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- 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
- 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
