Impedance Audiometry

Impedance is total opposition by a system to the flow of energy. Impedance audiometry is an objective procedure which assesses tympanic membrane mobility, pressure in the middle ear, and stapedial reflexes.

This test contains two procedures

Tympanometry

It is a test of tympanic membrane mobility. It measures the energy transmission through the middle ear. A tympanogram is a graphical representation of middle ear compliance under changing pressure conditions. 226Hz probe tone is usually used to assess tympanic membrane mobility.

Acoustic Reflexes

Acoustic reflex testing assess the neural pathway. This is measured in response to loud sounds of 70-90 dB above thresholds. They are of two types Ipsilateral and Contralateral. It uses the auditory nerve (VIII cranial nerve) as an afferent pathway and the facial nerve (VII crainal nerve) as an efferent pathway.

Indications-

  • To identify Tympanic Membrane Movement (Normal, Stiff or Flaccid)
  • To identify patency of Eustachian Tube
  • To Identify Ossicular Chain Fixation, Continuity & Discontinuity
  • To identify Middle Ear Fluid
  • To identify Malingering of hearing loss
  • To assess facial nerve integrity