ABR - Thresholds Flashcards
What are 5 reasons to have an early screening program (for any disorder)?
- importance of the disorder’s prevalence
- diagnosis of condition
- treatment resources for condition
- responsiveness to treatment
- advantages of early intervention
What deficits are hearing impaired infants at risk for?
- speech/language problems
- academic issues
- social and emotional development problems
How long has the ABR been a part of NBHS procedures?
since 1980
What health bodies came together to develop a mandatory, universal NBHS program?
NIH, American Academy of Pediatrics, and JCIH
What is the purpose of the Early Hearing Detection and Intervention (EHDI) program statewide?
- to ID every child born with a permanent HL
- before 3 months old
- provide appropriate intervention services before 6 months old
- family support/medical home
- hearing screening tracking
- data management systems for public health info
What factors are used in every single NBHS?
- sensitivity (low false negatives)
- specificity (low false positives)
- cost
What consists of the JCIH 2019 guidelines for NBHS?
- use either automated OAEs or automated ABR
What OAE protocols are used for NBHS?
- transient OAEs
- distortion product OAEs (influenced by outer and middle ear problems)
When should we not use OAEs as a screening measure for newborns?
when they’re in the NICU (because they can be at higher risk for ANSD, and OAEs don’t catch this)
What is tested with the ABR during NBHS?
peripheral auditory nervous system and the brainstem
When should ABR screening be recommended for newborns?
when they’ve spent at least 5 days in the NICU
Babies in the NICU are more at risk for what conditions?
- ANSD
- late-onset progressive HL
Babies/infants with neuropathy will…
pass their OAE screen, but fail their ABR
What is the JCIH’s guideline for rescreening?
a single repeat screen should be conducted if the infant doesn’t pass their initial screening before they’re discharged (preferably several hours after the first)
When should NBHS be performed?
6 hours after birth, but better to do closer to discharge time (this reduces referrals)
How many NBHS can be performed before discharge of the baby?
- 2 high quality (asleep or resting quietly) before discharge
How many NBHS can be performed post discharge of the baby?
one, before referral to a pediatrician
When should NBHS be done for babies born in a birthing center?
in the first 2 weeks of life
If a baby is born with congenital atresia, what should be done?
refer for complete audio logic eval rather than doing screening
What is the NBHS protocol when using OAEs?
- TOAEs: broadband responses from clicks
- DPOAEs: fx-specific response from a nonlinear tone pair
What are some disadvantages of using OAEs for NBHS?
- the state of the outer/middle ear can influence results
- info on IHCs or auditory nerves not obtained
- can cause high referral rates and high quantity of false-positives
The use of ABR for NBHS exhibits a…
lower susceptibility to ME pathology, and a higher ability to detect retro-cochlear impairments
What is the clinical sensitivity and specificity for ABR?
100% sensitivity
97-100% for specificity
What consists of the pass/fail criteria for hearing screenings with ABR?
- pass = presence of wave V
- fail = absence of wave V
What is the protocol for hearing screenings with ABR?
- click stimulus
- presentation level of 35 dB nHL (for confirming normal hearing or mild HL)
- presentation level of 70 dB nHL (for determining greater HL) if failed at 35 dB
- repetition rate of about 23-37 clicks
What is the JCIH recommended protocol for hearing screenings (2019)?
- 2-stage screening and rescreening with either OAE or A-ABR before hospital discharge
What does the JCIH suggest to do if the baby doesn’t pass the initial A-ABR?
re-screening should be done using A-ABR again because persistent transient ME problems may decrease the sensitivity of OAE
The 2019 JCIH guidelines recommend A-ABR for which situations?
screening and re-screening of NICU infants (due to their higher risk for ANSD)
The 2019 JCIH guidelines recommend what for babies who don’t pass their A-ABR?
be referred to an AuD for re-screening, and complete a full ABR is needed
The 2019 JCIH guideline recommends what for when a child fails their discharge screening?
- post discharge screenings should 1, performed asap or within a month
- failure on this re-screening in one or both ears = a complete diagnostic ABR eval
What are some perinatal risk factors for hearing loss (JCIH, 2019)?
- early, progressive, late-onset permanent childhood HL in family history
- more than 5 days in the NICU
- hyperbilirubinemia w/ exchange transfusion (regardless of length of stay)
- more than 5 days of amino glycoside administration
- asphyxia or hypoxic ischemic encephalopathy
- extracorporeal membrane oxygenation
- in utero infection (herpes, rubella, syphilis, toxoplasmosis, or cytomegalovirus
- mother + for Zika, while infant exhibits no symptoms/clinical findings
- mother + for Zika, with infant exhibiting symptoms/clinical findings
- mother + for Zika, with infant exhibiting no symptoms, but displays clinical findings
- birth conditions (microtia, atresia, ear dysplasia, oral/facial cleating, white forelock, microphthalmia, microcephaly, congenital/acquired hydrocephalus, temporal bone abnormalities
- presence of one of over 400 syndromes characterized by atypical hearing thresholds
What are some perinatal and postnatal risk factors (JCIH, 2019)?
- positive cultures for infections linked to SNHL (confirmed bacterial and viral meningitis or encephalitis)
- events that result in HL (significant head trauma or chemotherapy)
- concerns by caregivers in terms of hearing, speech, language, developmental delay, and/or developmental regression
When does the JCIH recommend a diagnostic eval to confirm the presence/degree of HL for babies?
when they don’t pass the 2 stages of screening
What can be used for fx-specific threshold estimation before the baby is 2-3 months old?
