The Richard Ramsden Centre for Hearing Implants

Manchester

Annual Report 2017-2018

COCHLEAR IMPLANT TEAM

Andrew Causon – Audiologist

Andy Cooper – Assistant Audiologist

Angela Fuller – Assistant Audiologist

Anne Stockbridge – Administrator

Christine Melling – Adolescent Coordinator and Speech & Language Therapist

Craig Went – Audiologist

Deanne Jayewardene-Aston – Audiologist

Deniece Walker – Administrator

Deborah Mawman – Adult Coordinator and Audiologist

Elizabeth Whittle – Audiologist

Emma Gray – Speech & Language Therapist

Emma Stapleton – Surgeon

Helen Ley – Speech & Language Therapist

Iain Bruce – Surgeon

Jayne Jones – Speech & Language Therapist

Karen Smith – Hearing Therapist

Kerri Millward – Audiologist

Lise Henderson – Paediatric Coordinator and Speech & Language Therapist

Martin O’Driscoll – Head of Department and Audiologist

Morag Lockley – Audiologist

Rebecca Bentley – Teacher of the Deaf / Auditory Verbal Therapist

Sarah Hornby – Audiologist

Simon Freeman – Surgeon

Simon Lloyd – Surgeon

Tamasin Brown – Audiologist

Unai Martinez de Estibariz – Audiologist

Vicki Carek – Clinical Psychologist

ADULT COCHLEAR IMPLANT PROGRAMME

Introduction

Cochlear implantation has been established in the UK for over 3 decades and

there are currently just over 17000 patients in the UK using cochlear implants

(see Figure 1). In the UK, cochlear implants are funded by NHS England (Ref:

D09/S/A) if patients meet the NICE guidance (Ref: TA166. This guidance is

currently under review.

Figure 1: Total number of maintained patients in the UK (from BCIG’s annual

data collection 2017-18)

The auditory implant programme in Manchester was established in 1988 by ENT

Consultant Richard Ramsden, using funding to provide cochlear implants obtained

from the HEAR (Help Ear & Allied Research) Charity. In the mid 1990’s government

resources became available to fund cochlear implants for patients with severe-

profound sensori-neural hearing loss. By the end of March 2018, 1274 adults have

received a cochlear or an auditory brainstem implant in Manchester manufactured by

Advanced Bionics, Cochlear and MED-EL.

10708

749

1914

3727

ADULTS - unilateral

ADULTS - bilateral

CHILDREN - unilateral

CHILDREN - bilateral

Criteria for referral to the adult programme for cochlear implants

There is no maximum age for referral and patients with additional needs are not

excluded (Ref: NICE TA166):

✦ Bilateral, severe to profound sensori-neural hearing loss (≥ 90 dB HL

at 2 and 4 kHz).

✦ Limited or no benefit from hearing aids (a score of 50% or less on

BKB sentence testing at a sound intensity of 70 dB SPL in the ear to

be implanted).

✦ Simultaneous bilateral cochlear implantation is recommended as an

option for adults who are blind or who have other disabilities that

increase their reliance on auditory stimuli as a primary sensory

mechanism for spatial awareness.

✦ Cochlear implantation is considered for adults only after an

assessment by a multidisciplinary team. As part of the assessment

adults should also have had a valid trial of an acoustic hearing aid for

at least 3 months (unless contraindicated or inappropriate).

Clinical activity between April 2017 and March 2018

✦ Procedures

During the 2017-18 financial year, a total of 115 cochlear implant procedures

were performed in adults. Figure 2 shows a breakdown of the types of surgeries

performed.

Figure 2: Surgical procedures

✦ Explantations

Three explantations were carried out, all due to medical problems (D) based on

the International Classification of Reliability for Implanted Cochlear Implant

Receiver Stimulators (see figure 3). Two of the explanted patients were

successfully re-implanted. One patient continues to suffer from recurrent ear

infections in the implanted ear which may be related to a pre-existing medical

condition and their management is on-going.

Figure 3: International Classification of Reliability for Implanted Cochlear Implant

Receiver Stimulators (Battmer et al., 2010)

103

2 3

5 2

Cochlear Implantation(unilateral)

Cochlear Implantation(sequential)

Explantation

Re-implantation

Repositioning

✦ Devices

Excluding explantation and repositioning procedures, a total of 110 devices were

fitted in this financial year. Detailed charts on the types of internal devices,

manufacturers and type of speech processor are shown in figures 4 to 6.

