Esteem - The first totally implantable hearing aid

One of the highlights of the  ISCON 2012 conference was the lecture by Prof Ricardo Bento, Sao Paulo,  Brazil about his experience with Esteem- the first totally implantable hearing aid.  Initially we wondered as  to  why one  would go through the trouble of going through a surgical procedure,  instead of just popping a very tiny concealed completely in the canal hearing aid into your ear canal and be done with it.  But after hearing Prof. Bento, we came to know as to some people will go through all the trouble. One of the famous implantees is none other than the renowned Otologist, Dr. Michael Glasscock.  Prof. Bento showed us the clippings of the procedure and I should say that it is not a easy surgery at all.  The FDA took all of five years to approve this implant.  He explained how using a conventional canal hearing aid cuts off the resonance created by  the external auditory canal,  before it strikes the tympanic membrane.  It is unique in that it is powered by a battery, which has a life from  about 3 to 9 years.  This device is  also powered by a piezo device which uses the vibration of the tympanic membrane to generate its charge.  Since it has no external parts, the user can swim or have a bath and still hear.  The device can be controlled with a remote control, and if you take the trouble to turn it off at night, the battery will last even longer.  The battery can be changed with a small incision under local anaesthesia.

 The Esteem® system includes three implantable components (Sound Processor, Sensor, and Driver), and external testing and programming instruments.  The Esteem Totally Implantable Hearing System by Envoy Medical Corporation (St. Paul, MN) is a fully implantable system that uses piezoelectric transducers.  It uses the eardrum as the microphone.  The mechanical signal is detected by a piezoelectric transducer at the head of the incus (the sensor) and converted to an electrical signal that is amplified, filtered, and converted back to a vibratory signal.  The processed vibratory signal is then delivered by another piezoelectric transducer (the driver) to the stapes capitulum.  The Esteem hearing implant is different from all other microphone-based hearing devices (e.g., hearing aids, other middle ear implants or cochlear implants) because it uses the eardrum to process the incoming sound and thus preserves a natural way of hearing.  The Esteem is implanted under the skin behind the ear and in the middle ear space, and therefore invisible.


https://www.youtube.com/watch?v=xdBzjR-i9E0
(How the Esteem works- Animation)

https://www.youtube.com/watch?v=XdKVaW8krOY
(Esteem testimonial-Dr.Glasscock)

The Esteem® device is intended to reduce the effect of moderate to severe hearing loss in patients 18 years of age or older. The Esteem® is used in patients with hearing loss that meet the following criteria:

• Stable hearing loss caused by defective hair cells in the inner ear (sensorineural loss) in both ears
• Moderate to severe sensorineural hearing loss as defined by Pure Tone Average (PTA) at 500, 100, and 2000 hertz (Hz)
• Ability to understand what is heard (speech discrimination test score) greater than or equal to 40% of the words heard during the test.
• Normally functioning middle ear (Eustachian) tube
• Normal middle ear anatomy
• Normal tympanic membrane
• Adequate space for the Esteem® implant determined through a high resolution Computed Tomography (CT) scan
• Minimum 30 days of experience with appropriately fitted hearing aids.

The Esteem® device should not be used under the following conditions: History of:

• post-adolescent chronic middle ear infections
• inner ear disorders or recurring vertigo requiring treatment
• disorders such as an infection of the mastoid bone (mastoiditis)
• swelling in the inner ear (hydrops)
• Meniere’s disease (a condition characterized by a ringing sound in the ear(s) or head [tinnitus], hearing loss, vertigo and a feeling of fullness in the ear)
• disabling tinnitus which requires treatment
• fluctuating air conduction and/or bone conduction hearing loss over the past one year period of 15 decibels (dB) in either direction at two or more hearing frequencies (from 500 to 4000 Hz)
• swimmer’s ear (otitis externa) or eczema of the outer ear canal
• destructive middle ear disease (cholesteatoma)
• central auditory disorders (retrocochlear)
• thick scar tissue that continues to grow (keloid formation)
• excessive sensitivity to silicone rubber, polyurethane, stainless steel, titanium and/or gold

A clinical study of this device involved 60 subjects at 3 investigational centers (57 were implanted with the device). The side-effects observed in the clinical study included:

• Taste disturbance: 42% of subjects (14% ongoing after 1 year)
• Facial paresis (partial paralysis) / paralysis: 7% of subjects (1% ongoing after 1 year)
• Tinnitus: 18% of subjects* (5% ongoing after 1 year) * Some subjects reported having tinnitus prior to the Esteem® implant.

The surgical procedure involved a wide mastoidectomy,  a posterior tympanotomy, resection of the long process  of the incus, and fixing the driver and the overall system within the middle ear cleft.  The tricky part is stripping off the entire mucosa from the stapes superstructure.  This is a very delicate maneuver and subluxation of the footplate could be a  disaster.  This stripping is essential in order to fix  the driver  to the stapes superstructure using cement.  Specific surgical training is needed to accommodate routine surgical steps along with less familiar steps, such as placement of cement material and overall fixation of the system.  

It is certain that these hearing aids are expensive and requires a lot of expertise in implanting them.  It will be preferred b y certain individuals like doctors, musicians and sports persons for whom wearing a conventional hearing aid could be a hindrance in their day to day lives.   It will be interesting to see  how popular these  type of hearing aids will become in the future.