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BAHA (bone anchored hearing aid) -- BAHA, Ponto, Sophono

Timothy C. Hain, M.D. Bulent Mamikoglu, M.D.

Page last modified: August 31, 2017 See also: implantable hearing aids (but we think these are a bad idea). Cochlear implants and conventional hearing aids

Match between hearing and solutions
Hearing problem Options
Bilateral deafness Strong hearing aids, Cochlear implant
Unilateral deafness BAHA type device, CROS hearing aid
Partial hearing loss -- PTA > 35 Hearing aid, implantable hearing aid, assistive device
Minimal hearing loss -- PTA <35 Just turn up the volume. Usually hearing aid is not a good idea.

 

Terminology

We are mainly using the term BAHA to mean Bone Anchored Hearing Aid. The term "BAHA" is also the brand name of a specific device.

There are actually three brands of "BAHAs"

The image of the BAHA above, from Prosper hospital, shows how a button (or stud if you prefer) is inserted into the bone of the skull above the ear.

 

Ponto device Sophono
The BAHA device is attached to the button within the skull. It is unobtrusive (once the hair is put back into place). (image is from Island Hearing. ) The PONTO device is attached to an abutment (i.e. stud) behind the ear (image is from Ponto web site. ) The SOPHONO device is attached using a magnet (image is from Sophono web site. )

A BAHA device from Cochlear is shown above on the left. While a BAHA can be used like a conventional hearing aid, usually it is used in people who have good hearing on one side and no hearing on the other -- thus it is a surgically implanted version of the CROS aid. Most people with unilateral hearing loss are enthusiastic about BAHA aids because it works very well and it is unobtrusive. Faber et al (2015) reported that 83% of users were satisfied. It requires "very good" hearing on the opposite side. It eliminates the head shadow effect, occlusion effect, and feedback.

The Ponto hearing implant (upper middle) is a similar device that competes directly with the BAHA. It uses a somewhat different coupler that allows it to be angled (slightly), and it also has many programmable features. There are two models - -the Ponto Plus and Ponto Plus Power. The "Power" model can provide 55 dB of amplification, while the non-power model 45 dB -- similar to the Sophono device. Again, it works up to about 8K, but it has a little better high frequency response than the Sophono. This device is not going to have anywhere close to the Apple Iphone sound quality.

The Sophono device (upper right) is designed so that the bone implant is not visible, and the device is held onto the implant using magnets. The Sophono device provides about 45 dB of amplification at 2K. There is almost no amplification at 8K -- thus this device performs best at speech frequencies, but does not produce a "full spectrum" of sound. Or in other words, this device is not even close to the Apple Iphones sound quality. In essence, the Sophono device is a less capable device than either the Baha or the Ponto, but it is without the "stud", making it cosmetically preferable as well as requiring less skin care to prevent infection.

The main alterative to these devices is the "CROS" hearing aid. This is essentially a microphone sitting on one ear, and a speaker in the other.

There are also some devices called "active implants". These devices are technologically more advanced than the passive devices above. Most of them are not yet available in the United states.

Clinical indications:

There are two types of patients who might be candidates for these devices -- those with complete unilateral deafness (single side deafness -- SSD), and those with a more complicated situation with perhaps a mixed hearing loss on one side, or SSD on one side, and some kind of hearing loss on the other. To figure out which device might work one can just "try it out" using a simulator, or reason it out, based on ones knowledge of how these devices work.

The BAHA is most suitable for someone with a profound unilateral hearing loss (PTA > 90DB, WR < 20%). The other ear should have normal hearing.

The Sophono type of BAHA is most suitable for persons with less severe hearing loss -- best < 35 dB. Medtronic suggests that for use in single sided deaf patients, hearing should be normal (i.e. < 20 dB). The Sophono is not as powerful as the Ponto Plus, and also does not have as good frequency response. It is a choice for someone who is more concerned about their appearance.

BAHAs can also be used as a substitute for a hearing aid or stapes surgery on an ear with a conductive hearing loss. They are less risky than stapes surgery, and probably more durable. The big disadvantage compared to stapes surgery, though, is that they are cosmetically not nearly as good. All of these devices are visible and they all need batteries and maintenance.

These devices, like hearing aids, are beneficial for tinnitus. (Indeyeva et al, 2015)

According to Siau et al (2016), patients who might benefit from these types of devices decline due to anxiety (30%), cosmetic reasons (45%), lack of benefit (27%), and some just preferred conventional hearing aids (10%).

How BAHA devices are implanted.

For the classic "BAHA" device, first, a titanium stud (called a fixture or an abutment) is placed in the bone behind the ear, during a surgical procedure that typically takes only an hour (Garwecki et al, 2016). One then waits for 3 months until the titanium and bone heal together. After this, the sound processor is clipped onto the stud (it can come easily on and off). The Ponto process is similar.

The BAHA device also has an option where there is no stud -- called the "Attract system". Surgery is still needed, but the connection between the outside sound-processor and inside speaker system is through the skin using magnetic fields rather than a direct connection into the bone. The linkage involves adding more parts to the outer BAHA processor -- a magnet in particular.

