A tour of the inner ear

Timothy C. Hain, MD Page last modified: June 18, 2009

Going from through ear structures from the periphery to the central structures, the ear is divided up into three parts - -the external ear, inner ear, and middle ear.

External, Middle and Inner Ear

External Ear

External ear canal
Auricle

Middle Ear

Tympanic Membrane
- TM perforation
- Tympanosclerosis
Ossicles
- Ossicular chain discontinuity
- Otosclerosis
Stapes footplate and round window
- Otosclerosis
The mastoid sinus
- Mastoiditis
The Eustachian Tube
- Eustachian tube dysfunction

Inner Ear

Cochlea
- Disorders
  - Sensorineural hearing loss
    - Hair cell loss or damage
      - Noise trauma
      - Age -- Presbyacusis
      - Toxins -- Vancomycin toxicity
      - Genetic -- many
      - Viruses -- labyrinthitis
      - Vascular: AICA syndrome
Vestibular labyrinth
- Three semicircular canals
- Disorders
  - Trauma
  - Age -- vestibular atelectasis
  - Toxins -- gentamicin toxicity
  - Genetic -- Mondini malformation
  - Viruses -- Vestibular neuritis
  - Vascular: AICA syndrome
Vestibule
- Otolith organs
  - Utricle
  - Saccule
  - Disorders -- little is known
    - Age ?
    - Genetic ?
    - Trauma ?
- Cochlear aqueduct
- Vestibular aqueduct

The 8th nerve and related structures

Vestibular portion
Cochlear portion
Nervus Intermedius
Labyrinthine artery
Internal auditory Canal
Common Disorders
- Acoustic neuroma
- Microvascular compression

Brainstem structures

Cochlear nucleus
Vestibular nuclei
Commisures
Cerebellar connections
Disorders
- Multiple sclerosis
- Stroke
  - AICA syndrome
  - PICA syndrome (Wallenberg's syndrome)

Ascending connections

Trapezoid body
- Because of cross-connections, central hearing loss is unusual and subtle
Inferior colliculus
- Little is known about effects of lesions
Medial Geniculate
- Little is known about lesions

Auditory and vestibular cortex