Figure 4: Implant electrode arrays by type

Figure 5: Implants by manufacturer

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3 1

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28

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Medel

Cochlear

Advanced Bionics

Figure 6: Speech processors by configuration

✦ Demographics

The average and median age of the patients implanted was 56 years (range = 19

- 94 years). Figure 7 shows the age distribution of the implanted adult population

during the 2017-2018 financial year period.

Figure 7: Age of patient at implant

✦ Post-implant support

Patients typically attend 5 appointments with the adult team within their first six

weeks of implant use. During these appointments the speech processor is

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Behind the ear

Off the ear

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programmed and patients receive rehabilitation through an individualised

auditory and communication skills training programme with a therapist. Where

appropriate, the training programme includes tactics for using the telephone,

music therapy and advice about using assistive listening devices. Patients are

then followed up at three, nine and twenty-one months after their initial

activation. Additional rehabilitation sessions are offered to patients as required.

Following this, a patient led appointment is sent on an annual basis. Every 6

years the patient will be offered a speech processor upgrade.

✦ Outcomes

Speech perception and lip-reading function is measured using standardized

recorded test materials for each patient at the pre-implant stage. Following

implantation, the tests are repeated at one week, three months, nine months and

twenty-one months, and then annually as required. Patients who use English as

a second language, or who cannot communicate in English are evaluated in their

own language using language interpreters to translate the test materials to the

appropriate language.

Figure 8 shows the average scores obtained using the Bamford-Kowal-Bench

(BKB) sentence test in quiet at pre- and post-operative stages in this financial

period.

Figure 8: Speech perception scores

10.3

28.8

62.4

77.2

51.8

75.9

85.2

0

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100

Pre-op 1 week 3 months 9 months

Bilateral Hearing Aids Cochlear Implant only Bimodal (Cochlear Implant + Hearing Aid)

Sound-field aided thresholds are also measured post operatively. Figure 9 shows

the average aided thresholds at the 1 week, 3 month and 9 month stage, as well

as their average pre-op unaided thresholds. Thresholds ≤ 40 dB HL at

frequencies between 250 and 8000 Hz allow good access to normal

conversational speech levels and everyday sounds and are considered optimal

for cochlear implant users.

Figure 9: Threshold levels at pre op and post stages

Service evaluation

A satisfaction questionnaire is sent to all newly implanted users at their 9 month post

implant stage to gauge their views on their cochlear implant progress and our service.

All responses are anonymous. Below are a few responses collected during the last

financial year:

91% of respondents report that their cochlear implant exceeded their

expectations or that it was too soon to comment.

100% of respondents report using their cochlear implant every day (all day

long or part of the day)

91% of respondents report obtaining great benefit from their cochlear implant

100% of respondents feel it was worthwhile having a cochlear implant

0

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250 500 1000 2000 4000 8000

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Pre Op 1 Week 3 Months 9 Months

100% of respondents would recommend a cochlear implant to a friend or

relative if they had a similar hearing problem

100% of respondent were satisfied with the treatment/support that they

received from the staff on the cochlear implant programme

100% of respondents rated the treatment/support that the staff at the cochlear

implant programme provided as very good

Below are statements from respondents with regards to why they felt this treatment

was worthwhile:

“For so much of my life I have felt foolish and odd because I could not hear so I would

withdraw into myself.

“Their support has brought me out into the sunshine”

“It has given me my life back. I can go out now and be part of a conversation where

before you are isolated”

“I am no longer excluded from conversation”

“It has given me confidence to go places alone. it has completely changed my and

that of my family”

“I can now hold a conversation clearly and not afraid to be in company”

Among the disadvantages noted by cochlear implants users, the following were

reported: one patient reported short battery life, another patient noted louder but non-

troublesome tinnitus and one other patient reported discomfort when wearing their

device.

PAEDIATRIC COCHLEAR IMPLANT PROGRAMME

Introduction

The Paediatric Programme at the RRCHI was established in October 1991 and to March

2016, 864 children (ages 0-11) have received cochlear implants on the programme.

Members of the team have experience in working with children of widely differing age,

history of hearing loss, cultural and educational background. We also work with children

with a wide range of additional disabilities.

