Middle Ear Implants Flashcards
What are the different types of devices?
Acoustic to acoustic (conventional hearing aids)
Acoustic to mechanical vibration (ME implant, bone conduction hearing devices)
Acoustic to electric (cochlear implant, brainstem implant)
What are middle ear implants?
A surgically implanted component that is coupled to a structure in the ME and that mechanically oscillates to facilitate stimulation of the cochlea
What experiment played a pivotal role in ME implant development?
Wilska’s experiment in 1935
Placed iron particles on the TM and using an electromagnetic coil inside an earphone
Demonstrated the generation of a magnetic field that caused the iron particles to vibrate
This vibration was then transmitted to the TM, facilitating sound transmission to the inner ear
Was progress in ME implants limited from 1935 to 1959?
Yes, until Rutschmann’s work in 1959
Documented the stimulation of the ossicles using alternating magnetic fields on a magnet attached to the TM
Did further advancements in ME implants occur in the 1970s?
Yes, this marked the introduction of surgically implantable devices for the ME
Who made the first working ME implant system?
G.R. Ball
Did limitations in the available hearing aid technology lead to the emergence of MEI hearing devices in the 1990s and early 2000s?
Yes, it was presented as a solution to overcome these limitations, particularly in addressing high-frequency hearing loss
What are some limitations of conventional hearing aids?
Placement loss
Social stigma
Discomfort
Maintenance
Occlusion
Feedback
Wax problems
Poor sound quality
Distortion
Insufficient gain
What was the first MEI hearing device that received FDA approval for commercial use?
Symphonix Vibrant Soundbridge in 2000
What were the two components of the Symphonix Vibrant Soundbridge?
An external sound processor with a microphone that captured sound, processed it digitally, and transmitted it to an external coil via electromagnetic induction
An internal coil which processed the signal and delivered it to a vibrating mechanical component that was coupled to the ossicular chain
What are the theoretical advantages of MEI?
Greater gain (increased gain prior to acoustic feedback, although some feedback risk remains due to enhanced mechanical oscillation)
Avoidance of the occlusion effect (crucial for individuals with external otitis or skin allergies, unaffected by cerumen-related problems; some MEI require the use of a component in the external auditory meatus)
Improved comfort (especially with fully implanted options)
Higher-fidelity sound (sound with less distortion compared to air conduction aids)
Aesthetic appeal (especially if the components are implanted under the skin)
Continuous wear (fully implanted devices allow 24/7 wear during daily activities, including showering and sleeping)
What are the theoretical disadvantages of MEIs?
Surgical procedure (required 1-2 hours under general anesthesia with risks like facial nerve injury and infection; complication rates are generally low)
Cost and insurance (higher costs compared to traditional aids, not typically covered by health insurance)
Hearing implications (some devices involve disarticulation of the ossicular chain, resulting in max conductive hearing loss when inactive)
MRI compatibility (most devices contain magnets, prohibiting MRI without implant removal; some exceptions with Med-El Vibrant Soundbridge)
Verification challenges (don’t produce acoustic output in the ear canal, making traditional REM measurements unfeasible for verifying the appropriateness of gain/output)
What are FDA approved indications for MEI?
18+ years old with SNHL
Moderate to moderately severe hearing loss with reasonably good open-set word recognition capacity (>60%) in optimal conditions
Individuals with lower WRS scores may not experience significant improvement in hearing performance with MEI
Hearing loss should ideally be stable
Normal ME anatomy and function without infection
Prior experience with hearing aids
*Off-label recommendations may be made when medically justified, regardless of FDA approved indications
Are patients with CHL considered to be poor candidates for MEI?
Yes, especially in the cases of chronic middle ear effusion
Some adults may be considered for MEI if the middle ear is aerated and free of chronic effusion or cholesteatoma
Some MEIs can bypass the ossicles by coupling the oscillating transducer to the round window, offering direct stimulation of the cochlea (ideal for conditions like otosclerosis or other ossicular chain pathologies)
What is done during the pre-op assessment for MEI?
