles for eye movement
  8. CN IV (Cranial Nerve 4), controls eyeball movement, rotating, up, down, left and right.

  9. CN V (Trigeminal Nerve), three (3) branches: Meets brainstem at the Mesencephalic nucleus, Principal sensory nucleus, Spinal trigeminal nucleus, and Trigeminal motor nucleus.
    • Ophthalmic Nerve (V1): Muscles of 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): Meets brainstem at the Abducens nucleus for eye movement.
  11. Lateral Rectus Muscle: lateral vision

  12. CN VII (Facial Nerve): Meets brainstem at the Facial motor nucleus, Superior salivatory nucleus, and Solitary nucleus.
    • 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): Meets brainstem at the Vestibular nuclei (w. subnuclei) and Cochlear nucleus (w. subnuclei).
    • Cochlear Nerve: Hearing
    • Vestibular Nerve: Balance

  14. CN IX (Glossopharyngeal Nerve): Meets brainstem at the Solitary nucleus, the Spinal nucleus of the trigeminal nerve, lateral nucleus of vagal trigone, Nucleus ambiguus, and Inferior salivatory nucleus for muscles of the tongue, tonsil, and 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): Meets brainstem at the Dorsal nucleus of vagus nerve, Nucleus ambiguus, Solitary nucleus, and Spinal trigeminal nucleus.
    • 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): Meets brainstem at the Spinal accessory nucleus, and Nucleus ambiguus for muscles used in neck and shoulder movement.

  17. CN XII (Hypoglossal Nerve): Meets brainstem at the Hypoglossal nucleus for muscles of the tongue.

Source

  1. Merriam-Webster Definitions. www.merriam-webster.com
  2. Deora, Harsh, et al. "Rare cranial nerve schwannomas: A retrospective review of nontrigeminal, nonvestibular cranial nerve schwannomas." Journal of Neurosciences in Rural Practice 9.2 (2018): 258
    http://www.ruralneuropractice.com/article.asp?issn=0976-3147;year=2018;volume=9;issue=2;spage=258;epage=263;aulast=Deora