Sunday, November 14, 2010

Audiology Report from Buffalo Children's

I received the official audiology report from Buffalo Children's audiology department. I am impressed it arrived so quickly! It states that Nolan has a moderately severe mixed hearing loss, has patent PE tubes (i.e. his middle ear ventilation tubes are working very well), and that he is an absolutely amazing kiddo. But we already knew that.

Since my friends/family are probably addled by all the charts, I'm going to explain Nolan's results- so my hearing loss bloggy friends can stop reading now. I'm pretty sure all of you are all too familiar with audiograms! Also, this will be boring. Fair warning.

For those not as familiar with an audiogram, it is a graph displaying "frequency" across the top. Frequency is pitch- it is like a piano keyboard rolled out in front of you. Middle C is at 250Hz, which is the lowest useful frequency used for human speech. 8000Hz is very high pitched- think of a shrill whistle (or the higher pitched sounds like "s" and "th").

The volume is placed down the side of the audiogram. It is recorded in decibels (dB)- children with normal hearing can hear from 0-15dB (adults with normal hearing can detect sounds from 0-25dB). A whisper is at about 30dB, conversational speech is at 55-60dB, and jackhammers are around 100dB.

I have placed Nolan's hearing levels onto an audiogram which has the sounds of speech placed onto it. Nolan's right ear is red, and his left ear is blue. He cannot hear any sounds above the lines. In other words, he hears almost no speech sounds without his hearing aids. He can hear shouting, dogs barking, and other loud sounds.

Audiologists like to know what is causing the hearing loss, so they test both the inner ear (how well the delicate hair cells in the cochlea are working) and the middle ear (the mechanical portion of hearing). The middle ear bones vibrate and transmit sound to the inner ear, and the inner ear hair cells move and transmit the sound information to the auditory nerve. If either system is "broken," sound will not get through to the brain. Problems with the middle ear are generally correctable, if the problem is caused by middle ear fluid or a malformed middle ear bone. Problems with the inner ear are not correctable.

A problem with the mechanical, middle ear function is called a "conductive hearing loss." A problem with the inner ear is called a "sensorineural hearing loss." Conductive hearing losses are treated with surgery to correct the problem, or hearing aids if the problem is not correctable. Sensorineural hearing losses can only be treated with hearing aids (or cochlear implants for severe-profound levels of hearing loss).

They test the "middle ear system" by placing a vibrating sound system on the head, called a bone oscillator. This sends sound directly to the inner ear (cochlea) and bypasses the middle ear. If there is a problem in the middle ear, this type of testing will show the true hearing ability of the inner ear.

They tested Nolan's middle and inner ear systems, and found the following:

The black line shows that when they bypass Nolan's middle ear system, he hears better than when they play sounds through headphones. This means that a portion of his hearing loss is due to a mechanical problem with his middle ear bones. The other part is due to inner ear hair cell damage.

This type of hearing loss is termed a "mixed hearing loss." In Nolan's case, nothing can be done to fix the conductive portion, since we don't have a cause for it. His mechanical problems are not caused by fluid, since he has functional tubes in his eardrums. It is likely that his mechanical sound transmission problems are caused by stiffened middle ear bones- the result of chronic infection. This is why ENT's are very aggressive in treating middle ear infections in children with pre-existing hearing loss. Even though our ENT has been right on top of Nolan's hearing loss and ear infections, damage has been incurred. Hopefully the new, spiffy "permanent" tubes will prevent further damage to his middle ear system.

In the meantime, Nolan has yet another cold with a fever- hopefully this will disappear in time for his pH probe on Monday. I am ready for summer to arrive and these nasty germs to disappear!


Herding Grasshoppers said...


thanks for the great explanation. You're a natural teacher! Even we moms of HoH kiddos like things explained in layman's terms :D

Hope Nolan's well for the ph probe,


Joey @ Big Teeth and Clouds said...

We're getting to that horrible time of year when everyone is coughing and fevering. Surely those tubes will be tested. I hope they cure the problem!