What does Hearing Preservation Mean?

A 1997 House Ear Institute study reported 68% success in preserving hearing using the middle fossa approach...

We've all seen statistics like the one above. Here is another study:

Combined, this represents a hearing preservation rate of 87% after surgical treatment of Grade II acoustic neurinomas.

Does this mean what we think it does? Most patients would assume that "hearing preservation" means that your hearing after surgery is at least as good as before. It does not; it just means that you are not completely deaf, that a useable amount of hearing is still left. Here is an example:

Hearing was preserved in 24 patients; 17 were available for testing for the present study... All patients maintained usable hearing.

Useable, or useful hearing does not mean that you can hear the telephone or understand conversation. A patient can lost almost all their hearing and still be considered to have hearing preservation, as long as there is enough left so can be useful in some situations, such being able to hear a fire alarm go off.

Though "usability" is the most common criterion for when hearing is considered "preserved", some studies define it more precisely, such as:

speech reception threshold < 50 dB, speech discrimination score > 60%;

Here is an example from another study:

50-dB pure tone average and 50% speech discrimination score.

But no study ever uses ther term "hearing preservation" with the meaning that we would expect it to have, i.e. that your hearing is preserved as is.  [And here is more bad news:  if your speech discrimination is affected, hearing aids will not bring it back.  Speech discrimination problems are due to damaged hearing nerves, and amplifying the volume does not help.]

A natural question to ask is:

given the true meaning of "hearing preservation", just what % of surgery patients are having their hearing REALLY preserved, at the pre-surgery level?

Unfortunately, surgeons do not report what % of the patients in their studies preserved their hearing at or above pre-surgery levels; it would not look as good as the "hearing preservation" statistic they use now. We wish they did. That way, we'd be able to compare their results with those reported for radiosurgery, where preservation of hearing at the original level or better ("hearing-level preservation") is always reported, such as in this quote from a study:

for 75% of FSR patients, hearing had not worsened

We are also wondering: if all patients were told up-front just what the words "hearing preservation" mean, would people opt to risk their facial nerves, their balance, or their headache-free and fatigue-free existence, just so as to increase their chance of preserving their hearing?

Last Edited: Friday, November 01, 2002