Tympanometry

What does tympanometry measure?

Clinical applications of tympanometry measurements are the identification of: 

• Middle ear effusion (Otitis media) 
• Perforation or cicatrisation of the ear drum
• Ear grommets
• Eustachian tube dysfunction
• Tympanosclerosis
• Otosclerosis
• Cholesteatoma

What is a tympanogram?

When the eardrum is activated by a sound wave, part of the sound is absorbed and sent through the middle ear, while the other part of the sound wave is reflected.

A tympanogram is a graphic representation of how the eardrum moves in response to the air pressure in the ear canal when performing tympanometry. The following data is obtained from tympanogram:

• Compliance with the middle ear system
• Ear canal volume
• Middle ear pressure
• Pattern correlated with various disorders

What is a tympanometer?

A tympanometer is an instrument that measures the pathology of the middle ear, including the ear drum. It is often referred to as a middle ear analyser, impedance or admittance meter, as the so-called tympanometry measurement is only one part of the entire middle ear assessment. Further tests include measurement of the interaural muscles (acoustic reflex, decay and latency tests) as well as eustachian tube tests. 

What is tympanometry?

First developed in the 1950's, tympanometry is an objective measurement used to evaluate the condition of the middle ear eardrum and the conduction bones by creating variations of air pressure in the ear canal (¹Terkildsen et al.). Since then, the test technique has further developed and become a common part of the audiological test routine.

¹Terkildsen, K. and K.A. Thomsen (1959). The influence of pressure variations on the impedance measuring bridge for clinical use. J. Laryngol. Otol. 73, 409-418.

What is an acoustic reflex measurement?

Just like tympanometry measurements, a probe is inserted into the ear canal. While playing a continues probe tone, short test signals (e.g. 0.5, 1 or 2kHz) are presented at levels of 70 - 100dB, triggering the stapes muscle to contract.

Through this contraction, the ossicular chain and ear drum stiffens as well, leading to a measurable decrease of compliance in the ear canal. The acoustic reflex is measurable in both ears (ipsilateral and contralateral).

Why measure acoustic reflexes?

Acoustic reflexes are regularly used in audiological testing and measure the stapedius and the tensor tympani reflex generated eardrum movement in response to intense sound. Acoustic reflex measurements provide feedback on:

• Type and degree of hearing loss (conductive, sensory, neural)
• Injury of the facial nerve or vestibulocochlear nerve
• Otosclerosis