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AUD spring 2020 CI > Week 13 ABI > Flashcards

Week 13 ABI Flashcards

1
Q

what is the most successful sensory prosthetic device developed

A
  • cochlear implants

- –but they are not for everybody

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2
Q

what pts do not benefit from CIs

A
  • neurofibromatosis Type II
  • severed cochlear nerve from temporal bone fracture
  • congenital cochlear nerve aplasia
  • cochlear nerve
  • severe or complete cochlear ossification
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3
Q

the very first ABI

A
  • performed in 1979 at the House Ear Institute for a patient with NFII
  • –was a pair of ball-electrodes placed at the cochlear nucleus
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4
Q

what is NFII

A
  • autosomal dominant–chromosome 22
  • 1 and 40,000 births
  • generally lose all hearing by their 20-30 due to tumors and surgeries
  • –during surgery, the VIII nerve will usually be sacrificed
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5
Q

first multichannel ABI

A
  • house ear institute and cochlear inc collaborated to crease the first multichannel ABI
  • –it had 8 electrodes
  • created in 1991
  • FDA trials in 1994
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6
Q

how does an ABI function

A
  • electrode contacts of the implant are housed on a layer of silicone that resembles a paddle
  • two components
  • –external sound processor
  • –auditory brainstem implant
  • electrode array is placed over the cochlear nucleus
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7
Q

current approved ABI devices in the US

A
  • all from cochlear
  • –ABI24M (2000) compatible with N6
  • –ABI541 (2017) thinner and compatible wiht N7
  • —–both have 21 electrodes and removable magnet
  • —–mesh (net-like) to facilitate fibrous tissue growth
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8
Q

other ABI devices not yet approved in the US

A
  • Med-el Concerto ABI

* Oticon diagnostic SP ABI

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9
Q

ABI candidacy criteria in the US

A
  • over 12 yrs old
  • english speaking
  • bilateral vestibular schwannoma
  • highly motivated
  • reasonable expectations
  • psychologically stable
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10
Q

ABI candidacy criteria outside the US

A
  • bilateral vestibular schwannoma
  • severe cochlear malformation
  • severe ossification
  • severe auditory neuropathy
  • cochlear nerve avulsion
  • cochlear nerve aplasia
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11
Q

ABI surgery basics

A
  • ABI is placed following the first removal of the tumor
  • want to give pt some hearing experience before they lose their hearing completely
  • preserve anatomical structures through avoiding any distortions
  • in case the implant is unsuccessful, implanting the contra side is an option
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12
Q

what is the placement goal of an ABI surgery

A

place the electrode at the dorsolateral surface of the cochlear nucleus– this will give less non-auditory stimulations

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13
Q

retrosigmoid approach to ABI surgery

A
  • enhances the chance of preserving residual hearing
  • poor visualization of the facial nerve, and requires retraction of the cerebellum
  • –this manipulation of the cerebellum is dangerous
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14
Q

translabyrinthine approach to ABI surgery

A
  • only FDA approved procedure
  • direct access to the floor of the fourth ventricle and surface of the cochlear nucleus
  • minimal cerebellar retraction
  • easier identification of the facial nerve
  • removal of tumor from the internal auditory canal
  • lower rate of morbidity
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15
Q

3 major complications of ABI implantation

A
  • CSF leak
  • implant migration
  • non-auditory stimulation
  • –most commonly–vertigo and tingling
  • –jitter of the visual field
  • –muscle twitches
  • –ipsilateral tingling
  • non auditory stimulations improve with longer stimulus duration, slower rate, and with time (however 9% could persist)
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16
Q

activation of ABI

A
  • about 6 weeks post op and over a 3 day period
  • during activation it is more likely to elicit a non-auditory stimulus from an ABI compared to a CI
  • –vagus nerve stimulation
  • –bradycardia
  • –motor tract stimulation: tingling sensation may occur throughout the ipsi side of the body
  • –vertigo
  • –throat tightening
  • –fainting
  • cardiac monitoring and physician attendance and active role of the programming audiologist
  • any electrode that causes these non-auditory stimulations should be turned off
  • because the cochlear nucleus tonotopic organization is much more complicated than the cochlea we use
  • –pitch scaling with ranking from 1 (low) to 100 (high) and have them rate sharpness
  • –pitch ranking is comparing 2 electrodes
  • loudness balancing at he USL
  • unlikely for excellent speech rec, so do closed set SRT and warble tone testing
  • follow up every 3 months for a year, then annually
17
Q

ABI outcomes

A
  • outcomes are widely variable (individual based)
  • –on average, 81% of patients receive auditory stimulation
  • —–similar to the outcome of single channel CI
  • –improved detection/discrimination of environmental sounds
  • –improved lip-reading
  • —–improved ability to understand speech by an average of 26% compared to the visual only
  • —–however average open-set speech recognition score less than 10% correct
  • ——–some pts had up t 60% on open-set sentences or up to 100% in some cases of cochlear nerve aplasia
  • –better performance in non NFII
18
Q

who is not an option for benefit from vestibular implant

A
  • acute unilateral–not a consolidate
  • –vestibular neuritis, trauma, labyrinthitis
  • –potentially could recover
  • potentially successful compensation
  • recurrent unilateral–but really depends on the condition
  • –challenge of recurrent/episodic issues is there is not opportunity for compensation
  • –BPPV–definitely not a candidate
  • –meniere’s disease
  • —–causes imbalanced output from the vestib system so theoretically it could help suppressing the attack before it starts if it functions like a vestibular pacemaker
19
Q

who might benefit from a vestibular implant

A
  • chronic unilateral
  • –not for compensated cases
  • –appropriate when the brain fails to compensate–for example after vestibular neuronitis
  • recurrent bilateral are candidates
  • –bilateral meniere’s disease for example
  • chronic bilateral are candidates
  • –ototoxicity
  • –presbystasis
  • –idiopathc bilateral loss
20
Q

sensor-based design of vestibular implant

A
  • replaces the function of the damaged sensory organ
  • monitor sensor (angular gyroscope and linear accelerators) which sends info to a signal processor which sends info to a nerve stimulator which sends info to the VIII nerve
  • good for chronic unilateral and bilateral conditions
21
Q

pacemaker-based design of vestibular implant

A
  • no motion sensors but instead a preprogrammed algorithm to replace the missing tonic activity from vestibular afferents to increase VOR gain
  • recurrent vertigo (menieres disease)
  • –during the vertigo attack the device is turned on so there is a signal processor sending info to the nerve stimulator which stimulates the 8th nerve
  • with an uncompensated system the device stays on so the signal processor sends signal to the nerve stimulator which stimulates the 8th nerve
22
Q

first vestibular implant prototype

A
  • merfeld and gong at massachusetts eye and ear infirmary
  • –this is the first prototype described which was in 2000
  • –was a sensor-based implant (gyroscope) and had a single electrode
  • –demonstrated the VOR was partially restores in monkeys and guinea pigs
23
Q

nucleus freedom vestibular implant system

A
  • developed by cochlear and rubinstein et al at the university of washington (seattle, WA)
  • it is a pacemaker-based implant
  • developed with external nulti-axis gyroscope that connects to an osseointegrated abutment
  • –trigurcating electrode array with 9 total electrodes
  • trial on monkeys
  • approved for feasibility trial in humans
  • –golub et al (2014) 56 yr old male wit unilateral menieres
  • —–were able to stimulate eye movement with each canal
  • —–could not preserve vestibular and hearing function
24
Q

multichannel vestibular implant (MVP 1,2)

A
  • developed by della santina et al (2005) at johns hopkins
  • device developed by labyrinth devices LLC in collaboration with Med-El
  • MVP2– one single axis and one dual axis gyroscope, and a tri-axis linear accelorometer
  • contains 3 electrodes
  • –anterior and horizontal canals
  • –posterior canal
25
Q

multichannel vestibular prosthesis (MVP1, 2)

A
  • developed by della santina et al (2005) at johns hopkins
  • device developed by labyrinth devices LLC in collaboration with Med-El
  • multichannel vestibular implant (MVI)
  • –human trial–FDA approved it as investigational device (2016-2020)
  • —–60 participants recruited, 15 were qualified and implanted
  • ——–22-90 yrs old with bilat vestibular loss and good hearing in at least 1 ear
  • ——–bilateral loss because of ototoxicity, blood flow loss to inner ear, trauma, infection
  • ——–exclusions: CI, active MD< immunodeficieny disease, or other surgical contraindications
  • ——–results based on 4 subjects (ototoxicity) show restoration of VOR after 2.5 yrs of stimuations

AUD spring 2020 CI (16 decks)

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