2020-09-29
Intervention strategies for air‐ and bone‐ conduction unilateral hearing loss (UHL)
Susan A. Small, PhD Associate Professor Hamber Professor of Clinical Audiology University of British Columbia
Virtual Speech & Hearing BC Conference 2020 October 23, 2020, 10:30 am ‐ 12:00 pm
Disclosure statement . NSERC Discovery Grant . BC Early Hearing Program (consultant): receive funds & equipment that contribute to my research program . Hamber Chair position: small contribution to research program . Interacoustics: equipment on loan
Other funding . UBC Faculty of Medicine: general funds for research . Eric W. Hamber Professorship: partial salary award
TOPIC AREAS TO BE ADDRESSED Prevalence of UHL Loss of binaural hearing benefits with UHL‐‐ effects on spatial hearing + other consequences Review of current data re: intervention for UHL across the lifespan‐‐ infants to adults Bone‐conduction hearing loss: Unilateral & binaural
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BC EHP Definitions
Unilateral hearing loss (UHL)
Normal hearing in one ear (considered to be the majority of thresholds ≤ 20 dB HL) Majority of air‐conduction (AC) thresholds >20 dB HL in the ear with permanent hearing loss
Historically, audiologists most concerned with effects of severe‐to‐profound hearing loss on speech & language development
Rubella outbreak in US Severe/profound clinical in 1964/5: 12,000 babies focus for years after born deaf UHL (& minimal bilateral hearing loss) might have Studies in negative effects on academic early 1980’s progress & psychosocial skills of school‐aged children
** Renewed research focus in last 3-5 years
Unilateral hearing loss
Focus of recent international conferences ‐ BCEHP Workshop 2017, Oct 17, 2017, Vancouver: R. McCreery, J. Lieu & S.A. Small ‐ Phonak Unilateral Hearing Loss in Children Conference 2017, Oct 22‐24, 2017, Philadelphia
‐‐ lack of clarity re: best practice for UHL ‐‐ recent changes for infant UHL followed (e.g., BC & ON)
Today: overview of past & more recent research available to guide clinicians... some data to guide us but more needed, particularly for infants & young children!
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mild conductive NH mixed sensory/neural profound
Prevalence of UHL • with age • Newborns: ~ 0.6‐0.7 in 1000 (2013‐14 est. from CDC) ‐ ~1/3 of children with congenital hearing loss (progresses to bilateral in 7.5‐11.5%) (Paul et al., 2017; Haffey et al., 2013) • School age: 2.5‐3.0 % > 25 dB HL ‐ 19.5% with hearing thresholds >15 dB HL (Shargorodsky et al., 2010)
mild conductive NH mixed sensory/neural profound Prevalence of UHL cont’d • May also help to follow infants at risk for progressive‐late‐onset ‐ >50% Enlarged Vestibular Aqueduct (EVA)/Mondini dysplasia ‐ + acquired CMV, genetic causes, NICU stay, in utero infections, craniofacial anomalies & postnatal infections/syndromes (reviewed in Bagatto et al., 2019)
Audiologist should recommend complete otological evaluation with imaging
Main concern for UHL: loss of hearing benefits associated with binaural hearing – effects on spatial hearing + other effects ‐ localization ‐ speech in noise ‐ early auditory behaviours/pre‐verbal vocalizations (Kishon‐Robin et al., 2015)
‐ speech/language development (Ead et al., 2013; Lieu, 2013) ‐ academic success (Bess & Tharpe, 1986; Lieu, 2004, 2013) ‐ balance (Wolter et al., 2016) Still do not have clinically feasible approach to assess spatial hearing ‐ some recommend survey/questionnaires (ABEL, SSQ) ‐ others: anechoic chamber/sound booth with speaker arrays (much harder to do clinically) (reviewed in Bagatto et al., 2019)
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Still early days re: evidence of effectiveness of intervention strategies available to ameliorate deficits for UHL ‐‐ what are the challenges? ‐‐ what do we know/not know?
UHL & device use One challenge re: best practices for device recommendations for UHL in infants/children – no consensus but some suggestions…. Limited high‐level evidence of benefit (or harm) for different ages, types of losses & devices e.g., recent systematic review identified only 12‐13 studies with functional/objective auditory outcomes; 7 with bone‐ anchored hearing systems (BAHS) (Appachi et al. ,2017; Anne et al., 2019) BUT….
# studies investigating UHL starting to increase: ‐ Clinical outcomes: hearing aids (HA), CIs, BAHS, CROS & FM ‐ Cortical plasticity and binaural hearing in infants/children/adults with normal hearing (NH) & UHL‐‐ although mostly post‐lingual populations– more on this… ‐ Measures to assess binaural benefit with devices
Some clinical questions yet to be answered fully… but now more clinical data available! Will devices improve long‐term effects of UHL on speech/language development/academic success/psychosocial function, or only for some children? How should we manage conductive vs sensory/neural UHLs? Air‐ conduction HAs versus BAHS (softband/implanted)? CI? CROS? FM? How should we plan intervention for mild‐moderate vs severe‐ profound UHL? Should intervention strategies for infants, children & adults differ? Are there any detrimental/limited benefits depending on type of UHL, type of device, or age of child?
