Week 13 ABI Flashcards
1
Q
what is the most successful sensory prosthetic device developed
A
- cochlear implants
- –but they are not for everybody
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
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
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
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
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
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
8
Q
other ABI devices not yet approved in the US
A
- Med-el Concerto ABI
* Oticon diagnostic SP ABI
9
Q
ABI candidacy criteria in the US
A
- over 12 yrs old
- english speaking
- bilateral vestibular schwannoma
- highly motivated
- reasonable expectations
- psychologically stable
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
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
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
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
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
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)
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