All patients referred to the Paediatric Programme undergo a full audiological assessment

involving a series of appointments with the team. All children with congenital hearing losses

would normally be expected to be wearing appropriately-fitted high powered hearing aids

throughout the assessment process. Diagnostic habilitation may be used to assess the

current benefit a child receives from hearing aids as well as to identify additional factors

which may affect learning with a cochlear implant system. In addition, as part of the

assessment programme, the child will undergo an MRI (Magnetic Resonance Imaging)

scan in order to confirm the presence of a cochlear nerve, and determine the suitability of

the inner ear to receive an implant. Some children may also require a CT scan but this is

not routinely undertaken. For children with a sudden, acquired hearing loss (particularly

following meningitis, where there risk of cochlear ossification leading to surgical

complications) a fast track programme is in place to enable surgical priority.

Criteria for referral to the paediatric programme for cochlear implants

Criteria are selected according to evidence-based practice and experience. They are set to

ensure that those children who receive a cochlear implant are those most likely to obtain

benefit from the device. The younger a child is when he/she receives a cochlear implant,

the more successful the outcome is likely to be. A child who receives a cochlear implant at

the age of 4 years will be less likely to successfully acquire fluent spoken language than a

child who receives a cochlear implant at the age of 18 months.

We would therefore recommend that any child, however young, who is suspected of having

a significant hearing impairment should be referred to the cochlear implant team as soon as

possible. This will allow the cochlear implant team to begin carrying out assessments, and

informing parents about cochlear implants, in parallel with the ongoing audiological

assessments and hearing aid fitting being carried out by the child’s local services.

In cases where a child receives a unilateral implant, the Paediatric Programme encourages

children to continue wearing a contralateral hearing aid if they have residual hearing in the

non-implanted ear.

None of the criteria outlined below exclude children with additional physical disabilities or

learning difficulties. Referrals for assessment are accepted for:

• Referral from first ABR where levels indicate cochlear implant may be appropriate.

• Children who were born with a profound hearing loss, receive no significant benefit

from hearing aid and are under the age of 4 years at the time of referral

• Children under the age of 10 years who were born with normal hearing and have

acquired a profound hearing loss, e.g. following meningitis. A child with a suspected

hearing loss following meningitis should, of course, be referred for assessment

immediately so that cochlear implant surgery can be fast-tracked in the event of any

ossification of the cochlea.

• Children under the age of 10 years who have had some benefit from hearing aids in

the past, but whose hearing has deteriorated to the point where powerful hearing aids

are no longer helpful and / or have shown benefit for language learning through

consistent use of powerful hearing aids but who might receive significantly more

auditory information from a cochlear implant (NB. These patients should show

evidence that they have learnt spoken language through listening, thus demonstrating

the integrity of the auditory pathway)

• Children diagnosed with ANSD and have consistent behavioural hearing thresholds

bilaterally in the severe-profound SNHL range (≥90dBHL at 2 and 4 kHz) should

always be referred to the cochlear implant programme. There is no minimum age of

referral but it is still important to refer these children early. Children with ANSD and

with additional needs should not be excluded. Children with ANSD can also be

referred to the implant programme if they are making poor progress with their hearing

aids despite having unaided thresholds outside implant criteria. We classify poor

progress as:

Unable to consistently discriminate the ling sounds

Unable to imitate pattern perception (duration and number of syllables in a

word)

Only able to understand simple instructions with visual cues e.g. pointing

Not making the appropriate progress with spoken language development with

their hearing aids

Have not achieved behavioral hearing levels by 14 months of age.

• Children with one ear in the profound range and the other ear in the moderate /

severe range. We accept referrals of all children who meet this criteria, but those over

the age of 4 must be developing spoken language.

• Children with auditory nerves dysplasia. Children with suspected thin or absent

nerves should also be referred to the paediatric team. We can assess these children

using electronic auditory brainstem response to assess the ability of the auditory

nerve to carry auditory responses. If good traces are obtained then these children may

be still eligible for a cochlear implant. Those with absent nerves or have poor eABR

traces can then be referred for an Auditory Brainstem Implant if the parents and

professionals feel it is appropriate.

Please note:

• Early referral is encouraged (from ABR if possible / appropriate) and is extremely

important to help children who need a cochlear implant to get one as quickly as

possible.

• If you are unsure about a referral or unable to obtain behavioural levels please speak

to us beforehand or send a referral. We are happy to see people for second opinions.

• That children aged 10 years and over should be referred to the Adolescent

Programme.

Clinical activity between April 2017 and March 2018

✦ Surgeries

A total of 55 children (a total of 89 cochlear implants) have been implanted during this

financial year. A detailed info-graphic on the types of implants, processors and

configuration of implantation is shown below.

Figure 10: Breakdown of implanted ears for children implanted in 2017-2018

Bilateral, 34

Unilateral, 14

Sequential, 1 Reimplant, 6

Figure 11: Breakdown of internal implants for children implanted in 2017-2018

Figure 12: External devices for children newly implanted in 2017-2018 (excluding

reimplants)

✦ Demographics

The average age of paediatric cochlear implant patients was 3 years (range = 9

months - 8 years 10 months). Figures 13 and 14 show the age distribution and

Advanced Bionics, HR 90K

Advantage Hi Focus

1J, 1

Advanced Bionics, Hi Focus Ultra

MS, 2

Medel, Synchrony Flex 28, 5 Cochlear,

CI522, 47

Advanced Bionics,

Neptune, 1

Advanced Bionics, Naida, 1

Medel, Opus 2, 1

Cochlear, CP910, 46

hearing loss aetiology of the implanted children population at the RRCHI during the

2017-2018 financial year period.

Figure 13: Age distribution of children receiving cochlear implants for the first time (reimplant and sequential patients not included)

Figure 14: Aetiology of children receiving unilateral or bilateral cochlear implants (reimplant and sequential patients not included)

BVVL = Brown Vialetto Van Laere Syndrome, ANSD = Auditory Neuropathy Spectrum

Disorder, CMV = Cytomegalovirus, WVA = widen vestibular aqueducts

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Aetiologies

✦ Outcomes – Implant Use

We carry out the Brief Assessment of Parental Perception (BAPP) after 2 years of

implant use. This is a questionnaire gives the parents perception of their child’s

implant use and willingness to wear implant and whether they would recommend a

cochlear implant to other parents. It also asks for comparisons in their child’s in

behaviour, contentment, communication learning and getting on with friends pre-

implant compared to post. After 2 years of use, all patients wore their processor(s) at

least some of the day, with the majority wearing it full time. The willingness for

paediatric patients to wear their processor(s) at 2 years of use can be seen in Figure

15. The majority are very keen to wear. One hundred percent of the parents who

completed the questionnaire would recommend cochlear implantation to another

family in a similar situation.

Figure 15: Paediatric patients’ willingness to wear their after 2 years of use

✦ Outcomes – Aided Levels

The paediatric patients are seen regularly in their first year of implant use to establish

good listening levels. We categorize good listening levels to be between 20 and 40 dB

HL using sound field testing (warble tone). With some children who have

Percentage of paediatric patients willingness to wear their processor(s) after their second year of use

Very keen

Keen

Neutral

Reluctant

Very reluctant

developmental delay it is often not possible to test aided levels. We therefore rely on

objective and behavioral testing to establish that the processor is set optimally for the

patient. Figure 16a shows the average aided levels achieved 1 year post implant.

These levels are also checked at two years of use and remain stable (Figure 16b)

Figure 16: a) Average aided levels for the first year of implant use

Figure 16: b) Average aided levels for the second year of implant use

Within the first year of implant use, 100 % of paediatric patient that were able to do

behavioural testing achieved average aided thresholds of 40 dB HL or better.

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Average aided levels of paediatric patients after the second year of use

✦ Post-Implant Support

Children are generally offered regular habilitation sessions during their first three

years of cochlear implant use. These sessions are designed to ensure that the child

obtains maximum benefit from the cochlear implant. Therapists work with parents or

caregivers to help the child to develop spoken language through listening. Our

habilitation programme is based on Auditory Verbal Therapy. Children also have

regular appointments for reprogramming of the speech processor.

Over time primary responsibility for a child’s habilitation programme is handed back to

the local support services. However, the implant team is always available to provide

advice, support and training to local professionals if required/requested. Children

continue to be seen annually by the cochlear implant team for equipment checks,

reprogramming and speech perception assessments.

✦Outcomes – PLS

The Preschool Language Scales is standardized on normally hearing children aged

from infancy to 6 years 11 months. The purpose of this assessment is to assess

children’s receptive and expressive language capabilities. Responses range from

parental report to picture selection and completion of open-ended sentences. The

high level of contact between the team and children in their first two years of cochlear

implant use enables habilitationists to pinpoint a child’s current level of development.

For longer term implant users, reports from parents and local support professionals,

together with the child’s performance on standardized assessments administered at

the annual review, are used to determine their level of attainment on the scale. Figure

17 shows the outcomes of the PLS preimplant, and 1 and 2 years of implant use. The

data show that the children on average of their age equivalent scores are catching up

to their chronological age.