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Reaching consensus on best practices for intervention for UHL in infants and young children difficult for several reasons:
‐ For many years, conflicting findings & low‐level evidence regarding long‐term effects on academic success & psychosocial function
‐ Limited data available supporting intervention with hearing aids, CIs, FM systems &/or communication strategies results in better speech & language outcomes
More data in last 4‐5 years: more aggressive hearing‐aid fitting approaches & implantation of CIs
(for review: McKay et al. 2008; Lieu 2015)
Other questions re: UHL Do devices actually restore binaural hearing? How do we explain variability in binaural benefit with devices?
Concepts that relate to binaural hearing: • head shadow, binaural summation, & binaural squelch • with UHL, typically lose benefits related to these phenomena & additionally experience negative effects relating to head shadow, if speech directed toward ear with UHL (shadows speech signal to NH ear)
Infants & preschoolers Mixed early findings re: effects of UHL on language development ‐ some showed effects, some did not!
Ex. 1 (Kiese‐Himmel (2002) Retrospective study over 4 yrs; 1 mos to 10 yrs (NH vs UHL) ‐UHL: no delay in production of first word & no difference on standardized linguistic tasks vs NH infants ‐ BUT infants with UHL produced first 2‐word combinations 5 mos later than NH infant (but not outside of normal range)
Ex.2 (Sedey et al. [results reported in Lieu (2004)] ‐ 4/15 of 12‐mos‐old infants with UHL showed language delays in the absence of any known disabilities
Renewed research focus on UHL & infants auditory development in last 4‐5 years
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Infants & preschoolers More infant UHL data to support intervention
Ex. 1: (Lieu et al., 2010) ‐UHL: delay in 1st 2‐word phrase by parent recall vs NH
Ex. 2: (Kishon‐Rabin et al., 2015; 34 UHL, 331 NH; ~9 month‐old infants) ‐ auditory behavior (IT‐MAIS) delayed in 21% UHL vs 4% NH ‐ preverbal vocalization (PRISE) delayed in 41% UHL vs 4% NH
Ex. 3: (Fitzpatrick et al., 2015; 31 UHL; 45 NH (12, 24, 36, & 48 mos) ‐ Assessment tools: PEACH/ELF/CHILD/MacArthur‐ Bates/MLU/CDI ‐ CHILD scores worse at age 36 & 48 mos
Important question: if device used for UHL, does bilateral auditory stimulation automatically result in restored spatial hearing ??? One of the early studies (only 2017!) looked at bilateral hearing loss and bilateral CIs‐‐ interesting findings: cortical representation of interaural time differences (ITDs) (Easwar et al., 2017) • NH vs children with simultaneous bilateral CI implantation (<3.5 y; 2 y auditory experience) (Young children‐ not infants) NH CIs
L leading --R lateralization ITDs: ITDs: no difference in preference R leading-- more bilateral activation for R & L leading - Clear behavioural responses to ITD cues - Poor behavioural responses to ITD cues - Lower than NH in non-auditory areas ‐‐ Bilateral simultaneous electrical stimulation essential to protect bilateral auditory pathways from unilateral‐driven re‐organization BUT not sufficient for normal development of ITD coding
Possible reasons for bilateral CI findings? Effect of early auditory deprivation? Type of hearing experience? Reliable ITDs unavailable from CIs functioning independently? CIs change ITDs of signal fine structure? Greater neural synchrony from electrical pulses affects timing cues? CI input affects brainstem coding? Less efficient compensatory strategies being used instead of ITD cues?
