Special Cases and Hearing Aid Programming Alternatives Flashcards
Does binaural summation and squelch require fusion of the signals delivered to the ear?
Yes
Must be within 15 dB of each other
ILD’s must be maintained by HF audibility above 3k Hz
ITD’s are maintained by LF audibility below 850 Hz
Do patients with asymmetric losses benefit from bilateral amplification?
Yes
Even though they may not fully enjoy the binaural advantage
What defines an asymmetric loss?
3 adjacent frequencies of > 20 dB
1 frequency > 25 dB
Asymmetric speech intelligibility
Asymmetric SNR loss (20% difference)
Asymmetric LDL
What are some things to consider when fitting an asymmetrical loss with bilateral amplification?
Consider each ear’s contribution to speech intelligibility
Consider the amount of useful audibility attainable in each ear (realistic and verifiable)
There are multiple studies that demonstrated some binaural advantage in case of asymmetry
Fitting asymmetric losses requires careful performance monitoring to ensure binaural interference is not occurring
When should you only aid the better ear (CROS or BiCROS)?
Word recognition is extremely impaired on the poor ear
Loudness sensitivity limits the ability to provide useful function
Signs of binaural interference are present
(if any one of these occur)
When would you aid the poorer ear only to balance signal audibility and supply some binaural benefit?
The better ear has near normal thresholds in critical speech ranges
When would you fit both ears (asymmetric loss) and let the patient experience and determine the value of binaural amplification?
If both ears may assist speech intelligibility to some degree
What are some fitting strategies for bilateral devices?
Fit devices on separate days
Try different combinations (one device or the other or both)
Fit the better ear first (relying on this ear for communication)
Fit the poorer ear second (only done once the fitting on the better ear is optimized, increase output to an intensity that supports intelligibility without interference)
Slowly introduce use of bilateral devices in noise
How do you determine the best prescriptive formula for the patient?
May need to try more than 1
Create memories with different formulas for patients to try in real world (may require manually programming memory to fitting targets)
Use a formula that is best suited for a severe loss when needed (NAL-RP)
Don’t worry if you don’t meet a “target” for the entire frequency range (simply providing some useful info to aid localization)
What questions should the audiologist answer before fitting an asymmetrical hearing loss?
Is the use of any amplification appropriate and the best option for this patient?
Is the patient adequately able to communicate in real world settings with this option?
Is there a better solution than a hearing aid?
Should you discuss realistic expectations of benefits and limitations (of binaural amp with an asymmetric loss) with the patient?
Yes
Conduct unaided/aided unilateral/ aided assessments and share comparative test data
What are some alternative options for patients with asymmetrical losses?
CROS
BiCROS
AmpCROS
Bone-anchored implantables
CI
Remote mic
What is a CROS?
Contralateral routing of the signal
If patient desires improved hearing when one ear is close to normal and the other is unaidable
Lacks binaural benefit
What is a BiCROS?
Bilateral contralateral routing of signal
If better ear has reasonable SNR loss and can benefit from ear level device using directional microphones
Lacks binaural benefit
What is ampCROS?
Combines traditional & CROS hearing aid features
Output is delivered to the poorer ear and routed to the better ear
Requires some degree of speech intelligibility in the poorer ear
May supply some binaural benefit
Many audiologists are moving away from it
How is CROS verification done?
Probe tube is placed on the better ear
Patient position: rotates to 45 degrees azimuth during testing (better ear closer to the speaker)
Audioscan is set to OPEN fit to prompt equalization of a STORED CALIBRATION signal (avoid reference mic contamination)
How do you set up the audioscan for CROS verification?
Select “Single View”
Select the better ear as the test ear
Click on the “Audiometry” button and select “None” as the target rule
Enter a threshold to start test
How should you measure an REUR on a CROS?
Place BOTH Right and Left probe modules on patient (only insert probe in better ear)
Set style to BTE
Measure REUR with 65 dB SPL speechmap signal
How do you measure the head shadow with a CROS?
Rotate patient position so POOR ear is @ 45 degrees azimuth
Change style to CROS hearing aid
Repeat measurement of 65 dB SPL SpeechMap signal
Note LTASS/speech envelop difference
How do you measure CROS effect?
Device set up for CROS
Patient still 45 degrees with the better ear toward the speaker
How do you verify BiCROS fittings?
Style: CROS
Follows standard verification protocol for prescriptive targets are added for the better ear (fitting better ear just like an other HA)
Position patient @ 45-degree azimuth to poorer ear
Dynamic range compression at 55-, 65-, and 75-dB SPL and MPO settings are verified “better ear”
What is a transcranial CROS?