Figure 17: Average difference between chronological age and language age as a

percentage for paediatric patients at preimplant and 1 and 2 years post implant use

-70

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Difference between chronological age and language as a percentage (if at 0 % no difference between chronological

age and language score on the PLS) 2017-18

AUDITORY BRAINSTEM IMPLANT PROGRAMME

Introduction

The implant centre in Manchester has the largest population of auditory

brainstem implant (ABI) users in the UK. The majority of these patients have

Neurofibromatosis Type 2.

The auditory brainstem implant (ABI) depicted in figure 18 evolved from cochlear

implant technology to address the problems of rehabilitating patients with total

deafness with a damaged or absent cochlear nerve, and are therefore unsuitable

for cochlear implantation. The great majority of these patients suffer from the

genetic disorder called neurofibromatosis type 2 (NF2). NF2 affects one in

33,000 people and is characterised by the development of bilateral vestibular

schwannomas (tumours on the hearing and balance nerves). More recently other

indications for ABI have been approved including cochlear nerve aplasia or

severe dysplasia in infants, extreme degrees of inner ear dysplasia even in the

presence of normal looking auditory nerves, severe cochlear obliteration from

otosclerosis or meningitis, and head injury with cochlear nerve avulsion. These

conditions prevent effective cochlear implantation.

Figure 18: The auditory brainstem implant and external speech processor

The ABI stimulates the cochlear nucleus complex on the brainstem directly and

bypasses any damaged or absent cochlear nerve. The ABI electrode array is

placed on the surface of the cochlear nucleus complex on the floor of the

foramen of Luschka in the lateral recess of the fourth ventricle of the brainstem

(see figure 19).

Figure 19: Placement position of the auditory brainstem implant

The external speech processor for an ABI is activated about 6 weeks post-

surgery and patients undertake a similar programme of tuning and rehabilitation

to cochlear implant patients. The ABI provides limited speech understanding for

patients although it can help patients to understand speech better with lipreading

(see figure 20). It also helps patients to hear and identify everyday sounds.

Figure 20: Comparison of CUNY scores (N = 49) using the ABI only, lipreading

(LR) only and the ABI with lip-reading (Ramsden et al., 2016)

Manchester is one of only two centres in the UK commissioned to provide ABI’s.

For adults, the ABI surgery takes place at Salford Royal NHS Foundation Trust

and for children the surgery takes place and the Royal Manchester Children’s

Hospital. The ABI programming and rehabilitation takes place within the Richard

Ramsden Centre for Hearing Implants.

To date, the team has performed 82 ABI surgeries in 73 adults and 9 children.

MEDIA AND PUBLIC RELATIONS

In November 2016, Channel 4 broadcasted an observational documentary LIVE

from the Richard Ramsden Hearing Implant Centre titled “Breaking the Silence”.

The programme allowed viewers to share the moment eight patients heard for

the first time when their cochlear implant was switched on. Staff and patients

from the Manchester implant centre as well as other centers from around the UK

(see picture 21), were involved in the ground breaking documentary.

Picture 21: Some of the clinicians involved in the live broadcast programme

This documentary can be viewed online in the following link:

http://www.channel4.com/programmes/breaking-the-silence-live/on-

demand/63119-002

Following the live broadcast, our Head of Department, Martin O’Driscoll,

appeared on the BBC Breakfast TV programme to talk about the benefits of

cochlear implantation.

Picture 22: Martin O’Driscoll at the BBC One Breakfast show

REFERENCES

Management of Cochlear Nerve Hypoplasia and Aplasia Freeman SR, Sennaroglu L. Adv Otorhinolaryngol. 2018;81:81-92. doi: 10.1159/000485542. Epub 2018 Apr 6.

Hearing preservation cochlear implantation in children: The HEARRING Group consensus and practice guide Rajan G, Tavora-Vieira D, Baumgartner WD, Godey B, Müller J, O'Driscoll M, Skarzynski H, Skarzynski P, Usami SI, Adunka O, Agrawal S, Bruce I, De Bodt M, Caversaccio M, Pilsbury H, Gavilán J, Hagen R, Hagr A, Kameswaran M, Karltorp E, Kompis M, Kuzovkov V, Lassaletta L, Yongxin L, Lorens A, Manoj M, Martin J, Mertens G, Mlynski R, Parnes L, Pulibalathingal S, Radeloff A, Raine CH, Rajeswaran R, Schmutzhard J, Sprinzl G, Staecker H, Stephan K, Sugarova S, Zernotti M, Zorowka P, Van de Heyning P. Cochlear Implants Int. 2018 Jan;19(1):1-13. doi: 10.1080/14670100.2017.1379933. Epub 2017 Oct 26.

