Objective audiometry

From greek.doctor
  • Objective audiometry
    • Doesn’t depend on cooperation and subjective responses of patient
  • Otoacoustic emissions
    • Vibrations of hair cells in cochlea are transmitted back through the conducting apparatus
    • Test can only be performed if the middle ear function is normal
    • A microphone in the ear canal can detect otoacoustic emissions
    • Test reflects functional integrity of cochlea
    • Indications
      • Screening for cochlear function in newborns
        • Cochlear lesions are the major cause of hearing loss in this population
    • Two types
      • Spontaneous otoacoustic emissions
        • Spontaneous, without external stimulus
      • Evoked otoacoustic emissions
        • Stimulated externally
        • Transient evoked OAEs
          • Brief stimulus
        • Distortion product OAEs
          • Two continuous stimuli which distort each other
  • Brainstem evoked response audiometry
    • EEG above mastoid detects the activity of the auditory brainstem response in response to short stimuli
      • Five characteristic waves are seen on the averaged EEG
    • Infants must be sleeping or sedated
    • Indications
      • Determine auditory threshold objectively
      • Intraoperative monitoring
      • Differentiate cochlear and retrocochlear hearing loss‎