Air and bone conduction pure tone audiometry at octave and interoctave frequencies (250 to 8000 Hz)
Evaluation of ME function (tymps, acoustic reflexes, and wideband reflectance)
A trial with conventional air-conduction hearing aids
Real ear probe tube measurements to ensure optimal hearing aid output matches evidence based prescriptive targets
Aided word recognition assessment at speech levels consistent with speech encountered in daily listening activities (60-65 dB SPL and 50 dB SPL)
Thorough medical evaluation by otologist to meet criteria for MEI consideration (includes CT scan to assess ME anatomy and surgical planning)
Some otologists may order a pre-op MRI to assess the CNS due to complications with MRI interpretation after MEI surgery
Are audiologists responsible for activation and monitoring of MEI?
Yes
Device activation occurs weeks post-surgery
Audiologists should conduct otoscopy at each session to monitor the implant site for signs of inflammation or discomfort
How are MEI programmed?
Using proprietary software and tools provided by the manufacturer
How are MEI verified?
No standardized verification exists, standard real ear measures are not applicable
Verification relies on behavioral and functional assessments to ensure that recipients receive adequate benefit (sound field detection thresholds for warbled tones, aided monosyllabic word recognition in the sound field at a presentation of 50 or 60 dBA, sentence recognition in noise such as the QuickSIN, and standardized questionnaires like the APHAB or the COSI)
Are the number of recipients of MEI available?
No, but numbers are expected to be lower than those for CIs, largely due to differences in insurance coverage
Are the theoretical benefits claimed by early developers of MEI still evident today?
No
Advances in digital hearing aid technology have addressed many of the limitations that existed almost 20 years ago and have allowed for satisfactory hearing performance for most persons with mild to severe SNHL
Advances in CI and hybrid technology, along with expanded criteria, allowed individuals who are unable to achieve satisfactory performance with conventional hearing aids to consider CI as an alternative
Why do we still use MEI?
A typical recipient is one who strongly prefers a totally implantable (or partially) hearing devices for cosmetic or lifestyle reasons
Fit - discomfort, otitis external, occlusion effect, poor retention
Use - limited vision, dexterity, self-efficacy, lost devices, frequent battery changes
Lifestyle - removal for sleep, water wear, athletic endeavors with heavy perspiration
They may be medically necessary for persons who tolerate the presence of a hearing aid in or on the external ear (external otitis, excessive cerumen, etc.)
Although rare, it may be the ideal solution for those unsatisfied with the performance obtained with air-conduction hearing aids and does not have enough loss to warrant CI
What are the clinical outcomes for MEI?
Studies show that they provide better hearing than unaided conditions
Performance in speech recognition (quiet and noise) and aided thresholds is typically comparable to conventional air conduction hearing aids
Many users report high satisfaction and functional benefit even if audiometric outcomes are similar to conventional aids
What are the different types of transducers for MEI?
Piezoelectric
Electromagnetic
Electromechanical
What is piezoelectric?
These materials possess a unique property when they come in contact with electricity (they oscillate when subjected to electricity and generate electrical voltage when physically displaced)
When coupled to the ME, these materials deliver mechanical energy, converting sound-induced vibrations into electrical signals for processing
The intensity and frequency of an electrical signal generated by piezoelectric material is essentially proportional to the intensity and frequency of the driving force
No external power source is required and they have relatively robust stability and durability
They may not provide enough amplification for those with moderate to sever hearing loss due to their limited output and narrow bandwidth
What is electromagnetic?
Features a biocompatible magnet coupled to the ossicular chain or ME structure, positioned near a wire coil
Electrical current through the coil generates a fluctuating magnetic field, causing the magnet to oscillate and transfer mechanical energy to the ossicular chain
Magnet movement intensity and frequency correspond to the electrical currents characteristics
Output of electromagnetic transducers depends on magnet-coil proximity, with output decreasing by the square of the distance between them (surgeons must position the coil and magnet at recommended distances to ensure optimal performance)
Head and mouth movement may temporarily alert their proximity, affecting magnet output momentarily
What is electromechanical?
