Hearing loss

• Conductive hearing loss
  • Impaired conduction of sound through outer ear, tympanic membrane or middle ear
  • Children and young adults
  • Etiology
    • Tympanic membrane perforation
    • Otitis media with effusion
    • Barotrauma
    • Otosclerosis
  • Diagnosis
    • Pure tone audiometry
      • Auditory threshold increased for air conduction
      • Auditory threshold normal for bone conduction
    • Speech audiometry
      • Increasing loudness eventually leads to 100% speech comprehension
    • Rinne test
      • Unable to hear tuning fork after moving it from mastoid to outer ear
• Sensorineural hearing loss
  • Lesion of cochlea, vestibulocochlear nerve or central auditory pathways
  • Adults and elderly
  • Etiology
    • Congenital
    • Acquired
      • Presbycusis (aging) (most common cause)
        • Especially high frequencies
      • Ototoxicity
      • Meniere disease
      • Acoustic neuroma
      • Noise-induced hearing loss
      • Trauma
      • Otitis interna
      • Diabetic otopathy
  • Diagnosis
    • Pure tone audiometry
      • Auditory threshold increased for both air and bone conduction
    • Speech audiometry
      • Increasing loudness never leads to 100% speech comprehension
• Combined hearing loss
  • Diagnosis
    • Pure tone
      • Auditory threshold is increased for both air and bone conduction, but it is increased more for air conduction
• Tuning fork tests
  • Distinguish conductive and SNHL
  • Weber test
    • Tests for lateralization (sound is louder in one ear)
    • Base of tuning fork on the middle of forehead – bone conduction to cochlea
    • Interpretation
      • Lateralization to one ear = contralateral sensorineural HL or ipsilateral conductive HL
      • No lateralization = normal hearing or bilateral HL
  • Rinne test
    • Tests for air conduction and bone conduction
    • Base of tuning fork on the mastoid process
      • -> which side is louder?
      • -> when the patient no longer hears the tone, move front of the fork to the outer ear and ask if the patient still hears it
        • Air conduction is greater than bone, so patient should still hear the fork
    • Interpretation
      • Sound is louder with air than bone conduction (positive Rinne) = no conductive HL in examined ear
      • Sound is louder with bone than with air conduction (negative Rinne) = conductive HL in examined ear

• Noise-induced hearing loss
  • Excessive noise causes direct mechanical and metabolic injury
  • Types
    • Acute acoustic trauma
      • < 1,5 ms sound of >140 dB
      • Gunshot, airbags, fireworks
    • Blast injury
      • Pressure wave ruptures tympanic membrane
    • Acute noise-induced hearing loss
      • Seconds – hours
      • Jet engine, concerts, power tools
      • Often reversible
    • Chronic noise-induced hearing loss
      • Chronic exposure to loud sounds
      • Loud music, party
  • Clinical features
    • Muffled sensation
    • Tinnitus
  • Diagnosis
    • Hearing threshold decreased at all frequencies, especially 3 – 6 kHz‎