Asymmetric SP/AP Ratios

Question

Answer

What a great question. Although this column is entitled "Ask the Expert", I'm not an expert in ECochG . However as director of an Au.D. degree program, I know who to go to for an answer. I would like to thank Dr. Dawn Nelson who helped me answer this question.

If the assumption is made that you are using an ear canal electrode or a tymptrode and not a trans-tympanic electrode, then you are correct that a SP/AP ratio that is less than 50% is considered normal. Although the two ears are quite different in your question, it does not matter in this case. These results are still normal. There are a number of measurement and patient variables that may account for this large difference. Your question illustrates the importance of properly collected and statistically validated normative data. I had an old statistics professor once tell me that statistical conclusions are a lot like pregnancy. They are either significant or non-significant. There is no such thing as "almost" significant. No one can be "almost" pregnant either.

Dr. Gerald T. Church has been professor and director of the on-campus Au.D. program at Central Michigan University since it's inception in 1994. His quiet life as an "empty nester" has recently been thrown into turmoil with the planning of the wedding of his oldest of three daughters. He may be reached at churc1g@cmich.edu