A variant of electromagnet transducers and were designed to eliminate the limitation that occurred when a suboptimal distance existed between the coil and the magnet
Magnet and coil are housed together, eliminating issues related to variable distances
Design optimizes and stabilizes spatial separation, ensuring efficient mechanical energy transfer to the coupled structure
Deliver higher output levels and wider frequency responses compared to electromagnetic transducers
Not affected by variable output changes due to changes in magnet-coil distance
More complex design and more prone to mechanical failure but modern manufacturing practices minimize the risk of mechanical failure, making this drawback negligible
What are the modern MEI devices?
Partially implantable (Vibrant Soundbridge, maxum)
Totally implantable (envoy esteem)
What is the Vibrant Soundbridge?
Med-El device
Is partially implantable that contains two basic components (an external sound processor known as SAMBA 2 audio processor and the med-el vibrant soudbridge implant)
What are the components to the vibrating ossicular prosthesis (VORP 502x) implant?
Used in some vibrant implants (vibrant HF, vibrant D, and vibrant soundbridge)
A receiving coil that surrounds a biocompatible magnet (electromechanical)
An internal processor and stimulator (the demodulator)
A lead (the conductor link) that delivers electrical current from the stimulator to the transducers
Floating mass transducer (FMT)
Where is the FMT coupled in the soundbridge?
Typically coupled to the long process of the incus, this amplified mechanical energy for greater ossicular chain and cochlear displacement
Alternatively, it may be coupled to the incus body
For recipients with mixed/conductive hearing loss, it may be coupled to the round window from direct cochlear stimulation
How does the vibrant soundbridge work?
Sound captured by the sound processor microphone is analyzed by its digital processor
The processed signal is converted to electrical current and transmitted via electromagnetic induction through the processor transmitting coil
The VORP 502x coil receives the signal and converts it to an electrical signal that is delivered to the implant processor for analysis
Electrical current travels down the conductor link lead to the FMT, and electrical transducers with a wire coil surrounding a magnet housed in titanium
The current through the coil creates a magnetic field, oscillating the magnet within the FMT
What are the FDA-approved indications for use for the Med-El Vibrant Soundbridge?
Adults (18+)
Audiometric results consistent with SNHL
Unaided pure tone air conduction thresholds within the following ranges:
500 Hz - 30 to 65 dB HL
1000 Hz - 40 to 75 dB HL
1500 Hz - 45 to 80 dB HL
2000 Hz - 45 to 80 dB HL
3000 Hz - 50 to 85 dB HL
4000 Hz - 50 to 85 dB HL
WRS of greater than or equal to 50% correct at 65 dB SPL
Normal ME anatomy
Psychologically and motivationally suitable with realistic expectations of the benefits and limitations of the device
What are the contraindications for the Med-El Vibrant Soundbridge?
CHL
Retrocochlear or central auditory disorder
Active ME infections
Tympanic membrane perforations associated with recurrent ME infections
A skin or scalp condition that may preclude attachment of the audio processor
Will the vibration be proportional to the same intensity of the incoming signal?
Yes
What does FMT stand for?
Floating mass transducers
Is the FMT attached to the long process of the incus for SNHL?
Yes, that is the most common placement
Have there been multiple soundbridge audio processors?
Yes, the eternal processor is often updated and users can replace the processor without replacing the implanted components
AP404 (2003)
Amade (2009)
Samba (2015)
Samba 2 (2020)
*don’t need to know the specifics of previous devices
What are some features that the samba 2 processor has?
Intelligent sound adapter 2.0
Noise reduction
Adaptive directional microphone technology and speech tracking
Bluetooth
Noise cancellation
Wind noise reduction
What are the components to the Ototronix Maxum MEI?
An externally worn ear-level sound processor known as the Integrated Processor and Coil (IPC) and consists of an in-the-canal style hearing aid that contains a microphone, digital sound processor, and an electromagnetic coil that is attached to the medial end of the device
A neodymium-iron-boron magnet that is housed in a titanium case
*electromagnetic processor
How does the Ototronix Maxum MEI work?
