8. Vestibular and Auditory Systems


VIII travels with VII en route to brainstem


Vestibular System

A.        Inner Ear

- petrous portion of temporal bone

- semicircular ducts

- utricle (static+horizontal)

- saccule (vertical motion)

- epithelium

- stereocilia

- deflection toward tallest cilia depolarization

B.        CN VIII

C.        Clinical Correlations

                                                                i.      nystagmus

                                                              ii.      benign paroxysmal positional vertigo

                                                             iii.      labyrinthitis

                                                              iv.      Menieres disease

                                                               v.      vestibulotoxicity

                                                              vi.      schwannoma


Auditory System

A.        Outer Ear

B.        Middle Ear

bones: malleus, incus, stapes

muscles: tensor tympani, stapedius

a.         Clinical Correlations

                                                                            i.      conductive hearing loss

                                                                          ii.      otitis media

                                                                         iii.      tympanic membrane perforation

                                                                          iv.      meningitis

C.        Inner Ear

- cochlea

- oval window scala vestibuli scala tympani oval window

- high frequency low frequency

- scala media (filled with endolymphatic fluid)

- hair cells, tectorial membrane

- single inner row of hair cells (most important)

D.        CN VIII

E.        Clinical Correlations