FAQ- What is usable hearing?

[Mark]

The question of defining serviceable hearing levels gets asked quite often. For those that are curious I saw a response from Dr. Medberry on the CPSG board which I thought might help explain it. He is responding to a specific post so I'll include that for the sake of context, but the defintion of the different grades is the important part. I didn't recognize the poster as someone who has been on this board, but if it is I'll apologize in advance for borrowing it 

Patient

I am 25 years old, and in good health. I have been diagnosed with an acoustic neuroma in my right ear. I have off and on ringing in that ear, and occassional dizziness that lasts for a few minutes. My hearing is normal, and my last audiogram showed the hearing in the right ear was slightly better than the left ear. My tumor is 1.2cm x 0.8cm x 0.6cm. Previously, it was 0.8 x 0.8 x 0.6. I have now had three MRIs. The second MRI (0.8 x 0.8 x 0.6) showed no growth, but the most recent one showed growth.

My doctor is advising me to continue waiting until I lose some hearing before getting any treatment, as any treatment (he recommends gamma knife, but we have never talked about cyber knife) presents a risk of hearing loss, and he says that most patients he has treated show an average of 10% hearing loss, though some lose all hearing in the treated ear. I am having trouble finding information about hearing preservation and do not understand what useful hearing means. If anyone can clarify, that would be great. Also, I realize that neuromas are not all that common for someone my age, but if anyone can advise as to whether continuing to watch and wait for a patient with a growing tumor and normal hearing is common advice, that would be great as well.

Thanks.


Dr. Medberry

Different clinicians may give you different advice, but I would advise treatment. If this grows sufficiently large, then it will certainly cause hearing loss. I can see little justification for waiting until you have some hearing loss since you already know it is growing and the eventual outcome is virtually certain. THe choice between CK and GK is a little more difficult. Ck can offer fractionated treatment. Some data suggests that this may be better at preserving hearing, but the issue is far from certain. The Pittsburgh group reports 60-70% hearing preservation with Gamma Knife. Rates as high as 93% have been reported with fractionated CK treatment. As for the definition of serviceable or useful hearing, there are various definitions. THe most commonly used is the Gardner-Robertson scale:
Class I Excellent 0-30 dB hearing loss 70-100% speech discrimination
Class II Serviceable 31-50 dB hearing loss 50-69% speech discrimination
(can use telephone)
Class III Non-serviceable 51-90 dB hearing loss 5-49% speech discrimination
Class IV Poor 91-max dB hearing loss 1-4% speech discrimination
Class V None Not testable 0

Most writers consider Class I and II to be efsuul or serviceable, but occasionally you will see papers which inexplicably include Class III as having serviceable hearing.

Clinton A. Medbery, III, M.D.
St. Anthony Hospital Cyberknife Center

[FlyersFan68]

According to the chart it seems that whoever cannot understand speech while using the telephone has non-serviceable hearing at the very least. It always seemed to me that audiologic evaluatons can be somehwat difficult to understand. One may do somewhat well in the hearing booth and scores may refelct somewhat optimistic results but in the real world that same person could totally be unable to carry a conversation or use the telephone on the affected side. If the other ear was affected in the same way having class 3  levels then that person in reality would not understand general conversaion or use the telephone at all having the "Charlie Brown" effect constantly. Good to have this scale posted here.