Question
Can you please explain the advantages and disadvantages of transtympanic versus extratympanic electrocochleography testing?
Answer
I. Advantages of transtympanic approach:
1. Larger signal to noise ratio due to proxximity of primary electrode to response generators-produces large magnitude responses with little signal averaging.
2. Responses are very stable and repeatable.
3. Can measure responses in the face of moderate-severe hearing loss.
II. Disadvantages of transtympanic approach:
1. Invasive procedure, cannot be performed by audiologists
2. Painful for subjects.
3. Need for local/topical anesthetic
4. Cost to patient may be higher since procedure is invasive.
III. Advantages of extratympanic procedures (including tympanic membrane
approach)
1. Non-invasive, can be performed by audiologists.
2. Not painful if done correctly.
3. Patterns of abnormality leading to diagnostic interpretation preserved. 4. Cost to patient is less since procedure is non-invasive.
IV. Disadvantages of ET EcochG:
1. Need more signal averaging because electrode is more ''far-field'' (thus, test takes longer). Smaller component magnitudes.
2. Responses not as repeatable/stable.
3. Responses poorly defined/absent is the face of hearing loss greater than 50-60 dB HL in higher frequencies.
The above items have appeared in several of the articles that I have published on EcochG.
John A. Ferraro, Ph.D.
Professor and Chairman
Hearing and Speech Department
University of Kansas Medical Center
Co-Director
KU Intercampus Program in Communicative Disorders
Associate Dean for Research, School of Allied Health 913-588-5937
[email protected]
For more information, please read Clinical Electrocochleography: Overview of Theories, Techniques and Applications
John A. Ferraro, Ph.D.
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