The IPC houses both the sound processor and the electromagnetic coil
The IPC receives sound, amplifies it, and converts the signal to an electrical current that is delivered to the electromagnetic coil at the tip of the device
As the electrical current travels through the coil, it is converted to an electromagnetic signal that emanates across the TM and toward the Maxum’s magnet, which is coupled to the incudostapedial joint at the neck of the stapes
This could changes the sounds to electromagnetic signals, which causes the implant to vibrate
What are the FDA-approved indications for the Ototronix Maxum MEI?
Adults (18+)
Audiological results consistent with moderate to severe SNHL
Experience with an appropriately fitting hearing aid
ABG no more than 10 dB
Preoperative WRS should be equal to or greater than 60%
What are the contraindications for the Ototonix Maxum MEI?
CHL
Retrocochlear or central auditory disorder
Active ME infections
TM perforations associated with recurrent middle ear infections
Disabling tinnitus
What is the Envoy Esteem?
The only FDA-approved fully implantable MEI
The implant is typically activated about 6 to 8 weeks after surgery
What are the components of the Envoy Esteem?
Sensor
Sound processor
Driver
Non-rechargeable lithium-iodide battery
*all of these components are contained within one implantable devices implanted in the temporal bone
Is there a battery inside the device on the Ototonix Maxum MEI?
Yes, it lasts a few years and then they need to have surgery again once it dies
How does the Envoy Esteem work?
Sound processor and battery are implanted in a “bed” that the surgeon hollows out in the temporal bone just behind the auricle
Sensor and driver (extensions off the sound processor) are placed in the middle ear space
The Esteem sensor is couples to the body of the incus and contains a piezoelectric transducer that converts the movement of the incus into an electrical signal which is delivered via a lead to the Esteem sound processor
The Esteem sound processor analyzes the signal, which is then transmitted through a separate lead to the esteem driver
The Esteem driver houses a piezoelectric transducer, which converts the electrical signal into mechanical oscillations (driver attached to the stapes)
*The surgeon needs to disarticulate the incus and the stapes so they don’t both convert to electricity (so the driver is not effected by the movement of the sensor)
How is the surgery done for the Ototonix Maxum MEI?
Can be done under local anesthetic of the TM
Lift the TM and place the processor on the incus-stapedial joint and then replace the TM
Is the surgery of the sound bridge invasive?
Yes because they need to drill the bone
What are the FDA-approved indications for the Envoy Esteem?
Adults (18+)
Stable bilateral SNHL
Moderate to severe SNHL defined by PTA
Unaided speech discrimination test score greater than or equal to 40%
Normally functioning eustachian tube
Normal ME anatomy
Adequate space for the Esteem implant as determined by high-resolution CT scans
A minimum of 30 days of experience with appropriately fit hearing aids
ABGs of no more than 10 dB
Pre-op WRS of 60% or greater
What is important to remember about piezoelectric?
If you apply vibration, electricity is produced
If you apply electricity, vibration is produced
No external energy source needed
Does the processor have batteries in the Envoy Esteem?
Yes, that means it needs to be replaced every 4 to 10 years
What are some contraindications for the Envoy Esteem?
History of post-adolescent chronic ME infections, inner ear disorders, or recurrent vertigo requiring treatment, disorders such as mastoiditis, hydrops, or menieres
Known history of fluctuating air conduction and/or bone conduction hearing losses over the past year of 15 dB in either direction at two or more frequencies
History of otitis external or eczema of the EAM
Cholesteatoma or destructive ME disease
Retrocochlear or central auditory disorder
Disabling tinnitus
History of keloid formation
Hypersensitivity to silicone rubber, polyurethane, stainless steel, titanium, and/or gold
Pre-existing medical condition or undergoing treatment that may affect the healing process
Pregnancy
What are some disadvantages with the Envoy Esteem?
Not MRI compatible, so the device should not be considered for persons who must undergo serial MRI assessment
Typical cost associated with implantation is about $35,000 to $40,000 per ear (health insurance doesn’t typically cover the costs)
How is the Envoy Esteem programmed?
Done by the audiologist and is tricky
No way to verify the fitting
Recipient is seen multiple times over the first few months of device use for programming to optimize hearing performance, which usually reaches optimal levels four to six months after surgery
