This test is to determine the problems in the middle Ear due to middle ear Pathology and Eustachian Tube dysfunction (ETF Test). Tympanometry is a test of the middle ear function and the eardrum. It provides valuable information on the condition of the middle ear and assesses the mobility of the eardrum by varying the air pressure in the ear canal. Prior to tympanometry testing, it is important to do an otoscopy to ensure that the ear canal is cleared from impacted earwax and fluid.
The test helps to: -
* Assess the eardrum movement (compliance)
* Monitor chronic middle ear fluid
* Confirm tympanic membrane perforation
* Monitor Eustachian tube function
It is an objective test it only takes a few minutes and can be easily performed on patients of all ages. The test is performed by inserting the tympanometry probe in the ear canal which generates a pure-tone signal and measures the sound reflected from the eardrum at different pressures. The waveform is called a Tympanogram. It is important to note that Tympanometry is NOT a hearing test. It does not assess the sensitivity of hearing and the results of this test should be viewed together with Puretone Audiometry. The result of the test helps to distinguish between sensorineural and conductive hearing loss especially middle ear conditions such as otitis media with effusion, otosclerosis, cholesteatoma, tympanic membrane scarring, tympanosclerosis, etc. The Tympanogram can be broadly classified into 3 types.
Stapedius reflex measurements provide information about the middle and inner ear, in addition to the eighth and seventh nerve (proximal to the innervation of stapedius) and brainstem function. Dynamic changes which result from contraction of stapedius in response to stimuli of 500, 1000, 2000, and 4000 Hz, at intensities of 70–115 dB sound pressure level, are measured and thresholds for activation are documented.
The stapedius reflex can be measured both ipsilaterally and contralaterally. Stapedius reflex thresholds arise from stimulation across the four frequencies 500, 1000, 2000, and 4000 Hz and are measured both Ipsi and contralaterally, and threshold abnormalities are identified according to the criteria below (Cohen and Prasher, 1992)
1. > 15 dB difference at two adjacent frequencies when compared to the opposite ear
2. > 115 dB.
Measurement of stapedius reflex thresholds can also identify loudness recruitment, one of the hallmarks of cochlear impairment. The objective finding is an abnormal growth of response with sound level. Typically the stapedius reflex is triggered by sound levels 60 dB louder than the hearing threshold. Thus, when the hearing thresholds are raised and yet the stapedius reflex is recruited at only 30–40 dB above, recruitment is identified.
Abnormal stapedius reflex decay
The full tension of the stapedius muscle cannot be maintained in response to continued stimulation. The tension drops to about 50% of its maximum value after a few seconds. Abnormal decay of the stapedius reflex is an indication of eighth-nerve abnormalities.
Eustachian Tube Function Test: