Auditory mechanism

1
Auditory mechanism

• Outer ear
• Middle ear
• Inner ear

2
Outer Ear

• Auricle or pinna
• External auditory meatus

3
Middle Ear

• Tympanic membrane
• Ossicular chain
• Malleus, incus, stapes
• Eustachian tube
• Oval window

4
Inner Ear

• Cochlea
• Basilar membrane
• Organ of Corti
• Semicircular canals vestibular function
• Cranial nerve VIII vestibulocochlear nerve

5
Hearing impairment

• Conductive loss
• Sensorineural loss
• Mixed

6
Conductive hearing loss

• Pathology located within the outer or middle ear
• Slight, mild or moderate degree of loss
• Often can be surgically or pharmacologically
  corrected
• Flat audiogram
• e.g. otosclerosis

7
Sensorineural loss

• Damage to inner ear or cranial nerve
• Slight, mild, moderate, severe or profound loss
• Degree of loss varies by frequency
• Not easily corrected through surgery
• e.g. presbycusis

8
Mixed

• Simultaneous presence of sensori-neural and
  conductive hearing loss
• 75 year old man with presbycusis and impacted
  cerumen