Middle Ear Implant: An Audiologist's First Hand Experience

In September 1998, I made the decision to become a subject in the clinical trials for the Symphonix Vibrant Soundbridge middle ear implantable hearing aid. It is without a doubt the best decision I have ever made concerning my hearing health.

I was born with a mild sloping to moderately-severe bilateral sensorineural hearing loss, with my right ear being slightly poorer than my left ear. I have been a hearing aid user for many years, and overall, my experience with hearing aids was very positive.

As an audiologist, I had available to me the latest technology and I did not experience the frustration of being overwhelmed by environmental noise which affects so many of our patients.

Why did I choose the implantable hearing aid? My greatest frustration with
hearing aids was the discomfort I experienced due to the sensitivity of the skin in my external auditory canals. Despite the use of hypoallergenic shell material, the frequent removal of my hearing aids in order to perform listening checks caused constant irritation.

In July 1998, I received information from the University of Miami regarding candidacy for cochlear implantation. Almost as an aside, candidacy criteria for participation in the Vibrant Soundbridge middle ear implant clinical trials was included in the mailing. I met all the criteria and I contacted the University of Miami for more information. After undergoing an extensive battery of tests, and meeting with the implant surgeon, I was informed that I was accepted into the study. Surgery was scheduled for early September 1998. My right ear was selected to receive the implant.

The surgery was performed under general anesthesia and took approximately three hours. The implanted components include; an ''internal receiver'' placed under the temporalis muscle behind the ear, the ''conductor link'' is placed within the mastoid bone, and the ''floating mass transducer'' (FMT) which is attached to the incus using a titanium clamp. The implant transmits via electromagnetic transmission. Sounds are received and converted into electrical signals by an external audio processor and are transferred from the internal receiver to the FMT to enhance and amplify the natural movement of the ossicles.

I was released from the hospital the day following surgery. Postoperatively, I experienced dizziness for the first five days and moderate discomfort and headaches for the first week. Ten days post-op I was back at work. To date, I have had no chronic, or long-term post-operative surgical complications.

In early November 1998, eight weeks following surgery, I was fit with the audio processor. It was an amazing experience. It was raining very hard that day. I rode home in the car with my eyes closed just listening to the sound of the rain as it hit the windshield. Though not an unfamiliar sound, it was clear and almost melodic to me. I also noticed that I could comfortably hear my radio with the volume set to my husbands comfort level, despite the sound of the rain and the car engine! Best of all, I can wear the implant during all of my waking hours. Something I was never able to do with hearing aids.

The gain that the Vibrant Soundbrige provides is measured in the soundfield using warbled tones and various speech tests, including SRT, word recognition, and the SPIN test. All tests are performed with the contralateral ear occluded. Below are my unaided and aided results to warbled tones in the soundfield:



My aided SRT was 20dBHL and my aided word recognition score was 88% on an NU-6 word list presented at 55dBHL. I received a total word score of 289/312 on the SPIN test, which was presented at 55dBHL with 47dBHL of speech babble.

It has been nearly 20 months since I was implanted. I am currently wearing an 8-channel digital audio processor, although I stared with a two channel digitally programmable unit. I have experienced no major problems with any of the audio processors I have worn. I have been successful in all listening environments.

I have abandoned the hearing aid in my left ear because I find the differences in amplification more detrimental than beneficial. I do, however, carry both my conventional in-the-canal hearing aids with me as back up. Typically, I am much happier binaurally aided.

As an audiologist, the advice I offer other audiologists is not to view this as a threat to a successful dispensing practice. It is our responsibility to guide our patients through all options open to them to achieve better hearing. Audiologists are, and will continue to be the professional of choice to provide and program the audio processor.

Counseling patients with regard to implantable hearing aids is extremely important. Patients must understand the benefits and the limitations of implantable hearing aids, particularly with respect to traditional custom made hearing aids. The clinical knowledge and counseling ability of the audiologist is clearly critical in determining the best choice for each patient.

I believe the most successful implant wearer will be one who has achieved success acoustically with hearing aids. If a patient has not been able to adjust successfully to amplified sound, a successful fit with an implantable hearing aid is questionable.

Implantable hearing aids offer the ability to better amplify higher frequencies without feedback, and the ''occlusion effect'' is virtually non-existent.

However, the implant wearer goes through the same adaptation to amplified sound as hearing aid wearers. Implantable hearing aids will become a viable amplification option for hearing impaired persons and audiologists must rise to meet this remarkable technology and the challenges it presents.