Review of outcomes and measurement instruments in cochlear implantation studies Schaefer S, Henderson L, Graham J, Broomfield S, Cullington H, Schramm D, Waltzman S, Bruce I. Cochlear Implants Int. 2017 Sep;18(5):237-239. doi: 10.1080/14670100.2017.1353761. Epub 2017 Jul 25. No abstract available.

Hearing optimisation in neurofibromatosis type 2: A systematic review Lloyd SKW, King AT, Rutherford SA, Hammerbeck-Ward CL, Freeman SRM, Mawman DJ, O'Driscoll M, Evans DG. Clin Otolaryngol. 2017 Dec;42(6):1329-1337. doi: 10.1111/coa.12882. Epub 2017 Apr 26.

United Kingdom national paediatric bilateral project: Results of professional rating scales and parent questionnaires Cullington HE, Bele D, Brinton JC, Cooper S, Daft M, Harding J, Hatton N, Humphries J, Lutman ME, Maddocks J, Maggs J, Millward K, O'Donoghue G, Patel S, Rajput K, Salmon V, Sear T, Speers A, Wheeler A, Wilson K. Cochlear Implants Int. 2017 Jan;18(1):23-35. doi: 10.1080/14670100.2016.1265189. Epub 2017 Jan 18.

Consensus statement: Long-term results of ABI in children with complex inner ear malformations and decision making between CI and ABI Sennaroğlu L, Colletti V, Lenarz T, Manrique M, Laszig R, Rask-Andersen H, Göksu N, Offeciers E, Saeed S, Behr R, Bayazıt Y, Casselman J, Freeman S, Kileny P, Lee DJ, Shannon RV, Kameswaran M, Hagr A, Zarowski A, Schwartz MS, Bilginer B, Kishore A, Sennaroğlu G, Yücel E, Saraç S, Ataş A, Colletti L, O'Driscoll M, Moon IS, Gärtner L, Huarte A, Nyberg G, Mocan BÖ, Atay G, Bajin MD, Çınar BÇ, Batuk MÖ, Yaralı M, Aydınlı FE, Aslan F, Kirazlı MC, Özkan HB, Hans JM, Kosaner J, Polak M. Cochlear Implants Int. 2016 Jul;17(4):163-171. Epub 2016 Jul 21. No abstract available.

Preliminary assessment of the feasibility of using AB words to assess candidacy in adults Vickers DA, Riley A, Ricaud R, Verschuur C, Cooper S, Nunn T, Webb K, Muff J, Harris F, Chung M, Humphries J, Langshaw A, Poynter-Smith E, Totten C, Tapper L, Ridgwell J, Mawman D, de Estibariz UM, O'Driscoll M, George N, Pinto F, Hall A, Llewellyn C, Miah R, Al-Malky G, Kitterick PT. Cochlear Implants Int. 2016 Apr;17 Suppl 1:17-21. doi: 10.1080/14670100.2016.1161143.

Self-Reported Listening-Related Effort and Fatigue in Hearing-Impaired Adults. Alhanbali S1, Dawes P, Lloyd S, Munro KJ. Ear Hear. 2017 Jan/Feb;38(1):e39-e48

Auditory Brainstem Implantation in Neurofibromatosis Type 2: Experience From the Manchester Programme Ramsden RT, Freeman SR, Lloyd SK, King AT, Shi X, Ward CL, Huson SM, Mawman DJ, O'Driscoll MP, Evans DG, Rutherford SA; Manchester Neurofibromatosis Type 2 Service. Otol Neurotol. 2016 Oct;37(9):1267-74. doi: 10.1097/MAO.0000000000001166.

TA166 - Cochlear implants for children and adults with severe to profound deafness National Institute of Clinical Excellence. Published date: 28 January 2009 (https://www.nice.org.uk/guidance/ta166)

D09/S/A - NHS standard contract for cochlear implants NHS Commissioning Board, 2013 (https://www.england.nhs.uk/commissioning/wp-content/uploads/sites/12/2014/04/d09-ear-surg-coch-0414.pdf)

Figure XXX: BKB sentence scores (auditory alone)