Title: 6.1 Lesson Five Lecture & Reading Assignment
Course: 14SU-HIS-230-GH101-ADVANCED AUDIOMETRY > Section: Lessons

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Lesson Five Lecture

Tympanometry

Reading Assignment:

Martin, Introduction to Audiology- Chapter 7.  There is other information in this chapter you are welcome to read but focus on the section regarding tympanograms and acoustic reflexes.

This week our new information is on the topic of Immittance or Impedance audiometry.  You will see both terms used.  What does it mean?  While you will need to understand what is being measured and how we will be using the more common terms: tympanometry (or a tympanogram) and acoustic reflexes to describe the tests we are doing.  The tympanogram is a test of middle ear function.  Acoustic reflexes give us information about the auditory pathways all the way up to the brain.  Both tests can be used in addition to the tests you have learned about up to this point to help determine the type of hearing loss and what is called the “site of lesion”.  We will focus on the tympanogram and ipsilateral acoustic reflexes.

Some of you may be wondering if you need to do these tests as a hearing instrument specialist.  Those of you who are working in clinics or talking to individuals who are already licensed may or may not see these testing being done as a part of the test battery for fitting hearing instruments.  As a HIS (hearing instrument specialist) these tests can help you identify the type of hearing loss and if a referral is needed.  Fitting individuals with hearing instruments that have a medical condition that can be treated or who may have something more serious going on and need medical intervention is a serious matter.  I would like to be able to tell you I have never seen it happen; unfortunately that is not the case.  However because you are in this program you will have a much better foundation in your knowledge about hearing loss types, when to refer and who has the potential to be successful with hearing instruments.

The tympanogram measures how efficiently the middle ear is working.  Don’t let all the terms make you nervous.  It seems like a lot to learn but we will focus on the important concepts and terms.  When you do tympanometry you are really completing four tests:

1. The tympanogram- The graph used to plot middle ear function is called a tympanogram.  There are five main categories for the results: A, A_D A_S, B & C.
2. Static Compliance- This is the height of the tympanogram at its peak.
3. Physical Volume of the ear canal- The volume of the ear canal is measured.  There is a typical volume for a normal adult ear or child’s ear.
4. Acoustic Reflexes- These can be ipsilateral or contralateral.  We will focus on ipsilateral.  An acoustic reflex is the involuntary contraction of the stapedius muscle in the middle ear.

Let’s go through each of the test above to help you pull all of the information from the reading and powerpoints together:

1. Tympanogram results-  These will be calorized into five basic types: Type A- normal; Type A_D- the peak or static compliance is high;Type A_S- the peak or static compliance is low;Type B or flat- the ear drum has little or no movement; Type C or negative pressure- there is significant negative pressure in the middle ear.
2. Static Compliance-  This is the peak of the tympanogram.  There will be a peak in all of the above tympanogram types except Type B.
3. Physical Volume of the ear canal- As part of the test the volume of the ear canal can be measured.  A small volume and a Type B tympanogram indicates the probe tip is up against the ear canal wall.
4. Acoustic reflexes- These measure crossed and uncrossed neural pathways.  They are always reported according to the ear that got the stimulus and in Sensation Level.  Focus on how the ipsilateral reflexes are obtained and what they mean if they are present, at a reduced sensation level or absent.

How do these tests help me when I am concerned about the tests I need to properly fit hearing instruments?  There are several situations where these tests can help you make an appropriate referral and help you understand the test results you are getting for a particular individual.  You will see sample audiometric results with tympanometry in Dr. Venema’s ppt presentation to help you visualize this.  Some potential situations are:

1. Sloping sensorineural HL, no air/bone gap.  Normal tympanogram (type A) and acoustic reflexes are present.  There is no medical pathology going on with this client.  You can proceed with recommending amplification.
2. Flat or sloping HL, air/bone gap.  Shallow tympanogram (type A_S), absent reflexes.  If the air/bone gap is 15dB or more at 500, 1000 and 2000Hz you should refer.  There are several conditions that could cause this.  This person might be cleared for hearing instruments but must have a medical evaluation first.
3. Flat HL, air/bone gap.  Flat tympanogram (type B) or negative pressure (type C).   These results indicate some sort of middle ear pathology and should be referred.  Many times with these results hearing will return to normal after medical intervention.

These are only examples to get you thinking.  As you get to practice these tests in the lab you will begin to understand more completely how to use them and to interpret the results.  In the reading and the powerpoints focus on the basics of how these tests are done and what they mean.

Attached Files: | - Lesson Five Lecture.docx