1. Bone Anchored Hearing Aid or Cochlea Implant?
Timothy Alberg
Biomedical Engineering
University of Rhode Island

2. Index Hearing Loss Bone Anchored Hearing Aids (BAHA)
Cochlear Implants (CI)
Experiment 1
Experiment 2
Results

3. Hearing Loss 4 Types of Hearing Loss.
Conductive: Sound is not transmitted efficiently from the outer ear to the cochlea.
Sensorineural: Hearing loss due to damage to the cochlea or nerve endings in the inner ear.
Mixed: Combination of Conductive and Sensorineural hearing loss.
Unilateral hearing: Hearing in one ear, Hearing loss in the other.

4. Bone Anchored Hearing Aid
Hearing aid that uses bone conduction to transmit sound vibrations through the skull and to the cochlea.
Design includes a titanium implant, an external abutment that connects to the implant, and a sound processing device that connects to the abutment.
The sound processing device picks up external sounds and transmits them through the skull via the implant.
This bypasses the external ear canal, which allows users with conductive hearing loss to hear again.

5. Bone Anchored Hearing Aid

6. Cochlear Implant
Bone conducting hearing device that is used with patients who have extreme hearing loss.
External: Microphone to pick up sound
Sound Processor to make signals based on the sound.
Transmitter to send out signals from the sound processor.
Internal: Receiver to pick up the transmitted signals and convert them to electrical impulses.
Electrode Array to stimulate various portions of the cochlea nerve.

7. Cochlear Implant

8. Degrees of Hearing Loss

9. Experiments
Research was conducted to evaluate when it is appropriate to use a Bone Anchored Hearing Aid and when it is appropriate to use a Cochlear Implant for patients with mixed hearing loss.
Experiment 1 consisted of 5 patients who used the BAHA until progressive sensorineural hearing loss made it difficult to hear. They were then outfitted with cochlear implants and monitored for five years.
Experiment 2 consisted of 3 groups of patients: 1 group consisted of patients using the BAHA, another group consisted of patients with normal cochlea using CI, and the last group consisted of patients with otosclerosis using a CI.

10. Experiment 1 This experiment took about 10 years to complete.
All 5 patients had mixed hearing loss, otosclerosis (abnormal bone growth in the middle ear), or many known cases of Otitis media (bacterial infection of the inner ear).
The 5 patients were studied for five years with the BAHA, and 5 years with a CI.
The CI were fitted after the BAHA failed to provide the type of hearing assistance that the patients required.

11. Experiment 1 cont.
Speech and Phoneme tests were conducted to evaluate the degrees of hearing loss of each patient at a set sound pressure level of 65 dB.
The higher the % at a Sound Pressure Level of 65 dB, the better.
The lower the values for hearing loss, the better.
The test frequencies ranged from 0.5 to 2 KHz.

12. Experiment 1 cont.
Patient1: Had an aided threshold hearing loss of 40 dB with the BAHA and a sound pressure level score at 65dB (PS65) of 65% at the beginning of the experiment. Over the course of three years, the PS65 value dropped to 35% due to his otosclerosis.
He received a cochlear implant and more than two years later, he had an aided threshold hearing loss of 35dB with a PS65 of 62%.

13. More Experiment 1 results
Patient 5 suffered from otosclerosis of the left ear, and ear-aches from his air conductive hearing aids.
Before he was fitted with a BAHA, bone and air conduction audiometry tests showed significant hearing loss. 60 dB below 1kHz, and 70 dB above 1kHz.
After being fitted with a BAHA, however, the hearing loss was still 60dB and the PS65 value was less than 5%.
5 years after being fitted with a cochlear implant, audiometry tests showed improvement in his hearing. The hearing loss was 30 dB with a PS65 of 90%.

14. All Experiment 1 Results

15. Experiment 2
The BAHA group consisted of 27 patients with minimal sensorineural hearing loss.
The first CI group (CI1) consisted of 123 patients with normal cochlea.
The second CI group (CI2) consisted of 14 patients who have otosclerosis.
The test involved speech recognition at a sound pressure level of 65dB. Their score was based on recognition of 13 phonetically balanced words transmitted from a loud speaker 1 meter in front of them. The testing room was soundproof to prevent interference due to ambient noise.