This has an obvious cosmetic advantage in that there is no metal poking out through the skin behind one's ear. It is also less prone to develop infection. There are also of course many possible disadvantages -- the device might fall off as it is being held on by a magnet, the connection is not as "solid" as with the clip-on system, and we would also think that there could be fluctuations in how well it works depending on hair getting in the way, skin irritation, and perhaps some variability in device positioning. So until we encounter a few more of these, we suggest caution. The older device works very well.

The Ponto device is essentially a BAHA type device with updated software. According to Wazen et al, it can be "loaded" in 3 weeks, which compares favorably with the BAHA loading in 3 months (2016).

The Sophono device process is similar to the magnetic version of the BAHA. A magnet is implanted, and after it heals, then the Sophono is added and programmed. However, the Sophono has some disadvantages concerning sound quality as it is not as powerful and does not have as good a frequency response. According to Nelissen et al (2016) who compared BAHA and Sophono, "Tolerability was favorable for the Sophono. Aided thresholds with the Sophono were unsatisfactory, as they did not reach under a mean pure tone average of 30 dB HL". In other words, the Sophono is not as powerful as the BAHA. This all makes sense -- one gets better performance with a direct connection as in the BAHA.

How it works.

The sound processor converts sound into vibration, which is then transmitted to the titanium stud or plates embedded in the skull over the "bad" ear. Sound is transmitted through the bone of the skull to the other ear. Patients perceive sounds as coming from the deaf ear. Both ears remain open and unencumbered-- unlike the situation of a CROS aid which requires something placed into the good ear.

Trying out of these devices in the office

A simulator or Ponto with a headband provides a quick way of telling if the BAHA will work for any individual patient. These look somewhat like headphones, but the sound is transmitted through the bone on the bad side.

In our clinic office in Chicago, we have a Ponto and a Sophono that the sales organizations were kind enough to allow us to use. We do not have a BAHA simulator, but this matters little as BAHA has nothing to offer that is not already present in the Ponto and Sophono.

Comparison studies.

Multi-institutional data show that the "BAHA" is superior to the CROS device for ease of communication, reverberation, background noise, and aversion to sound. Average patient satisfaction is 80%.

What it doesn't do: Sound localization

BAHA doesn't improve sound localization. In fact, it is hard to imagine how it could. People with normal hearing use timing differences between the ears to localize sound. This is not available in the BAHA because all sound ends up going to the good ear.

The BAHA is also a poor choice if one needs more volume in the "good" ear too (Syms and Hernandez, 2014). This is similar to the situation with the Ponto and the Sophono, but the Ponto does have a bit more power than the other two.

Risks and complications of the BAHA type devices.

The most common problem is skin overgrowth over the stud, there also can be problems with infections, loose fixture, bone exposure, fixture loss. House and Kutz reported that postoperative problems requiring intervention occurred in 12.8% of their patients (2007). Skin overgrowth occurred in 7.4%, occurring on average 12 months after the initial procedure. Implant extrusion occurred in 3.4% of patients. Wound infections occurred in about 1% of patients. Obviously, these problems would be less likely when the implant is completely under the skin (as in the situation of the Sophono), but at this writing (2015), we are not sure that this is a good idea.

One of the authors of this page, Dr. Mamikoglu, has implanted 30 patients with the BAHA/abutment since 2008. Revisions were done in 16%.

MRI's in patients with these devices.

The devices discussed here differ in how compatible they are with MRI scanners. The titanium stud of the classic "BAHA" device does not have any MRI issue, as it is not magnetic. For the BAHA version with a magnet, it is not compatible with an MRI. There are times when one may want an MRI.

According to the Sophono literature, the device is safe in MRI scanners as powerful as 3T. This is the strongest current clinical scanner.

Azadarmaki et al (2014) recently reviewed information on MRI safety for commonly used otologic implants. According to their article:

MRI safety of hearing devices that are not implanted into the inner ear:

Costs

These devices for unilateral deafness are often not covered by medical insurance policies or medicare/medicaid. The BAHA or Ponto devices may cost about $10,000 after one includes the cost of the device itself (usually more than $5000), and the surgical costs. Thus these devices typically can cost more than a "Cros" hearing aid, which is the main alternative technology. They do offer advantages -- higher performance in some cases, a less obvious device that cannot be easily detected by others, and less "hassle".

Overall

The BAHA and related systems are a significant advance in the treatment of persons with single sided hearing loss. The BAHA is the oldest device. The Ponto is an updated version of the BAHA. The Sophono is different, possibly a little safer, because there is no "stud" behind the ear but it does not have as high performance as the BAHA and Ponto.

For complete unilateral hearing loss, we think it would be best to choose a strong device -- our pick would be the Ponto, as it is a little smaller and has more software options.

The Sophono seems to us the best choice for partial hearing loss because it is cosmetically the best, and because it is MRI compatable. On the other hand, why not use a conventional hearing aid if you are in this group ?

References:

 

Copyright August 31, 2017 , Timothy C. Hain, M.D. All rights reserved. Last saved on August 31, 2017