More in later section about CIs and UHL
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Effects of UHL across the lifespan: Infants Toddlers School‐age children Adults
School‐age children number of studies investigated effects of UHL on school‐age children (6‐18 years)
‐ showed poorer localization skills compared to NH children: ↓ performance with ↑ severity loss (Bess et al., 1996) ‐ consistently showed poorer performance in school ‐ 18‐35% repeated at least one grade in school (3.5% failure rate in general population) ‐ 12‐60% required a resource teacher (Bess & Tharpe, 1986; Oyler et al.,1988; Bovo et al., 1988; Jensen et al.,1989; Lieu 2004, 2010, 2012)
School‐age children Early research showed varied results for speech/language/cognition
IQ findings ‐ slight decrement in verbal IQ relative to performance IQ (Davis et al., 1981) ‐ no difference NH vs UHL children for 2 different IQ tests BUT children with more severe UHL had significantly lower overall IQ scores vs children with less severe UHLs (Culbertson & Gilbert, 1986)
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School‐age children Earlier & more recent data showed specific auditory deficits with UHL reported (but variable & not all cases!) ‐ poorer scores on word recognition/spelling subtests vs NH peers (Culbertson & Gilbert, 1986) ‐ poorer speech recognition scores vs NH children (quiet & noise; stimuli directed to better or poorer ear; different azimuths) (Newton et al., 1983; Bess & Tharpe, 1986; Bovo et al., 1988; Ruscetta et al., 2005) ‐ lower scores on morphology, syntax, vocabulary BUT similar performance for short‐term & working memory (Sangen et al., 2017) ‐ poorer auditory/visual performance for UHL vs NH but not related to visual‐fixation differences as hypothesized (Lewis et al., 2018) ** risks greater for children with more severe UHL (Culbertson & Gilbert 1986; Lieu et al. 2013)
School‐age children UHL vs NH results in greater speech recognition difficulties in noise ‐ greatest effect when speech directed toward ear with hearing loss (Ruscetta et al. 2005) ‐ UHL hearing also worse when speech and noise spatially separated, noise is complex, or SNR is poor (Reeder et al., 2015; Corbin et al., 2017; Bess et al., 1986)
Note: poorer auditory/visual performance for UHL vs NH but not related to visual‐fixation differences as hypothesized (Lewis et al., 2018)
Also, a few studies showed no speech and language deficits for UHL (Hallmo et al., 1986; Kiese‐Himmel, 2002)
School‐age children
Studies as early as 1967 reported psychosocial problems in children & adolescents with UHL ‐ adolescents with UHL experienced feelings of confusion, annoyance/embarrassment/helplessness (Giolas & Wark, 1967) ‐ 20‐42% with UHL demonstrate behavioural problems (Stein, 1983; Bess & Tharpe, 1986; Culbertson & Gilbert 1986; Brookhouser et al. 1991; Lieu et al. 2010) ‐ 37% of these children scored below normal range for interpersonal & social adjustment (Stein, 1983) ‐ children with UHL exhibited problems with attention despite achieving within normal limits academically (Dancer & colleagues, 1995)
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School‐age children Relatively recently… lower quality of life reported by children & adolescents with UHL vs NH (more similar to children with bilateral hearing loss than NH!)
Hearing Environments & Reflection on Quality of Life survey (HEAR‐QL) • Self‐reported UHL
(Rachakonda et al., 2014)
School‐age children
Very brief summary • currently, sufficient data support that some children with UHL will have academic and psychosocial problems • one challenge is predicting which children with UHL will experience these problems … led to increase in research
Adults Only a few studies attempted to investigate long‐term effects of UHL in adults– not so different from NH ‐ adults with UHL from childhood showed similar academic success as NH adults & no differences in type of employment (Colletti et al., 1988) ‐ UHL prevalence in 1st year university students at a prestigious Japanese institution (.16%) similar to prevalence of UHL in school‐age children (.15%) ‐ UHL did not appear to be linked to long‐term educational disadvantage (Ito, 1998) ‐ psychosocial issues: no difference NH vs UHL on social problem questionnaire (Culbertson & Gilbert, 1986)
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Efficacy of intervention across the lifespan: Hearing aids CROS aid Bone‐anchored hearing system (BAHS) FM (or DM)
AND
Adults School‐age children Infants/toddlers
Note: recommendations will vary for infants/toddlers versus school‐age and adults
Efficacy of intervention: Hearing aids School‐age children
Older studies (mostly school age); mostly parental report of benefit ‐ all severities: 26% regularly; 4% in school only; 50% never (Davis et el., 2001) ‐ moderately‐severe or better: 30‐81% regularly; 46% in school; 35% received services (Kiese‐Himmel, 2002; McKay, 2002; McKay et al., 2007) ‐ severe‐to‐profound: almost never (Kiese‐Himmel, 2002) ‐ children with UHL: less likely to wear hearing aids vs MBHL (Kiese‐Himmel et al., 2000)
Efficacy of intervention: Hearing aids Infants/toddlers Studies for 2‐3 yrs of age are very limited ‐ parent report; retrospective study (2‐17 yrs): found most received some benefit ‐ also parent report; children < 3 y: no detriment & no benefit described (McKay, 2002)
Note: no studies have investigated the optimal gain needed for infants/children with UHL ‐‐ current DSL[i/o] targets are for bilateral losses
