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