- ABR or ASSR to determine type, degree, and configuration of the HL
- use tone bursts or chirps as stimuli
- intervention should between 3-6 months
Fx-specific stimuli for ABRS are ideal for what?
to ensure that ABR thresholds reflect the pure tone audiogram (represents the primary activity in the cochlea restricted to a specific place corresponding to the fx, rather than a broad area like with chirps and clicks)
What type of stimuli does the JCIH (2019) recommend for estimating AC thresholds through ABR and ASSR?
fx-specific (tone bursts/chirps)
ABR thresholds can overestimate or underestimate what when measuring?
- can overestimate behavioral thresholds with normal hearing
- can underestimate behavioral thresholds with HL
What causes the discrepancy between ABR thresholds and estimation?
- the differential effects of stimulus duration due to reduced temporal integration of behavioral and ABR thresholds
Estimating BC thresholds with fx-specific tone bursts/chirps can be used to what?
- accurately quantify the magnitude of the conductive components and to differentiate normal vs impaired cochlear sensitivity in infants with conductive, mixed, or SNHL
What indicates a conductive HL when using ABR to estimate thresholds?
if the AC-ABR is elevated in the presence of normal BC-ABR thresholds
What indicates SNHL when using ABR to estimate thresholds?
if both the AC and BC-ABR thresholds are elevated
Estimating BC thresholds with fx-specific tone bursts/chirps can be used to what?
to accurately quantify the magnitude of the conductive component and to differentiate normal vs impaired cochlear sensitivity in infants with conductive, mixed, or SNHL
Obtaining BC thresholds are essential for?
estimating additional HA gain and output in the presence of conductive HL
Fx-specific chirp stimuli elicit…
larger wave V amplitudes compared to traditional click and fx specific tone burst stimuli
Fxs and intensities of stimuli used for estimating BC-ABR thresholds are…
- fxs: most studies limited to 500-2000 Hz
- intensities: most clinicians use 30 and 20 dB nHL as normal levels for 500 and 2,000
First step for estimating AC and BC thresholds with ABR
- start with AC
- start with 2k Hz (important for speech and psychoacoustics) tone burst and replicate using a starting level equal to the minimal level of 30 dB nHL
ABR-AC and BC threshold estimation procedure:
- if response isn’t clear at minimum level and is inconclusive, obtain 2 responses at 10 dB above the minimum level
- if response is present: the 10 dB level is the upper bracket for the threshold, and threshold would be between 30-40 dB nHL
Once you obtain a 2k Hz threshold for one ear, what does the protocol say to do?
switch to opposite ear and repeat procedure
After switching to opposite ear and repeating procedure at 2k Hz, what is next?
- obtain bilateral responses for 4k Hz (this fx is quicker because responses are more robust and clearer)
- then obtain bilateral responses for 500 Hz
What is done if no AC-ABR response is obtained at the minimum level (30 dB)?
- obtain a response at 60 dB and continue to 80 dB
- now beginning to suspect HL (need to determine type)
Do you need to remove inserts to obtain BC thresholds in infants?
no - the occlusion effect doesn’t occur in infants
What do you do if both AC and BC-ABR thresholds are elevated?
switch to BC-ABR threshold search and bracketing at 500 Hz (minimum level 25 dB) before shifting to 4k Hz
- if a conductive component is found at 2k Hz, it might not be necessary to obtain accurate estimate of BC-ABR threshold at 500 Hz (you can expect the presence of a conductive component at 500 Hz)
- BUT, the presence of a conductive component at 500 Hz can’t rule out a possible SNHL component at 2k Hz
If the AC-ABR at 4k Hz is the only fx showing an elevated threshold, then what else has to be obtained?
BC-ABR threshold estimates for that fx
When are AC-ABR threshold estimates at 1k Hz required?
ONLY if the difference between AC-ABR thresholds in dB nHL is 25 dB
A 5 dB final bracketing step is recommended for when?
when the ABR threshold estimates are greater than 70 dB estimated hearing level
Response detection criteria legend
- TH: threshold
- RP: response positive
- NR: no response
- INC: inconclusive response
When is the RP considered a TH?
when the RP and NR are separated by 10 dB
What is needed for there to be “no response”?
requires an RP at a 10 dB higher level as a reference, and essentially flat replicated tracings of at least 1k sweeps at a level 10 dB below
How do we derive the estimated hearing level (dB eHL)?
by applying correction factors determined from a normative statistical relationship between ABD and behavioral thresholds
What does the Eclipse software correction factors include?
- 20 dB at 500 Hz
- 15 dB at 1k Hz
- 10 dB at 2k Hz
- 5 dB at 4k Hz
What is the typical masking stimulus used for ABR?
white noise since clicks are a broadband stimulus
How much masking noise is needed for ABR?
it has to be enough to elevate the hearing threshold in the non-test ear in order to prevent cross-over of sound
AC-ABR masking criteria:
- no masking needed if absolute latencies of waves I, and V are normal
- if these latencies are abnormal, masking is needed
BC-ABR masking criteria:
- not required if wave I is present at normal latencies
- required if wave I is delayed or absent