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Efficacy of intervention: Hearing aids Infants/toddlers/school‐age Current approach: ‐ moderate‐to‐ severe (all ages): AC HAs recommended ‐ profound (unaidable): AC HAs not recommended (FM/DM for specific scenarios) ‐‐ as appropriate, assess benefit: speech perception, SIN, spatial hearing ‐‐ no adjustments made for fitting targets at this time (Bagatto et al., 2019)
Efficacy of intervention: CROS aid School‐age children
Limited information for benefits of CROS systems ‐ simulated UHL data: found CROS improved sentence recognition/story comprehension in noisy classroom compared to unaided & remote microphone ‐ most benefit when signal from side of a child/microphone used by talker in front of child (Picou et al., 2020) ‐ potential options: conventional CROS, transcranial CROS, BC on UHL side (headband/implanted at later age) ‐ in case of unaidable UHL (very poor speech discrimination), conventional CROS is recommended to avoid stimulating BC hearing (Bagatto et al., 2019)
Efficacy of intervention: CROS aid School‐age children Potential disadvantages/limitation: ‐ CROS does not improve binaural hearing so localization not improved ‐ partially occluding normal ear (**must check with earmold in place with real‐ear measures) ‐ CROS improves speech detection on UHL side in quiet ‐ BUT also can introduce noise to NH ear when, without CROS, head shadow would have reduced noise CROS aid not recommended for younger children because not able to control device for different listening conditions (McKay et al., 2008; Fisher & van Hyfte, 2016)
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Efficacy of intervention: Bone‐anchored hearing system (BAHS) Adults Results are variable & benefit small ‐ greatest improvement is seen when signal is on HL side & noise is coming from a different direction ‐ if the noise is on the HL side, noise from the BAHS is detrimental to speech recognition
Efficacy of intervention: BAHS Infants/toddlers Very limited data– only recently commonly recommended to fit conductive unilateral BC hearing loss (< 5 y not eligible for implanted BC device; 7‐8 y can qualify for implanted BC device) ‐ there are no fitting guidelines for fitting BAHSs for unilateral BC hearing loss in infants of different ages (or effects of fitting bilateral BC hearing loss with only one BAHS (current recommendation for BCEHP) ‐ Important to remember: ‐‐ infant vs adult BC physiological & behavioural threshold data support BC signal is more effective across frequency, particularly low frequencies, in infants compared to adults (Stuart et al., 1993; Stapells & Ruben, 1989; Small & Stapells, 2008; Hulecki & Small, 2011; Hansen & Small, 2012) AND ‐‐ interaural attenuation is greater for infants than adults (Yang et al. 1987; Hansen, 2010)
Efficacy of intervention: BAHS Infants/toddlers
Amplification in infants (correct fitting targets), intervention outcomes for fitting BC UHL, and decision re: fitting one or two BC devices for bilateral BC hearing loss, all need to be studied in more detail to guide clinical practice
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Efficacy of intervention: FM system (personal, desktop, classroom) Infants & children with UHL vs NH: poorer speech perception in noise & reverberation (e.g., Bess et al., 1986; Ruscetta et al., 2005) Limited research re: efficacy of FMs for infants/children with UHL; often mixed data with children with bilateral HL/special needs ‐ improved SNR for incidental learning important for early speech & language development BUT FM system could be detrimental in many listening environment ‐ e.g., when noise & signal on side with HL ‐‐ no improvement in the SNR (may ↓) & noise origina ng from affected side now directed to NH ear School‐age: FM system may be only useful device in classroom; provides best SNR improvement vs other devices (Updike, 1994; Tharpe et al., 2004;, Kentworthy et al., 1990) Bottom line: intervention “just not clear for any of choices” (Phonak 2016 panel, Bagatto et al., 2019)
Efficacy of intervention: CI Adults (post‐lingual) Review of sequential CI results (unilateral CI then bilateral CIs) ‐ R for 10 years: asymmetries in auditory system; activity more strongly lateralized to left hemisphere than normal; abnormal recruitment of different regions responsible for cognition, attention, multimodal integration & visual processing ‐2nd CI implanted: evoked atypical cortical responses with abnormally large widespread dipole activity (Jiwani et al., 2016)
Unilateral stimulation results in lasting asymmetries in auditory system, recruitment of additional areas to support hearing & no protection from auditory deprivation
Efficacy of intervention: CI Adults (post‐lingual)
How do adults do with CI for UHL? ‐ one challenge with this literature: different measures, different comparisons (UHL: CI vs HA vs BAHS; CI vs NH/NH occluded) ‐ overall, benefits are reported for CI ‐ 2 adult studies: 1) Arndt et al., 2017 & 2) Firszt et al., 2017 ‐‐ a few highlights re: results
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Efficacy of intervention: CI Adults (post‐lingual) signal (S) noise (N) NH UHL
1) Arndt et al. 2017 ‐ 85 adults; CI, CROS & BAHS– pre‐ and post‐op (12 mos) ‐ speech comprehension in noise *sig (CI) ‐ summation (signal & noise in front– S°N°) *sig (CI=BAHS) ‐ head shadow (signal to UHL; masker in NH ear) *sig (CI>all) ‐ localization (°) *sig (CI=CROS; CI> mono & BAHS) ‐ squelch (signal in front; noise to UHL) *same as monaural ‐ CI: no worse than mono (or better) ‐ NH: 3 dB benefit ‐ CROS or BAHS‐ decrement if noise routed to NH ear
