The primary purpose of impedance audiometry is to determine the status of the middle ear and mobility of the tympanic membrane and conduction of sounds by ossicles.
It also assesses the acoustic reflex pathways including the auditory brainstem & cranial nerves 7th & 8th. This test cannot be used to directly assess auditory sensitivity, although results are interpreted in conjunction with auditory threshold measures.
Acoustic immittance is a measurement of energy or air pressure flow, which involves the ear canal, ear drum, ossicular chain, tensor tympani, stapedius muscle, cochlea, cranial nerves 7th and 8th and the brainstem. Mass, mobility, and resistance of outer and middle ear systems affects this test. The reciprocal of acoustic impedance is acoustic admittance. Particularly in earlier years, these measurements were perfomed in impedance rather than immitance measures, thus impedance audiometry is sometimes used.
Impedance audiometry mainly includes tympanometry, thresholds of acoustic reflex, reflex decay & eustacian tube function. They help in determining the functioning of central auditory system & determine conditions like eustacian tube dysfunction, tympanic membrane hypermobility, tympanosclerosis, otosclerosis, M. E. effusion, ossicular discontinuity, facial nerve function, hearing loss as well as brainstem disorders.
What is the normal value of Impedance Audiometry
When this test used?
To determine middle ear dysfunction.