Reflex Decay Testing

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Answer

It is interesting that you ask about the Acoustic Reflex Decay Test. In 1970, it was felt that acoustic reflex decay was common in the presence of acoustic tumors. However, later research showed that in fact the acoustic reflex will more likely be absent or entirely normal rather than decay when a tumor is present. Therefore you must first ask yourself why you are doing the procedure. If there is a strong suspicion of the presence of an acoustic tumor, then ABR would be the diagnostic procedure of choice.

The Acoustic Reflex Decay test is given with the stimulus presented in the ear contralateral to the probe tip. A continuous pure tone stimulus is presented 10 dB above acoustic reflex threshold for 10 seconds. Be careful, you must use good clinical judgment when presenting acoustic stimulation at intense levels, and you should not use stimuli that are above 105 dB HL or 115 dB SPL. The test is positive if the magnitude of the reflex decreases by more than 50% in ten seconds. In a normal ear, the reflex should stay contracted for the full 10 seconds. You are testing the ear which received the stimulus (not the probe ear). This concept tends to trouble many of my students. When eliciting the Acoustic Reflex you must first ask what you are trying to measure. If you want to determine presence or absence of the reflex then the test ear is the ear with the probe tip. However if you are making dynamic measures of the acoustic reflex such as threshold, latency or decay, then the test ear is the one with the stimulus. It all depends on the question you are asking; presence/absence is not the same question as threshold or decay - two different questions; two different ears.

Dr. Gerald T. Church has been educating audiologists for many, many years. He is a professor and Director of the Au.D. Program at Central Michigan University. He is currently an "empty nester" who is living the part of the story that begins "happily ever after" with his wife of 29 years in the wonderful town of Mt. Pleasant, Michigan. He may be reached at churc1g@cmich.edu.