Efficacy of intervention: CI Adults (post‐lingual) signal (S) noise (N) NH UHL
Arndt et al. 2017 cont’d ‐ no difference with duration of deafness ‐ 9h/day usage ‐ 48% word recognition ‐ subjective SSQ: spatial hearing & comprehension better than monaural; no difference in sound quality CI for post‐lingual UHL in adults is beneficial & better than BAHS or CROS
Efficacy of intervention: CI Adults (post‐lingual) signal (S) noise (N)
NH occluded
2. Firszt et al. 2017 ‐ adults with NH (listening unilaterally & bilaterally) & UHL NH NH ‐ adults with UHL pre‐ and post‐CI Binaural hearing measures: ‐ adaptive sentence understanding in diffuse restaurant noise; localization; NH UHL roving‐source SRT (different noise types & locations)
NH CI
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Efficacy of intervention: CI Adults (post‐lingual) signal (S) noise (N)
NH UHL 2. Firszt et al. 2017 cont’d CI ‐ NH better than UHL & less variable ‐ NH (1 occluded ear): better monosyllabic word recognition on occluded side than UHL (not on hearing side) ‐ some UHL w/o CI scored in same range as NH ‐‐ UHL localization better than NH with occluded ear (good side only): learned strategies to localize ‐ UHL & NH with occluded ear‐ no difference in speech in noise UHL with childhood exposure to monaural listening‐ localized better than NH (occluded ear), whether onset was in childhood or as adult, but had no greater effect on speech in noise Need to consider functional ability before CI considered
Efficacy of intervention: CI Adults (post‐lingual)
Always more research to do…recent research on adult bilateral stimulation (bilateral CIs, HAs & bimodal) ‐ found broader binaural pitch fusion for vowels vs NH (spectral distortion): slightly broader pitch fusion may improve localization but very broad fusion detrimental to speech perception in noise ‐ found large inter‐aural pitch mismatches: potentially illusion of lateralization when no ITDs or ILDs ‐implication: 2 ears not better than 1 (Oh, Reiss et al., 2016 & 2017ab) ‐‐ Fusion may affect ability to separate multiple sounds into segregated streams necessary to localize ‐‐ may explain variability in binaural benefits with CIs MORE RESEARCH needed…
Efficacy of intervention: CI Children (post‐lingual) ‐ found similar results compared to adults when post‐ lingual UHL in 4‐10 year‐old children (N=3) ‐ binaural hearing benefits for speech understanding in noise, localization ability & subjectively perceived hearing ability (Hassepass et al. 2013; )
Post‐lingual UHL– children or adults– similar results– CI improved localization, speech in noise & overall hearing ability…
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Efficacy of intervention: CI Children (pre‐lingual)
Does bilateral auditory stimulation result in restored spatial hearing in deaf children? ‐ investigated cortical representation of ITDs: NH children; deaf children with simultaneous bilateral CI implantation (<3.5 yrs) with 2 yrs of auditory experience (Easwar et al., 2017)
Bilateral simultaneous electrical stimulation is essential to protect bilateral auditory pathways from unilateral driven re‐organization BUT is not sufficient for normal development of ITD coding
Efficacy of intervention: CI Children (prelingual) signal (S) noise (N)
NH UHL Findings for pre‐lingual UHL with CI CI ‐ there are a small # of studies; these studies show the most common findings (a little bit of variability but much more research needed in larger groups) (Tavora‐Vieira & Rajan, 2015; Polonenko et al., 2017; Sladen et al., 2017, Thomas et al., 2017)
1) 5 cases of PRE‐LINGUAL UHL with CI tested at 12‐15 yrs (Firszt et al., CAA 2017 Ottawa conference): ‐ unlike post‐lingual CI group (~ to Arndt 2017), these PRELINGUAL UHL with CI showed: much lower CNC word test scores; poorer hearing in noise; no improvement in localization; very poor word recognition on CI side even with experience with NH ‐ some did not continue to use CI
Efficacy of intervention: CI Children (prelingual) signal (S) noise (N)
NH UHL CI
2) 1 PRE‐LINGUAL case of UHL: 8 yrs CI; BAHS/FM prior (Canete et al., 2017) ‐ CNCs, BKB sentences in noise (SN combinations), localization, questionnaires + CAEPs ‐ localization: CI>BAHS> no device ‐ speech in noise improved over time ‐ CAEPs immature 12 mos post implant
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Efficacy of intervention: CI Children (pre/postlingual) signal (S) noise (N)
NH UHL CI 4) 3 pre‐lingual UHL cases; 17 mos, 4.5 & 6.8 yrs AND 1 post‐lingual case; 9 yrs (Tavora‐Vieira & Rajan, 2015) Pre‐lingual: ‐17 mos: uses CI except when loud; no other measures available ‐ 4.5 yrs: does not use CI & no measures available ‐ 6.8 yrs: cannot discriminate words with CI alone; no improvement in speech in noise or localization; wears for “fullness of sound” post‐lingual: substantial improvement in speech in noise & localization; wears CI regularly Pre‐lingual outcomes poorer than post‐lingual
Efficacy of intervention: CI Children (pre/postlingual) signal (S) noise (N)
NH UHL CI
5) 1 PRE‐LINGUAL case study (Gifford, panelist for Phonak 2016 conference) ‐CI for UHL: ‐ very poor word recognition scores ‐ Mom disappointed but unexpected benefit‐‐ child preferred music with CI + NH – wore all the time
What is success? Watch for future infant/child research in this area!