Rare, but you might encounter it
Places an air-conduction signal in the bad ear that is loud enough that it crosses over via bone conduction to the good ear (means only one hearing aid need be worn)
What losses were DSL and NAL designed to fit?
Classic mild to moderate SNHL
The prescribed fitting parameters don’t work well for patients fall out of line with the “classic” hearing loss profile (NIHL, cochlear dead regions, reverse slope loss, severe to profound thresholds, conductive loss)
What is the verification for NIHL focused on?
Audibility of residual hearing within healthier regions of the cochlea
What are the 3 types of NIHL?
Type 1 - few years of exposure, normal or near normal 2kHz, special fittings aren’t necessary
Type 2 - many years of excessive exposure, threshold loss extends to LF (below 2000 Hz), use of typical fitting strategies may be helpful if the output supplies HF audibility
Type 3 - extreme cases, hearing is near normal for LF only, thresholds shows a precipitous slope, special fitting strategies needed
What are some challenges associated with type 2 and 3 NIHL?
Outer hair cell (OHC) damage in the cochlea leads to abnormal loudness growth (recruitment)
Potential distortion for patients with damaged or absent inner hair cells (IHC) - Dead regions
High frequency output is limited by feedback
WRS test may not accurately reflect patients ability (cannot make signals loud enough for effective testing)
Full HF audibility is not a reasonable goal due to comfort and sound quality
What are the old theories for cochlear dead regions?
Assume the presence of dead regions for thresholds >70 dB HL
Assume the presence of dead region for precipitous slopes >20 dB/ octave
Would not perform TEN test
Avoid adding gain to any frequency meeting these criteria
What does the current research about dead regions suggest?
Evidence finds dead regions are present in only 1/3 of individuals with hearing loss
Dead regions may be present at levels as low as 55 dB HL
Prevalence increases with only a 10 dB slope in 2-4KHZ region
Most individuals only have 1-2 dead regions frequencies (only 3% of patients with dead regions have extensive dead regions) - more than 3 regions
TEN test not necessary for all patients
Are special fitting strategies needed for patients with the presence of 1 to 2 dead regions?
No
Are special fitting strategies needed for patients with extensive dead regions?
Maybe
Do not assume this individual needs reduced high frequency output
Patients appear to benefit from HF gain if only 1-2 dead region frequencies between 1-4k Hz are present
2/3 of patients with “extensive dead regions” (> 3 DR’s) PREFERRED high frequency audibility (pull away HF output if the patient is not liking the sound)
How do you choose a receiver for a patient with a severe sloping loss?
Focus on supplying gain to heathier areas of the cochlea in the low and mid-frequencies
There’s no need to select a receiver offering wider frequency responses with extended high frequencies
What are some fitting strategies for type 3 NIHL?
Add gain to thresholds below 85 dB HL
Strive to achieve a balance audibility from 500 Hz up to 3k Hz for thresholds below 85 dB HL
Add 5-8 dB of gain to normal thresholds just before the precipitous drop (benefits sound quality)
Enable expansion to reduce mic noise when hearing is near normal below 2k Hz
If a threshold is near LDL, apply no gain or 1/5 the threshold (20% of threshold vs. 46%)
What are some additional fitting considerations for those with type 2 or 3 NIHL?
Automatic directional mics enhance intelligibility (minor improvements to SNR can increase intelligibility)
Avoid too many compression ratios (reduces spectral contrasts between vowels and consonants - smooth increase rather than abrupt)
Select brands using true phase cancellation DFS (preserves HF output by adding as much as 10 dB of gain)
Increase ear canal length to increase output and decrease occlusion effect
Study up to here for the midterm
When should frequency lowering be enabled for the adult population?
4-6 weeks after initial fit
Understand the brands signal processing algorithm before enabling it
Verify FL output to ensure speech information moves to audible region w/o unduly limiting bandwidth of the entire signal
Validate effectiveness with objective measures & self report questionnaires
Which manufacturers use frequency compression?
Phonak, Unitron, Signia
What manufacturer uses frequency transposition?
Widex
Which manufacturers use spectral warping?
Starkey, Oticon, Bernafon
What losses is FL beneficial to?
Steeply sloping loss
Severe to profound loss
What is our goal behind FL?
Fine-tune to the weakest possible setting for improved audibility
What can result from FL?
Improve detection of high frequency speech sounds
Improve discrimination of S from SH, particularly after a period of acclimatization
Increase activity in auditory cortex for high frequency stimuli
Settings stronger than this are associated with diminished sound quality
What is the maximum audible output frequency (MAOF)?
