Special Cases and Hearing Aid Programming Alternatives

Question 1

Does binaural summation and squelch require fusion of the signals delivered to the ear?

Answer 1

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

Question 2

Do patients with asymmetric losses benefit from bilateral amplification?

Answer 2

Yes
Even though they may not fully enjoy the binaural advantage

Question 3

What defines an asymmetric loss?

Answer 3

3 adjacent frequencies of > 20 dB
1 frequency > 25 dB
Asymmetric speech intelligibility
Asymmetric SNR loss (20% difference)
Asymmetric LDL

Question 4

What are some things to consider when fitting an asymmetrical loss with bilateral amplification?

Answer 4

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

Question 5

When should you only aid the better ear (CROS or BiCROS)?

Answer 5

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)

Question 6

When would you aid the poorer ear only to balance signal audibility and supply some binaural benefit?

Answer 6

The better ear has near normal thresholds in critical speech ranges

Question 7

When would you fit both ears (asymmetric loss) and let the patient experience and determine the value of binaural amplification?

Answer 7

If both ears may assist speech intelligibility to some degree

Question 8

What are some fitting strategies for bilateral devices?

Answer 8

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

Question 9

How do you determine the best prescriptive formula for the patient?

Answer 9

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)

Question 10

What questions should the audiologist answer before fitting an asymmetrical hearing loss?

Answer 10

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?

Question 11

Should you discuss realistic expectations of benefits and limitations (of binaural amp with an asymmetric loss) with the patient?

Answer 11

Yes
Conduct unaided/aided unilateral/ aided assessments and share comparative test data

Question 12

What are some alternative options for patients with asymmetrical losses?

Answer 12

CROS
BiCROS
AmpCROS
Bone-anchored implantables
CI
Remote mic

Question 13

What is a CROS?

Answer 13

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

Question 14

What is a BiCROS?

Answer 14

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

Question 15

What is ampCROS?

Answer 15

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

Question 16

How is CROS verification done?

Answer 16

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)

Question 17

How do you set up the audioscan for CROS verification?

Answer 17

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

Question 18

How should you measure an REUR on a CROS?

Answer 18

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

Question 19

How do you measure the head shadow with a CROS?

Answer 19

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

Question 20

How do you measure CROS effect?

Answer 20

Device set up for CROS
Patient still 45 degrees with the better ear toward the speaker

Question 21

How do you verify BiCROS fittings?

Answer 21

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”

Question 22

What is a transcranial CROS?

Answer 22

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)

Question 23

What losses were DSL and NAL designed to fit?

Answer 23

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)

Question 24

What is the verification for NIHL focused on?

Answer 24

Audibility of residual hearing within healthier regions of the cochlea

Question 25

What are the 3 types of NIHL?

Answer 25

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

Question 26

What are some challenges associated with type 2 and 3 NIHL?

Answer 26

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

Question 27

What are the old theories for cochlear dead regions?

Answer 27

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

Question 28

What does the current research about dead regions suggest?

Answer 28

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

Question 29

Are special fitting strategies needed for patients with the presence of 1 to 2 dead regions?

Answer 29

No

Question 30

Are special fitting strategies needed for patients with extensive dead regions?

Answer 30

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)

Question 31

How do you choose a receiver for a patient with a severe sloping loss?

Answer 31

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

Question 32

What are some fitting strategies for type 3 NIHL?

Answer 32

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%)

Question 33

What are some additional fitting considerations for those with type 2 or 3 NIHL?

Answer 33

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

Question 34

Study up to here for the midterm

Question 35

When should frequency lowering be enabled for the adult population?

Answer 35

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

Question 36

Which manufacturers use frequency compression?

Answer 36

Phonak, Unitron, Signia

Question 37

What manufacturer uses frequency transposition?

Answer 37

Widex

Question 38

Which manufacturers use spectral warping?

Answer 38

Starkey, Oticon, Bernafon

Question 39

What losses is FL beneficial to?

Answer 39

Steeply sloping loss
Severe to profound loss

Question 40

What is our goal behind FL?

Answer 40

Fine-tune to the weakest possible setting for improved audibility

Question 41

What can result from FL?

Answer 41

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

Question 42

What is the maximum audible output frequency (MAOF)?

Answer 42

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

Question 43

How do you assess FL candidacy?

Answer 43

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)

Question 44

Is verification of spectral warping different?

Answer 44

Yes
It copies the original HF signal and transposes it to the lower frequencies
Observe both humps on graph

Question 45

Is there an increased prevalence of LF IHC loss with reverse slope loss?

Answer 45

Yes

Question 46

Do dead regions exist with reverse slope SNHL?

Answer 46

Yes

Question 47

What do the fitting strategies for reverse slop losses focus on?

Answer 47

Audibility within residual hearing regions (healthier regions of the cochlea)

Question 48

What leads to unsuccessful fittings for reverse slope losses?

Answer 48

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)

Question 49

How do you fit reverse slope losses?

Answer 49

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

Question 50

Is additional gain needed to overcome the attenuation caused by mechanical loss?

Answer 50

Yes
Air/bone gaps attenuate the signal’s amplitude before it arrives to the cochlea

Question 51

Do you need compression when fitting a loss with ABGs with normal BC thresholds?

Answer 51

No
Compression is not needed because the dynamic range is normal
Use of 1:1 linear signal processing (or very low CR) is fine

Question 52

Do you need compression with a mixed loss?

Answer 52

Yes
Compression is needed in addition extra gain due to the reduced dynamic range

Question 53

How do you calculate additional gain for a loss with an ABG?

Answer 53

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

Question 54

Do NAL formulas automatically calculate the ABG?

Answer 54

Yes
Provides this calculation when the BC thresholds are entered into the verification unit
DSL 5.0 does not compensate for additional gain needs

Question 55

Do all of the fitting software algorithms include the adjustment for ABG?

Answer 55

Maybe yes, but maybe no!
Each brand you use must be evaluated to identify potential limitations

Question 56

What threshold loss will result from a small perf (1-2 mm)?

Answer 56

Minimal hearing loss

Question 57

What threshold loss will result from a larger perf?

Answer 57

25-35 dB CHL

Question 58

What threshold loss will result from a total TM perf?

Answer 58

About 40 dB CHL

Question 59

What threshold loss will result from a posterior-superior with ossicular erosion?

Answer 59

Could be a loss as great as 60 dB

Question 60

What are some options when perfs are present?

Answer 60

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)

Question 61

Can you think of the severe to profound SNHL as a whole?

Answer 61

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.

Question 62

Do audibility objectives differ for those with severe to profound loss than those used for mild to moderate loss?

Answer 62

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

Question 63

Do individual sound quality preferences vary?

Answer 63

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)

Question 64

What is the recommended verification protocol for severe to profound losses?

Answer 64

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