TOPIC AREAS TO BE ADDRESSED Prevalence of UHL Loss of binaural hearing benefits with UHL‐‐ effects on spatial hearing + other consequences Review of current data re: intervention for UHL across the lifespan: infants to adults Bone‐conduction hearing loss: Unilateral & binaural
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Bone‐conduction hearing loss: Unilateral & binaural
Start with a review of BC hearing in adults & infants…
Not as simple as < 10 dB of inter‐aural attenuation (IA) for a BC signal independent of age…
Some review of adult AC IA… AC
AC binaural hearing (adult) ‐ ITDs & ILDs depend on separation of signal received at 2 ears: IA 55‐85 dB depending on transducer (insert > supra‐aural) & pinna effects (lesser degree) ‐ inter‐cochlear delay: max of 0.66 ms ‐ minimum inter‐cochlear delay to resolve ITDs: 0.20 ms ‐ AC binaural processing of ITDs: min of 0.01 ms (e.g., Stenfelt, 2012; Reinfeldt et al., 2013)
Some review of adult BC IA… BC
BC binaural hearing (6 years +) ‐ IA: 0‐10 dB at 500‐2000 & > 5000 Hz; 10‐17 for 3000‐5000 Hz (e.g., Stenfelt, 2012; Reinfeldt et al., 2013) ‐ ITDs & ILDs depend on separation of signal received at skull to 2 cochleae (IA 0‐17 dB) & small head shadow effect ‐ low BC IA results in summing of signals at cochlea so binaural processing more central to left & right cochleae ‐‐ less effective ‐ inter‐cochlear delay: 0.30‐0.50 ms > 1000 Hz (cadaver head)
BC binaural benefit ≈ ½ AC binaural benefit (adults)
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What about infant AC & BC binaural benefit? • Maturation of the Skull & Tissues Tabular (adult) • Skull ‐ Increase in head circumference ‐ Change in structure of skull bone ‐ Maturation of sutures and fontanelles Unilaminar (infant)
www.medicalhistology.us/
dermatologic.com.ar/ • Skin & Subcutaneous Tissue www.oganatomy.org/ ‐ Increase in thickness and density (collagen, elastin) Substantial differences in infant vs adult skull
Slide borrowed/modified from A. Mackey M.Sc. thesis defence
IA of AC stimuli in infants Surprisingly, no published infant data Probably similar to adults with some age‐ & frequency‐dependent differences IA of BC stimuli in infants Only indirect infant estimates available:
Study Method Indirect measure Age IA(dB)
Yang et al 1987 ABR clicks Wave V latency Adult 0‐10 Neonate 25‐35 12 months 15‐25 Small & Stapells ASSR‐ AM/FM Ipsi/contra Adult 0‐10 2008 500‐1000 Hz Fc asymmetries 0‐6 months 10‐30 Hansen 2010 ASSR‐ AM/FM Effective masking Adult 0 (M.Sc. Thesis) 1000 Hz levels (Binaural AC)
0‐7 months 10‐15 10-35 dB depending on age of infant
Infant BC & AC IA – decisions re: devices ‐ it is now recognized that BAHS should be fitted in cases of monaural conductive UHL (& SNHL depending on degree of loss) ‐‐ BCEHP recommends this! ‐ recommendations for bilateral conductive– currently, BCEHP recommends fitting monaural instead of binaural BC devices ‐‐ monaural fitting for binaural loss creates a UHL! ‐‐ adult vs infant approach– perhaps should be different: infants have larger BC IA values depending on frequency compared to adults (indirect estimation) ‐‐ fit binaural BAHS in infants to avoid creating a UHL? An aside: some clinicians who fit devices for infant bilateral atresia, US & Canada, report infants benefit from bilateral BAHS device fitting‐‐ at this time, only monaural BAHS fittings are offered by BCEHP‐‐ may need to reconsider this policy as more data collected???