Used when programming FL (FL turned off during this test)
Maps the region where audibility ends
Lower limit- the frequency where the LTASS becomes inaudible
Upper limit- the upper range frequency where the speech envelope becomes inaudible
How do you assess FL candidacy?
Disable digital noise reduction
Signal: calibrated /S/ presented at 65 dB SPL
Verify audibility: when the upper shoulder of the MOAF is audible with a DISABLED Frequency lowering
Enable Frequency lowering to verify if audibility of a calibrated /s/ input signal is achievable
Adjust until the upper shoulder is audible by about 10 dB
Ideally, an “SH” signal is 100 Hz lower than the “S” (used as a check)
Is verification of spectral warping different?
Yes
It copies the original HF signal and transposes it to the lower frequencies
Observe both humps on graph
Is there an increased prevalence of LF IHC loss with reverse slope loss?
Yes
Do dead regions exist with reverse slope SNHL?
Yes
What do the fitting strategies for reverse slop losses focus on?
Audibility within residual hearing regions (healthier regions of the cochlea)
What leads to unsuccessful fittings for reverse slope losses?
The addition of too much gain in low frequencies leads to upward spread of masking
Satisfaction may be limited due to increased likelihood of extensive dead regions (>3 DR) (no frequency raising)
How do you fit reverse slope losses?
Add only 15-20 dB of gain in low and mid frequencies initially
Add 10-15 dB at 2k Hz & above of gain for increased audibility (even at normal thresholds)
Allow time for habituation before further increase (some may want more LF gain and some may need less)
Add gain to the MF and be cautious when adding LF gain
Modify HF gain based on individual perceptions
Is additional gain needed to overcome the attenuation caused by mechanical loss?
Yes
Air/bone gaps attenuate the signal’s amplitude before it arrives to the cochlea
Do you need compression when fitting a loss with ABGs with normal BC thresholds?
No
Compression is not needed because the dynamic range is normal
Use of 1:1 linear signal processing (or very low CR) is fine
Do you need compression with a mixed loss?
Yes
Compression is needed in addition extra gain due to the reduced dynamic range
How do you calculate additional gain for a loss with an ABG?
Calculate prescriptive gain recommendation for AC threshold
Calculate 25% of A-B gap. This additional gain is added to the AC prescriptive targets
Increase MPO by the same percentage used for A-B gap calculation allowing headroom for the extra gain
Do NAL formulas automatically calculate the ABG?
Yes
Provides this calculation when the BC thresholds are entered into the verification unit
DSL 5.0 does not compensate for additional gain needs
Do all of the fitting software algorithms include the adjustment for ABG?
Maybe yes, but maybe no!
Each brand you use must be evaluated to identify potential limitations
What threshold loss will result from a small perf (1-2 mm)?
Minimal hearing loss
What threshold loss will result from a larger perf?
25-35 dB CHL
What threshold loss will result from a total TM perf?
About 40 dB CHL
What threshold loss will result from a posterior-superior with ossicular erosion?
Could be a loss as great as 60 dB
What are some options when perfs are present?
Bone conduction/bone anchored devices
Ear level devices (might vary recommendations based on if it’s a dry perf or wet perf; might need airflow)
Can you think of the severe to profound SNHL as a whole?
No, you need to consider how they obtained their loss
They are all different and should be treated that way
Residual hearing in this population varies significantly from patient to patient
There may be mechanical and metabolic disruptions, membrane disruptions, large sections of inner hair cell loss, neural cell death, etc.
Do audibility objectives differ for those with severe to profound loss than those used for mild to moderate loss?
Yes
Reduced reliance on audibility
This population relies on alternative communication strategies which are supplemented by amplification
Amplification may be needed to support speech reading skills or for environmental sound awareness
May prefer a linear signal and prefer a signal processing of one brand
Do individual sound quality preferences vary?
Yes
Some individuals may not be able to extract information from a compressed signal, others need less compression to decode the incoming signal
Don’t rely on a targeted approach; begin with very low CR’s & listen to your patient instead
If they complain that speech is ‘muddled’, or indistinct modifications are needed, change to slow acting compression to maintain a longer non-compressed state (maintain a more linear aspect of the speech signal, reduce CR, audibility of the signal only above the LTASS may be preferred)
What is the recommended verification protocol for severe to profound losses?
Use a prescriptive formula designed for this population (NAL-RP)
Begin by establishing their upper-level limits (LDL) (reset MPO to LDL in fitting software to maximize available headroom)
Evaluate audibility at 65 dB SPL
It’s okay if signal audibility below LTASS may not be possible
Verifying a 55 dB signal isn’t necessary
Use objective assessments to evaluate patient’s ability to extract speech cues
Sentences in quiet; sentences in noise vs. noise; sentence with speech reading
