Cranial Nerve 8

Aka: Cranial Nerve 8, Cranial Nerve VIII, Acoustic Nerve, Cochlear Nerve, Vestibular Nerve, Vestibulocochlear Nerve, CN 8

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II. Anatomy

  1. entEarVestibularCochlearNerveGrayBB928.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)

III. Course

  1. neuroAcousticCn8.png
  2. Originates as two separate nuclei in the Medulla
    1. Cochlear nucleus (innervates Organ of Corti)
    2. Vestibular nucleus (innervates semicircular canals)
  3. Fibers from both nerves join to form one trunk
  4. Passes via Internal Auditory Canal to their respective somatic sensory ganglia
    1. Spiral Ganglion (Hearing)
    2. Vestibular Ganglion (balance)
  5. Auditory signals partially cross the midline
    1. Each ear's auditory signals are transmitted to both Cerebral Hemispheres
    2. Fibers Synapse at multiple locations (inferior colliculus, medial geniculate body)

IV. Exam

  1. Cochlear Nerve
    1. See Hearing Testing
  2. Vestibular Nerve
    1. See Vestibular Testing (Labyrinthine testing)
    2. Spontaneous Nystagmus

V. References

  1. Gilman (1989) Manter and Gatz Essentials of Neuroanatomy and Neurophysiology, Davis, p. 87-113
  2. Goldberg (2014) Clinical Neuroanatomy, p. 24-39
  3. Netter (1997) Atlas Human Anatomy, ICON Learning, p. 110-129

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