Implantables Midterm Flashcards
(121 cards)
What are middle ear implants (MEI)?
surgically implanted component that is coupled to a structure in the ME and that mechanically oscillates to facilitate stimulation of the cochlea
What are the theoretical advantages of MEI?
greater gain, improved comfort, higher fidelity sound, not needing as much gain due to the nature of the implants, aesthetic appeal and good for patients who want continuous wear
What are the theoretical disadvantages of MEI?
surgical procedure, cost is high as insurance does not often cover the devices, hearing implications as a result of disarticulation potentially needing to occur, not MRI compatible beyond 1.5 T and there are troubles with verification as there is no acoustical output to measure within the canal
are patients with conductive HL candidates for MEI?
they were not originally included within the MEI candidacy however some patients may be considered as a candidate if their ME is aerated and free of chronic effusion
-additionally, some implants can be coupled to the round window therefore avoiding the ossicles so could be beneficial for otosclerosis
what assessments do we conduct for potential MEI patients?
-air and bone thresholds at 250 to 8000 Hz
-evaluation of ME function through tymps, reflexes and wideband reflectance
-trial with conventional HAs
-real ear probe microphone measurements to ensure optimal HA output
-aided WRS at levels consistent with daily listening situations (both at 60-65 and 50 dB SPL)
-medical evaluation by an otologist, including a CT scan or even an MRI to assess CNS
what is the audiological management with MEI?
-activation occurs weeks after surgery
-devices are programmed using software given by the manufacturer
-verification relies on behavioral and functional measures (including sound field threshold, aided WRS, Quick-SIN, and questionnaires)
what are the 3 types of transducers that are used with MEI?
piezoelectric, electromagnetic, and electromechanical
what is a piezoelectric transducer, and how does it work?
this transducer possesses a unique property, as when they come in contact with electricity,y they oscillate
-when they are coupled to the ME, the material delivers mechanical energy, converting sound-induced vibrations into electrical signals for processing
-the intensity and frequency generated are proportional to the intensity and frequency of the driving force
what are the advantages of a piezoelectric transducers?
there is no external power source required, and they have relatively robust durability
what are the limitations/disadvantages of a piezoelectric transducers?
may not provide enough amplification due to limited output and a narrow bandwidth
what is an electromagnetic transducer, and how does it work?
this transducer features a biocompatible magnetic coupled to the ossicular chain or ME structure and is positioned near a wired coil within the canal
-as an electrical current goes through the coil, it generates a fluctuating magnetic field, causing the magnet to oscillate and transfer mechanical energy to the ossicular chain
-the magnet moving along with the ossicle,s giving a back-and-forth movement between the magnet/coil
what are the limitations/disadvantages of an electromagnetic transducers?
the output depends on the magnet-coil proximity
-decreasing with longer distance
-with this type of transducer, since the magnet is on the ossicular chain and the wire is in the canal, the fluctuations that occur depend on the proximity
why was the electromechanical transducer designed?
this transducer was designed to eliminate the limitation of distance with electromagnetic transducers
-the coil and magnet are within one unit, ensuring mechanical energy transfer to the coupled structure within the ossicles
what are the advantages of an electromechanical transducers?
delivers higher output levels/wider frequency response and is not impacted by variable output due to changes in magnet coil distance
what are the limitations/disadvantages of an electromechanical transducers?
complex design and is more prone to mechanical failure
what are the three MEI devices offered today?
vibrant sound bridge, maxum (ototronix), envoy esteem
tell me about the vibrant sound bridge MEI
a partially implanted MEI that contains both an external sound processor and the internal soundbridge implant
-sound is captured by the microphone, then is analyzed and converted to an electrical current
-this is then transmitted through electromagnetic induction and is altered back to the electrical signal and once it is received by the FMT the ossicular chain is set into motion
what is the FMT within the vibrant soundbridge?
the floating mass transducer which is attached to the ossicular chain and receives the electrical current
tell me about the maxum (ototronix) MEI?
a partially implanted device with the external integrated processor and the iron magnet
-the IPC is placed within the canal and the magnet is housed somewhere on the ossicles
-when the IPC receives the sound, it becomes amplified and converted to an electrical current
-this current crosses the TM as an electromagnetic signal and goes towards the magnet
-this causes the implant to vibrate, and therefore the ossicles vibrate
tell me about the envoy esteem MEI?
a fully implantable device that has all component combined into one device
-the sensor, containing piezoelectric transducer, converts the movement of the incus to an electrical signal that is delivered to the sound processor
-it then reaches the driver, and is then converted to mechanical oscillations causing the stapes to vibrate
what are the general FDA indications for MEIs?
-18 years +
-SNHL in the moderate to severe range
-WRS greater then 40-60% (depends on manufacturer)
-normal ME anatomy/function
-experience with appropriately fit HAs
-ABGs no larger than 10 dB
what are the general contraindications for MEI?
-conductive HL
-retrocochlear or central auditory disorders
-active or history of recurrent ME infections
-TM perforations
-disabling tinnitus
-any skin or scalp conditions/sensitivities
what are bone conduction hearing devices?
HA that amplifies sound through bone conduction, serving as an alternative to a regular HA for those with problems in their outer or middle ears
what are the basic components of bone conduction devices? what is the job of each?
-external sound processor, captures the signal and converts it to mechanical vibrations, delivering those vibrations to the internal components
-titanium component which is surgically implanted in the skull and uses those mechanical vibrations to the cochlea through bone conduction
-abutment, sits on the fixture holding it into place