Week 13 ABI

Question 1

what is the most successful sensory prosthetic device developed

Answer 1

• cochlear implants

- –but they are not for everybody

Question 2

what pts do not benefit from CIs

Answer 2

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

Question 3

the very first ABI

Answer 3

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

Question 4

what is NFII

Answer 4

• 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

Question 5

first multichannel ABI

Answer 5

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

Question 6

how does an ABI function

Answer 6

• 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

Question 7

current approved ABI devices in the US

Answer 7

• 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

Question 8

other ABI devices not yet approved in the US

Answer 8

• Med-el Concerto ABI

* Oticon diagnostic SP ABI

Question 9

ABI candidacy criteria in the US

Answer 9

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

Question 10

ABI candidacy criteria outside the US

Answer 10

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

Question 11

ABI surgery basics

Answer 11

• 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

Question 12

what is the placement goal of an ABI surgery

Answer 12

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

Question 13

retrosigmoid approach to ABI surgery

Answer 13

• 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

Question 14

translabyrinthine approach to ABI surgery

Answer 14

• 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

Question 15

3 major complications of ABI implantation

Answer 15

• 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)

Question 16

activation of ABI

Answer 16

• 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

Question 17

ABI outcomes

Answer 17

• 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

Question 18

who is not an option for benefit from vestibular implant

Answer 18

• 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

Question 19

who might benefit from a vestibular implant

Answer 19

• 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

Question 20

sensor-based design of vestibular implant

Answer 20

• 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

Question 21

pacemaker-based design of vestibular implant

Answer 21

• 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

Question 22

first vestibular implant prototype

Answer 22

• 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

Question 23

nucleus freedom vestibular implant system

Answer 23

• 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

Question 24

multichannel vestibular implant (MVP 1,2)

Answer 24

• 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

Question 25

multichannel vestibular prosthesis (MVP1, 2)

Answer 25

* 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