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BCx
Estimates of BC IA using sound pressure in ear canal in infants & adults attempted (i.e., not direct measures of IA) ‐ 0‐2 yrs > adults ‐‐‐ but less than expected compared to other BC IA estimates (Mackey et al., 2017) ‐ adults ‐‐‐ sound pressure estimates vs direct measurements in profound UHL cases ‐‐ significant differences found at 500, 750, 2000 & 3000 Hz (Reinfeldt et al., 2013) ‐ new information suggests NOT ACCURATE to use sound pressure in ear canal to estimate IA in infants or adults (Note: recommended in past by Hodgetts & others – no longer) Direct BC IA estimates needed for infants, similar to foundational research for adults
BC AC AC binaural hearing (infant) – we know a little ‐ more similar to adults at level of brainstem vs auditory cortex e.g., brainstem binaural interaction component present in some babies‐‐ less robust than adults (e.g., Cone‐Wesson et al., 1997; Furst et al., 2004) ‐ can detect ITDs similar to adults at level of cortex but immaturities (Small, Ishida & Stapells, 2016) ‐ Behaviourally: immaturities until 4‐5 years of age (e.g., Nozza et al., 1998) BC binaural hearing (infants) ‐ not much known about infants PREDICT: Based on current indirect estimates, greater BC binaural benefit compared to adults (greater inter‐cochlear delay) but less versus AC stimulation
ADULTS Binaural benefit of bilateral BAHS in NH adults ‐ interesting study: BAHS for bilateral conductive & UHL profound SNHL (Stenfelt, 2005) ‐ model of binaural hearing: head‐related & skull vibration transfer functions ‐ bilateral BAHS had clear binaural benefit: > stimulation level, better directional hearing & space perception, & better speech perception in noise ( Important question: Why unilateral BAHS for infants then‐‐ recent recommendation by BCEHP??? ‐‐ actually quite common for infants with bilateral atresia to benefit from BAHS bilaterally (personal communication to S. Small at conferences‐ local & international!) 20 2020-09-29 ADULTS UHL with BAHS: harder to predict outcomes ‐ the > BAHS gain needed to cross skull, the lower the input level at which BAHS saturates ‐ great variation in BC IA across studies & individuals: ‐ high BC IA: no benefit with BAHS (infants???) ‐ low‐mid IA & good SNR on UHL side: benefit with BAHS but only if S & N spatially separated & S on UHL side (3‐5 dB) ‐ if IA = 0 dB: BAHS beneficial (5 dB for .8‐4 kHz; >10 dB for 1‐2 kHz) ADULTS: Binaural benefit of bilateral BAHS in NH adults (Zeitooni et al., 2016) ‐ BC stimulation at Spatial benefit between positions typical BAHS position AIR BONE ‐ measures of binaural Spatial release 8.4 dB 4.0 dB processing for bilateral from masking Binaural 6.6 dB 4.7 dB BAHS vs AC intelligibility level difference Binaural masking level difference: S°N180° 7.5 dB 2.5 dB S180°N° 9.4 dB 4.6 dB Lateralize to leading side Precedence Effect ≥ 0.5 ms BAHS position: ≥ 40 ms Low & High Mastoid position: ≥ 10 ms Variability BC > AC Binaural processing is present for bilateral BAHS when cochlear function is available but less than AC hearing Underlying broader questions re: UHL Is auditory input to the ear with hearing loss always better than no auditory input for brain plasticity & function? ‐ yes, in many cases of post‐lingual UHL (CI mostly best choice) ‐ need full evaluation of speech‐in‐noise, localization, etc. ‐ need more data on pre‐lingual UHL: benefits of CIs & other devices Do devices restore binaural hearing? ‐ CI > BAHS or CROS for UHL for restoring binaural hearing but very variable & may depend on pre‐ vs post‐lingual binaural experience ‐ BAHS for conductive UHL likely restores BC binaural benefit (more so in infants???) based on bilateral BAHS data (~1/2 of AC benefit) ‐ BAHS for sensory UHL only beneficial if low BC IA (some S/N positions) 21 2020-09-29 Underlying broader questions re: UHL How do we explain variability in binaural benefit with devices? ‐ need appropriate battery of binaural hearing measures & a lot more data across ages & auditory experiences UHL Protocol Update (BCEHP provincial meeting 2017; BCEHP updates) Recent change: Consider amplification to avoid potential delays ‐‐ past, UHL cases were monitored due to limited evidence of delays in majority of UHL cases New approach since 2017/2018: Criteria: Minimal < 30 dB HL pure tone average (PTA)* Aidable 30 ‐ 70 dB HL PTA Severe‐ Profound > 70 dB HL PTA + Monitoring of hearing and development *PTA rather than thresholds @ specific frequencies UHL fitting recommendations: Minimal (< 30 dB PTA) Monitor hearing Refer to early intervention for monitoring Do not fit amplification - Limited evidence of benefit Aidable (30‐70 dB PTA) ** newly implemented by BCEHP Provide hearing aid to improve binaural hearing Factors to consider ‐ Age of amplification? Speech understanding (if measurable)? Severe/Profound (> 70 dB PTA) Note: in cases of bilateral Limited potential binaural hearing atresia (NH via BC), BCEHP recommendation is for one Binaural interference? BAHS only. Potential query CROS not supported in BCEHP re: this decision: now ‐ overcome head‐shadow effect inducing a unilateral hearing loss; effect on brain ‐ limited evidence in population of the plasticity?? program 22 2020-09-29 UHL follow‐up Summary Frequent audiological evaluations ‐ Adjust amplification as hearing changes Counseling needs: ‐ Parents and child ‐ Uncertainty ‐ Etiology ‐ Progression Cochlear implantation? Thoughts? REVIEW MEDICAL INFORMATION on your own time: summarized in Appendix!! Appendix Medical considerations for UHL ‐‐ courtesy of Judith Lieu (ENT) Annual audiogram and follow‐up ~20% will progress to bilateral/asymmetric ~40% will progress in UHL ear 23 2020-09-29 Etiology—Sensorineural I Etiology—Sensorineural II Temporal bone abnormalities ~33% overall Acquired ‐ increased incidence with severe‐to‐profound • CMV: 1/3 with congenital CMV have UHL UHL • Meningitis—Pneumococcal, H. flu, etc. • Enlarged vestibular aqueduct • Labyrinthitis • Cochlear nerve aplasia/hypoplasia • Ramsey‐Hunt (herpes zoster oticus) cochlear dysplasia (e.g., incomplete partition) • Trauma: temporal bone fx, concussive • Vestibular malformations • Surgery: otologic, neurosurgical • Narrow internal auditory canal • Meds: aminoglycosides, cisplatinum Etiology—Sensorineural III Genetic Syndromes Etiology— neural & other • Pendred (Mondini malformation, EVA, • Unilateral ANSD euthyroid goiter, SLC26A4 gene) • Brainstem or cerebellar tumors • Waardenburg syndrome • Schwannoma / acoustic neuroma • Goldenhar syndrome (hemifacial microsomia) Etiology—Conductive UHL • Klippel‐Feil • Temporary: otitis media, cerumen • CHARGE • Aural atresia (absent ear canal) • VACTERL (vertebral, anal, cardiac, tracheoesophagus, renal, and limbs) • Tympanic membrane perforation • 22q11.2 (DiGeorge, velocardiofacial, etc.) • Chronic suppurative otitis media Familial EVA, cochlear n. aplasia • Cholesteatoma • Genetic mutations associated with bilateral • Ossicular malformations hearing loss are rarely present in UHL • Otosclerosis • Tympanosclerosis Medical Work‐up of UHL Imaging of Sensorineural Hearing Loss • Complete history Temporal bone CT • Prenatal, perinatal, postnatal • Inner ear bony malformations • Family history Temporal bone MRI • Imaging – CT, MRI • Inner ear soft tissue malformations • Lab testing – urine, blood • Abnormalities of the cochleovestibular • EKG (VIIIth nerve) • Consultation – Ophthalmology, Genetics • Screens for major brain abnormalities Brain MRI Physical Exam • Neurologic / cognitive concerns • General appearance • Conditions that affect the brain (CMV, • Anatomic or neurologic abnormalities syndromes) • Head and neck exam • Temporal bone MRI suggest • Dysmorphic facial features abnormality • Pigmentary abnormalities • Neck masses, pits/tags • Ear exam • Microtia, anotia, auricular pits/tags • Cerumen, vernix, blind pouch, aural atresia • AOM, OME Temporal bone CT: 18% to 43% positive findings Temporal bone MRI • labyrinthitis ossificans • up to 48% positive findings for • enlarged vestibular aqueduct severe‐to‐profound UHL • Mondini deformity (cochlear hypoplasia) • Rule out intracranial tumors • labyrinthine dysplasia • Cochlear nerve aplasia/hypoplasia • dilated semicircular canals • narrow IAC • Narrow cochlear nerve canal CT scans vs. MRI • CT: Greater % enlarged vestibular aqueducts, vestibulocochlear abnormalities • MRI: Greater likelihood of cochlear nerve and skull base/intracranial abnormalities identified Considerations • Radiation dose with CT • Sedation with MRI 24 2020-09-29 Urinalysis Consultations • CMV (congenital CMV infection) Ophthalmology • Hematuria ± proteinuria (Alport & Epstein • Up to ½ of children with syndromes) bilateral severe SNHL have • ↑ Calcium excre on & alkaline urine (renal ocular findings, most tubular acidosis) commonly refractive errors • Glycosaminoglycans (mucopolysaccaridosis) • Optimize vision when hearing Blood tests is suboptimal • CBC Genetic • risk of thalassemia or sickle cell disease ‐ Syndromic • Macrothrombocytopenia & leukocyte inclusions in Fechtner o Waardenburg syndrome (associated with Alport syndrome) o Usher • Urea & electrolyte abnormalities with renal dysfunction ‐ Familial • Alport syndrome • Specific immunoglobulins • Rubella, HSV, syphilis, CMV Thyroid tests • Thyroid function in congenital or acquired hypothyroidism • Perchlorate discharge test for Pendred syndrome Autoimmune work‐up • ESR • anticardiolipin antibodies • immunoglobulins • complement studies 25