16. Results of Experiment 2
The phoneme scores that the BAHA group achieved were almost completely dependent of the level of hearing loss that each patient had. This allowed a regression plot to be fitted to the data points.
The phoneme scores for CI1 and CI2 were independent of level of hearing loss, and so the results were plotted using a different method.
The researches took the mean score, and the tenth percentile score, and plotted those on the BAHA group plot. For CI1, the mean and 10th percentile scores were 74% and 42%. This means that 50% of CI1 scored higher than 74% on the phoneme test, and 90% of CI1 scored greater than 42% on the test. The results of CI2 for the mean and 10th percentile were 45% and 10%, which was significantly lower than the results for CI1.
From these results, the researchers decided that a suitable cut-off point for BAHA users to switch over to CI was scoring lower than 42% on a phoneme test at a sound pressure level of 65dB.

17. Experiment 2 Graph Results

18. More Experiment 2 Results
Another cut-off point between the BAHA and CI was decided by viewing where BAHA fitted plot crosses through the 10th percentile line for first cochlear implant group.
The point was somewhere between a hearing loss of 60 and 70 dB.
Thus from this experiment, two cut-off points could be used while determining if a patient should use a CI or switch from the BAHA over to a CI.
Once again, these two cut-off points are: Scoring bellow a 42 while using a hearing aid for a phoneme test at a sound pressure level of 65 dB, and having a hearing loss that is greater than 70dB.

19. Conclusion
Typically, cochlea implants cost more to fit to a patient and the surgery is more invasive than the surgery required to fasten the bone anchored hearing aid to the skull.
The cost for a CI ranges from 50,000 to 100,000 USSD.
The cost for a BAHA is around 40,000 USSD for the device and surgery.
However, despite the extra cost and surgery, it is highly recommended to use a CI if either of the cut-off points are met, due to the potential benefits, especially for those with progressive hearing loss.
The patients from experiment 1 have been monitored for more than 6 years after the CI, and have not suffered any detrimental side effects.
The BAHA seems more effective for patients who suffer from conductive hearing loss.
For those who have mixed or progressive sensorineural hearing loss, the CI is the better choice.
Choosing the right hearing aid saves the patient a lot of expenses, and this research directly benefits the patient in that way.
The bionic ear that works for all types of hearing loss is still a long ways away, but being able to determine which types of cochlea stimulation work best for each type of hearing loss is the first step down that road.

20. Work Cited
Verhaegen. MD, Veronique J. O., Jef J. S. Mulder, MD. PhD, Emmanuel A. M. Mylanus, MD, PhD, Cor W. R. J. Cremers, MD. PhD, and AdF.M. Snik,PhD. "Profound Mixed Hearing Loss: Bone-Anchored Hearing Aid System or Cochlear Implant?." Annals of Otology, Rhinology & Laryngology (2009): Print.
Wikipedia contributors. "Bone Anchored Hearing Aid." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 20 Jan Web. 28 Jan
Wikipedia contributors. "Otitis media." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 28 Jan Web. 30 Jan
"Bone Anchored Hearing Device." UCIrvine Health Sciences University of California, Irvine , Web. 30 Jan <
"Cochlear Implants." National Institution of Deafness and other Communication Disorders. Aug National Institute of Health, Web. 29 Jan <
"Costs Associated with Cochlear Implants." Cochlear Implant Center University of Miami School of Medicine, Web. 31 Jan < ith%20Cochlear%20Implants.asp>.

21. Work Cited cont.
"Otosclerosis." National Institution of Deafness and other Communication Disorders. May National Institute of Health, Web. 30 Jan <
"Type, Degree, and Configuration of Hearing Loss." American-Speach-Language- Hearing Association American-Speach-Language-Hearing Association, Web. 31 Jan <
Courtesy of the plots is from:
Verhaegen. MD, Veronique J. O., Jef J. S. Mulder, MD. PhD, Emmanuel A. M. Mylanus, MD, PhD, Cor W. R. J. Cremers, MD. PhD, and AdF.M. Snik,PhD. "Profound Mixed Hearing Loss: Bone-Anchored Hearing Aid System or Cochlear Implant?." Annals of Otology, Rhinology & Laryngology (2009): Print.
Photo for degrees of hearing loss courtesy of: