Lec 9: Prescriptions - Case Studies

Hearing Aid Prescriptions: Goals and Rationale

• Definition and Purpose: Hearing prescriptions are evidence-based tools used to determine the exact amount of gain needed for a hearing aid fitting based on audiometric characteristics.

• Audiometric Indicators: While prescriptions primarily rely on Pure Tone Average ($PTA$) thresholds, they can also incorporate loudness discomfort levels.

• Fitting Within Dynamic Range: Prescriptions must compress environmental sounds into the client’s reduced dynamic range. This is particularly crucial for sensorineural hearing loss, where the threshold for soft sounds is elevated, but the threshold for loud sounds often remains near normal.

  • Loudness Normalization: A goal to make soft sounds sound soft and loud sounds sound loud to the user.

  • Loudness Equalization: A distinct approach (often used by $NAL$) that aims to make all frequencies contribute equally to the perceived loudness.

• Speech Intelligibility: The overarching objective for most prescriptions is to maximize the client's ability to understand speech while maintaining listening comfort.

Historical Overview and the Evolution of Prescriptions

• Initial Approaches: Early fittings attempted to provide gain equal to the loss (e.g., if a client had a $30\,dB$ loss, they were given $30\,dB$ of gain).

  • The Limitation: This made loud sounds ($80\,dB$) uncomfortably loud ($110\,dB$) for the patient.

• The Half-Gain Rule: A following iteration where gain was set at half of the hearing loss (e.g., $15\,dB$ of gain for a $30\,dB$ loss).

• The Third-Gain Rule: A further variation placing more emphasis on the speech spectrum and loudness preferences.

• NAL-NL1 to NAL-NL2: The transition occurred because users found $NAL-NL1$ to be generally too loud. $NAL-NL2$ was designed to provide a slightly softer overall output.

Speech Spectrum and Cochlear Considerations

• Long Term Average Speech Spectrum (LTASS): This represents the pitch and loudness region where most speech falls for a speaker approximately $1\,m$ away at a normal volume. The prescription objective is to bring aided thresholds into this "speech banana."

• Cochlear Dead Regions: When thresholds reach or exceed $90\,dB$, there is a high probability of hair cell loss.

  • Off-Frequency Hearing: Over-amplifying dead regions can cause the traveling wave in the cochlea to spread and stimulate adjacent frequencies, causing significant sound distortion.

  • Clinical Testing: The Threshold Equalizing Noise ($TEN$) test is used to identify these regions and guide gain decisions.

• Acclimatization: Gain is rarely set to the full prescribed level immediately. A "dimmer switch" approach is used to gradually increase gain as the client adjusts to the sound.

Generic Prescription Philosophies (NAL vs. DSL)

• NAL (National Acoustics Laboratories): Includes $NL1$, $NL2$, and the recent $NL3$. These are non-linear prescriptions using compression.

  • Rationale: Loudness Equalization. By boosting high frequencies to a level of equal perceived loudness, speech intelligibility is improved.

  • SII Calculation: Uses the Modified Speech Intelligibility Index. It accounts for level distortion, where speech understanding actually decreases when sounds exceed $73\,dB$.

• DSL (Desired Sensation Level): Currently version $v5$. Originally developed for children, though adult versions exist.

  • Rationale: Loudness Normalization. It focuses on making soft sounds audible and loud sounds comfortable within the client’s specific levels.

  • Characteristics: DSL tends to prescribe higher gain in mid-frequencies and is generally more linear compared to $NAL-NL2$.

Speech Intelligibility Index (SII) and Clinical Application

• The SII Percentage: Visible in software like Affinity, this is a prediction of how much speech a person can hear (0% to 100%).

• Count-the-Dots Audiogram: A manual method where dots represent pieces of speech information across frequencies. The SII is the percentage of dots rendered audible by the aid.

• Matching to Target Limitations: Realistic constraints prevent a perfect $100\%$ match, including:

  • MPO and Feedback Managers: These may cut high-frequency gain.

  • Coupling: Open domes provide ventilation but let gain escape; if improper, volume increases in software do not reach the eardrum.

  • Channels: Fewer channels limit the precision of matching specific frequency peaks.

  • Patient Preference: Conductive and severe loss patients often subjectively prefer less gain than prescribed.

NAL-NL2 vs. NAL-NL3: Updates and Modern Research

• NAL-NL1 vs. NAL-NL2: $NL2$ introduced corrections for age, gender, and tonal vs. non-tonal languages. It is overall softer but provides slightly more high-frequency gain than $NL1$.

• Tonal vs. Non-Tonal Differences: Tonal languages have less information in the high frequencies, and prescriptions are adjusted accordingly.

• NAL-NL3 New Features:

  • New User Adjustments: Reduces "tinny" or artificial tones initially.

  • Specialized Adjustments: Targeted improvements for reverse sloping, mixed, and conductive losses.

  • Minimum Hearing Loss Module: Based on research into Low Gain Hearing Aids for patients with functional hearing difficulties despite normal $PTA$ (e.g., Hidden Hearing Loss, Extended High-Frequency Loss, or Auditory Processing Disorders like $Listen-S$).

Atypical Case Study: 72-Year-Old Male with Sudden Change

• Initial Status: Mild hearing loss for $10$ years; no desire for aids.

• The Incident: Left ear infection followed by ENT-placed grommets. Symptoms (oral fullness) persisted after grommet placement.

• Clinical Presentation: Asymmetric sensorineural loss ($ACM$) post-grommet, with localized conductive components at low frequencies (e.g., $20\,dB$ at $250\,Hz$).

• Medical Red Flags: Sudden onset, asymmetric thresholds, and persistent fullness. Differential diagnoses include Acoustic Neuroma (retrocochlear), Meniere’s disease, or Mastoiditis.

• Pathology Resolution: An MRI confirmed opacity in the middle ear and mastoid cells (Mastoiditis). A subsequent fungal infection was also treated.

The Seven-Trial Journey: Evaluating Brands and Prescriptions

• Trial 1 (Oticon RIC): Open domes, matched to subjective comfort. Issue: Own voice too loud and whistling (feedback) in left ear.

• Trial 2 (Phonak): Attempted a power dome on the left for retention. Issue: Extreme feedback when hugging friends and poor sound quality in noise.

• Trial 3 (Signia Pure Charge&Go 7 IX): Utilized Own Voice Processing ($OVP$). Requires directional microphones. Issue: Felt blocked; hearing dropped due to medical complication (conductive).

• Trial 4 (Unitron Moxi v9 R): Used $NAL-NL2$. $REIG$ (Insertion Gain) was impossible due to discharge and grommets.

• Trial 5 (Phonak Audeo Lumity 90): Used Adaptive Phonak Digital (proprietary). More comfortable but subjective balance was poor.

• Trial 6 (DSL v5): Improved own voice clarity but performance in background noise was still underwhelming.

• Trial 7 (GN Nexia 9): $DSL$ at $80\%$ gain. Resulted in "tinny" sound quality; client rejected these aids.

• Final Outcome: The client eventually returned to the Phonak $L90$ set to $NAL-NL2$.

Questions & Discussion

• Question: Can clients with patent grommets fly or swim?

• Answer: Flying is fine because grommets allow the middle ear to equalize pressure easily. Swimming is a concern; clients should use earplugs to avoid water entry, especially dirty water.

• Question: Why did the user hate $NL2$ after being used to $NL1$?

• Answer: Acclimatization is powerful. Users used to the higher gain and greater volume of $NL1$ often find $NL2$ sounds "too soft" or "muffled."

• Question: For cognitive impairment, are rechargeables or batteries better?

• Answer: Either could be justified. Rechargeables favor a set daily routine, whereas batteries may be easier if the user forgets to charge the device at night.

Hearing Aid Prescriptions – Full Detailed Lecture Notes

Objectives

• Compare and contrast manufacturer prescriptions from ‘generic’ prescriptions

• Explain the benefits and limitations of manufacturer prescriptions, including when it can be used and how it can be verified

• Step through an atypical case where alternative prescriptions may need to be considered.

• Understand how to apply features from one prescription to another.

• Understand some of the gain differences prescribed for various rationale

Goals of Hearing Aid Prescriptions

Apply appropriate gain and output based on audiometric characteristics

Optimise audibility

With hearing loss:

• Dynamic range becomes reduced

Especially with sensorineural hearing loss:

• Soft sounds become difficult to hear

• Loud sounds may still be perceived as loud

Therefore:

• Hearing aid gain must fit sounds within the reduced dynamic range

The prescription is designed so:

• Clients can hear the sounds they need to hear

Loudness Normalisation

Purpose:

• Make loudness sound normal to the listener

This means:

• Soft sounds should still sound soft

• Loud sounds should still sound loud

Loudness Equalisation

Discussed later in relation to NAL prescriptions.

Maximise Speech Intelligibility

A major goal of most prescriptions.

Aim:

• Improve speech understanding

• Maximise speech intelligibility outcomes

Listening Comfort

Prescriptions should ensure:

• Sounds are comfortable

• Hearing aids are tolerable for the user

History of Hearing Aid Prescriptions

Earliest Approach – Full Gain

Initial idea:

• If a person had a 30 dB hearing loss

• Give 30 dB of gain

Problem:

• Loud sounds became excessively loud

Example:

• 80 dB sound + 30 dB gain = 110 dB

• Extremely loud and uncomfortable

Conclusion:

• Cannot simply add the amount of hearing loss as gain

Half-Gain Rule

Next approach:

• Provide half the hearing loss as gain

Example:

• 30 dB hearing loss → 15 dB gain

Result:

• Better than full gain

• But still not carefully individualised

Third-Gain Rules

Many prescriptions became:

• Variations of third-gain rules

• With more emphasis on speech

Loudness Preferences and Prescription Adjustments

Important consideration:

• Patient loudness preferences

Example:

• NAL-NL1 was perceived by many as too loud

• NAL-NL2 was developed to sound overall softer

Long-Term Average Speech Spectrum (LTASS)

The shaded region on the slide represented:

• Long-term average speech spectrum

Assumptions:

• Speaker standing about 1 metre away

• Speaking at normal conversational volume

Most speech falls within:

• A particular pitch and loudness region

Goal of hearing aid fitting:

• Place aided thresholds / aided response within this speech region

Cochlear Dead Regions

Important consideration during fitting.

Example discussed:

• Very poor thresholds above 3 kHz

• Thresholds 90 dB and above

Implications:

• High likelihood of cochlear dead regions

• Hair cells may be absent/non-functioning

Consequences of amplifying dead regions:

• Distortion of sound

• Limited benefit from amplification

Off-Frequency Listening

If excessive gain is provided:

• Especially at high frequencies

• Travelling wave may spread

• Adjacent hair cells may be stimulated

Result:

• Off-frequency listening

• Distorted perception

Therefore:

• Little benefit in providing large amounts of gain in dead regions

Testing for Cochlear Dead Regions

The lecture referenced:

• A test that could help determine cochlear dead regions

This can:

• Guide fitting decisions

Acclimatisation

Clinicians rarely:

• Turn hearing aids immediately to full prescribed gain

Reason:

• Patients often cannot tolerate full gain initially

Approach:

• Start at reduced gain

• Gradually increase over time

Analogy:

• Like a dimmer switch

Outcome:

• Patients gradually adjust to louder gain levels

Generic Prescriptions Covered

DSL

Versions mentioned:

• DSL i/o

• DSL v5

NAL Prescriptions

Mentioned:

• NAL-NL1

• NAL-NL2

• NAL-NL3

Main focus:

• NAL-NL1

• NAL-NL2

Both are:

• Non-linear prescriptions

• Use compression

NAL-NL1

Main Goal

• Speech intelligibility

Underlying Rationale

• Loudness equalisation

DSL uses:

• Loudness normalisation

Loudness Equalisation

Goal:

• Keep loudness equal across frequencies

Example:

• 2 kHz should sound equally loud as 4 kHz

Difference from normal hearing:

• Normally lower frequencies naturally sound louder

NAL equalisation therefore:

• Distorts this natural balance somewhat

Purpose:

• Provide more high-frequency audibility

• Improve speech intelligibility

Basis of NAL-NL1

Based on:

• Modified Speech Intelligibility Index (SII)

• Loudness perception model

Speech Intelligibility Index (SII)

In Affinity:

• Appears beside the trace list and tick boxes

• Displayed as a percentage

What it represents:

• Prediction of how much speech the person can hear

Count-the-Dots Audiogram

SII can also be estimated manually using:

• Count-the-dots audiogram

Features:

• More dots in high frequencies

• Fewer dots in low frequencies

Reason:

• High frequencies contain more speech information

Procedure:

• Overlay audiogram

• Count audible vs inaudible dots

Then:

• Calculate percentage

• Gives SII

SII During REMs

Better match to target:

• Higher SII

Poor match to target:

• Lower SII

100% SII is very rare because:

• All responses would need to exceed target completely

• Most patients prefer slightly less gain

Reasons Why Perfect Match to Target May Not Be Possible

1. MPO and Feedback Management

• High-frequency gain may be limited

• Feedback managers may reduce gain

2. Acoustic Coupling Limitations

Example:

• Open dome used inappropriately

What happens:

• Gain increased in software

• REM does not change significantly

Reason:

• Gain not effectively reaching eardrum

Therefore:

• Coupling selection is important

3. Limited Number of Channels

Problem:

• Adjusting one frequency region may affect another

• Cannot perfectly match target

4. Patient Preferences

Some patients:

• Find prescribed gain too loud

• Prefer reduced gain

Examples:

• New users

• Patients with severe hearing loss

• Some patients with conductive hearing loss

Interesting point:

• Conductive losses theoretically should not involve recruitment

• Yet many still prefer less gain than prescribed

Level Distortion Factors

NAL found:

• Speech levels above 73 dB can become distorted

Therefore:

• Included in modified SII calculations

Higher speech levels:

• May reduce speech understanding

NAL-NL2

Released:

• Approximately 10–12 years ago

Still based on:

• Loudness equalisation

Additional Factors Included in NAL-NL2

Accounts for:

• Age

• Gender

• Acclimatisation

• Tonal vs non-tonal languages

Differences from NAL-NL1

Softer Overall

Reason:

• Feedback from users that NL1 sounded too loud

More High-Frequency Gain

Compared to NL1:

• More high-frequency gain

• Then drops off in very high frequencies

Tonal vs Non-Tonal Languages

Tonal language prescriptions:

• Slightly more gain

• Less emphasis on high frequencies

Reason:

• Tonal languages contain less high-frequency information

Switching Long-Term Users from NL1 to NL2

Possible complaints:

• Too quiet

• Tinny

Clinical observation:

• Patients often do not adapt well if changed from a long-used prescription

NAL-NL3

Same overall purpose:

• Maximise speech intelligibility

• Maintain comfort for loud sounds

Features of NAL-NL3

Reduced Excessive High-Frequency Gain

Reason:

• New users often complain hearing aids sound:

  • Tinny

  • Artificial

Improved Prescription for Reverse-Sloping and Mixed Losses

Especially:

• Less gain for conductive losses

Reason:

• Conductive loss patients often prefer less gain

Limits High Compression Ratios

Avoid:

• Too much gain for soft sounds

• Too little gain for loud sounds

Minimum Hearing Loss Module

Older approach:

• Reassure patients with normal hearing that hearing is fine

Problem:

• Patients may still report listening difficulties

Current research:

• Investigating low-gain hearing aids

Causes of Listening Difficulties Despite Normal Audiograms

1. Reduced Outer Hair Cell Function

Pure tone audiograms mainly test:

• Inner hair cell detection thresholds

They do not strongly assess:

• Outer hair cell amplification function

2. Hearing Loss Outside Standard Test Frequencies

Standard testing:

• 250 Hz to 8 kHz

Extended high-frequency loss:

• May contribute to listening difficulties

3. Auditory Processing Issues

Example:

• Poor LiSN-S performance

Meaning:

• Functional hearing ability may differ from PTA results

Low-Gain Hearing Aids

The lecturer discussed:

• Limited evidence-based protocols currently

Clinical experience described as:

• Somewhat vague

Suggested approach previously received:

• Use REMs

• Aim for approximately 5 dB gain

• Do not worry excessively about exact target

Lecturer commented:

• This felt non-evidence-based

• More evidence-based prescription systems would be useful

DSL

Originally developed for:

• Children

Can also be set for:

• Adults

DSL Philosophy

Uses:

• Loudness normalisation

Goals:

• Very soft sounds audible

• Medium sounds comfortable

• Very loud sounds below discomfort levels

Essentially:

• Compress everything into the dynamic range

Differences Between DSL and NAL-NL2

DSL tends to:

• Have more medium gain

• Sound louder overall

• Be more linear

NAL-NL2:

• More compression

Detailed Case Study

Initial Presentation

Patient:

• 72-year-old male

History:

• Mild hearing loss for approximately 10 years

• Generally healthy

Initially:

• Not keen on hearing aids

• Felt difficulties were manageable

Family influence:

• Another family member had more severe hearing loss and required hearing aids

• Patient preferred to focus on helping family adapt first

Follow-Up Two Years Later

Patient developed:

• Ear infection in left ear

• Felt hearing worsened in left ear

Initial symptoms:

• Sore ears

• Hearing change

Management by ENT:

• Grommets inserted

Timeline:

• Approximately 6 weeks before overseas trip

• Saw ENT

• Received grommets

• Travelled overseas

• Returned for audiology follow-up

Audiogram available:

• Only post-grommet audiogram

Symptoms persisted after return.

Clinical Red Flags

1. Sensorineural Asymmetry

2. Significant Audiometric Change

Compared to previous audiogram:

• Thresholds had worsened substantially

3. Possible Sudden Sensorineural Hearing Loss

Patient history suggested:

• Sudden change associated with "ear infection"

Concern:

• Possible missed sudden sensorineural hearing loss

Concerns Regarding Grommets

Discussion points:

• Possible questionable management

• Persistent symptoms despite grommets

If grommets are patent:

• Patient should not feel blocked

Persistent aural fullness therefore raised concern.

Differential Diagnoses Discussed

1. Retrocochlear Pathology

2. Nasopharyngeal Issues

3. Ménière’s Disease

Why less likely:

• Typically low-frequency fluctuating loss

• No fluctuating symptoms reported

• No classic vestibular symptoms

However:

• Clinicians encouraged to think broadly

• Avoid prematurely assuming acoustic neuroma

Flying with Grommets

Question:

• Can patient fly comfortably?

Answer:

• Yes

Reason:

• Grommets allow pressure equalisation

• Prevent problematic middle-ear pressure changes

Swimming with Grommets

Recommendation:

• Use earplugs

Especially important in:

• Dirty water

Additional History Needed

1. Timing of Hearing Change

• Sudden vs gradual

2. Tinnitus

3. Communication Difficulties

• Impact on daily life

4. Vestibular Symptoms

• Vertigo

• Imbalance

Patient reportedly had:

• No vertigo or balance symptoms

Updated Clinical Thinking

Patient now:

• Felt hearing was becoming socially problematic

Management plan:

Amplification

Discuss hearing aids.

Referral

Referral:

• GP → Different ENT

Reason:

• Further investigation

• MRI requested

ABR Discussion

ABR may help:

• Assess nerve conduction

• Decide need for MRI

However:

• Less useful if MRI definitely proceeding

Clearance for Hearing Aids

Not required for:

• Grommets

• Asymmetry alone

Need caution and referrals:

• But no ENT sign-off required

Conductive components only require clearance if:

• Active infection

• Discharge

• Pain

ENT and MRI Findings

ENT findings:

• Otitis media with effusion

MRI findings:

• No retrocochlear pathology

• Opacity in middle ear and mastoid cells

Interpretation:

• Fluid/mastoid involvement

This explained:

• Aural fullness

Initial Hearing Aid Considerations

Goal:

• Trial hearing aids while condition managed medically

Coupling Considerations

Open fitting preferred.

Reason:

• Avoid worsening conductive component

Styles considered:

• BTE

• RIC

BTE preferred because:

• RIC receiver could be damaged by discharge

Open Dome Considerations

Advantages:

• Better ventilation

Disadvantages:

• Increased risk of feedback

Especially concerning with this audiogram.

BAHA Discussion

Not considered ideal initially because:

• Hearing loss mainly sensorineural

• Audiometric thresholds near eligibility limits

Would only consider if:

• Conventional hearing aids unsuccessful

First Trial – Oticon RIC

Patient chose:

• Oticon RIC

• Open domes bilaterally

Prescription:

• NAL-NL2

Observation:

• Software gain much lower than prescribed target

Reason:

• Patient felt prescribed gain too loud

• Gain reduced for comfort

Three-Week Follow-Up

Positive:

• Physical comfort acceptable

Problems:

• Poor hearing in noise

• Own voice too loud

• Partner struggled hearing patient during dinner conversations

• Left hearing aid whistling/feedback

Audiogram:

• No major change

Clinical Interpretation

Important findings:

• Open dome not working well

• Own voice major issue

• No physical complications from dome use

Possible considerations:

• Reduce gain further

• Check acclimatisation

• Assess data logging

Data Logging Importance

If low usage:

• Poor acclimatisation may contribute to own voice complaints

Counselling point:

• Consistent use needed for adaptation

Major Strategy Shift

Decision:

• Try completely different hearing aid/manufacturer

Reason:

• Large changes may produce faster improvement than small adjustments

Manufacturer prescriptions often:

• More comfortable

• Less high-frequency gain

Second Trial – Phonak

Results after trial:

Positives

• Physical comfort acceptable in right ear

Problems

• Left power dome would not stay in

• Significant feedback

• Own voice still too loud

• Partner still unable to hear patient properly

• Patient anxious about ear condition

Data Logging

Usage:

• 9.5 hours/day

Interpretation:

• Good usage

Coupling Considerations

Options discussed:

• Mould

• Retention line

• Different dome size

Clinical Thinking

Hearing loss now appeared:

• Stable

Decision:

• Continue hearing aid exploration

Third Trial – Signia

Device:

• Pure Charge&Go IX 7

• Rechargeable RIC

• High-end technology level

Receivers:

• Standard receiver right ear

• Medium receiver left ear

Why Signia?

Key feature:

• Own Voice Processing (OVP)

Procedure:

• Patient sits away from nearby objects

• Counts aloud continuously

• Software analyses voice

• Reduces own voice perception automatically

Advantages:

• Particularly useful for patients struggling with own voice

Limitation:

• Requires directional microphones

• Cannot be used in IIC devices

Prescription Used

• Signia manufacturer prescription

• New user setting

Verifying Manufacturer Prescriptions

Cannot directly verify in Affinity because:

• Manufacturer proprietary prescriptions unavailable there

Alternative:

• Run REMs through manufacturer software

Procedure:

• Software guides clinician step-by-step

• Some systems automatically adjust toward target

Are REMs Essential Here?

Discussion:

• Perhaps less critical in this specific case

Reason:

• Previous fittings already reduced far below target

• Comfort more important than strict target matching during trials

Two-Week Follow-Up After Signia

Positives:

• Physical fit acceptable

• Less feedback

Problems:

• Feedback still present

• Own voice still problematic

• Unsure whether left hearing aid working

• Background noise still difficult

• Ears felt more blocked

Major Concern

Possibility:

• Hearing worsening rather than hearing aid malfunction

Clinical response:

• Repeat audiogram

Audiogram Findings

Findings:

• New conductive component

• Air thresholds worsened

Management:

• Pause hearing aid process

• Refer back to ENT

Return After Medical Treatment

Conductive component improved.

Review of previous trials:

• Own voice still problematic

• Comfort/acoustics important

• No major success yet

Patient felt:

• Initial Oticon perhaps best overall

Fourth Trial – Unitron

Device:

• Moxi V9-R

• Rechargeable RIC

Coupling:

• Open dome right ear

• Vented dome left ear

Prescription:

• NAL-NL2

Fitting Range Considerations

Important for HSP:

• Hearing aid must fit hearing loss

• Should allow approximately 10 dB headroom for deterioration

Observation:

• Left side near fitting limit

• Could improve with more closed coupling

REM Issues with Grommets and Discharge

Problems:

• Probe tubes can block with discharge

Grommets/perforations alter acoustics:

• Abnormal REUG traces

• Possible shifted resonances

• Double peaks

Research suggests:

• Patients prefer gain based on normal REUG assumptions

Alternative verification:

• Coupler measures

Follow-Up After Unitron

Findings:

• Own voice still problematic

• Partner still struggled hearing patient in noise

• Comfort better with vented dome

• Patient thought Phonak still best overall

Return to Phonak

Device:

• Phonak Audéo Lumity L90

• Top-level technology

Actions:

• Transferred settings from previous Paradise fitting

• Reduced acclimatisation to 90%

• Changed fitting formula to Adaptive Phonak Digital

Differences Between Phonak Prescription and NAL-NL2

Less High-Frequency Gain

Manufacturer prescriptions often:

• Sound more comfortable

• Better for new users

Less Compression

More linear fitting.

Gain curves:

• Closer together compared to NAL

Patient Response

Problems:

• Own voice still too loud

• Right ear too soft

• Left ear too loud

• Poor subjective balance

Switch to DSL

Reasoning:

• Loudness normalisation may preserve more natural sound quality

• Lower compression ratios preserve speech contrasts

Adjustments:

• Right ear kept at prescribed gain

• Left ear reduced overall for subjective balance

Response to DSL

Improvements:

• Subjective balance improved

• Own voice much better

• Sound clearer

• Overall comfortable

Still present:

• Slight sharpness

• Ongoing grommet discharge

Patient took aids for trial.

Follow-Up Two Weeks Later

Positive outcomes:

• Partner could hear patient better at dinner

• Own voice significantly improved

• Hearing others reasonably well

• Comfort good

Remaining issue:

• Performance somewhat underwhelming

Clinician response:

• Discuss realistic expectations

• Acknowledge nearing practical limits

Fifth Trial – GN ReSound

Device:

• GN Nexia 9

Coupling:

• Closed domes bilaterally

Prescription:

• DSL

Observations

More linear response.

High-frequency gain reduced because:

• Feedback management limitations

• Patient sensitivity to loudness

Feedback region shown in software.

Outcome of GN Trial

Patient disliked:

• Tinny sound quality

• Did not wear hearing aids

Requested return to:

• Phonak L90s

Final Outcome

Patient eventually:

• Purchased Phonak L90s elsewhere

• Using NAL-NL2

• Reported good satisfaction

Clinical Reflections from the Case

Importance of Support

Even though many trials occurred:

• Clinicians supported patient through adjustment process

• Helped patient adapt emotionally and practically

Value of Exploring Multiple Options

Patient learned:

• Many hearing aid options exist

• Multiple brands/settings available

This helped:

• Reduce anxiety

• Improve confidence in rehabilitation process

Prescriptions May Change Over Time

Example:

• DSL initially worked well

• Later patient disliked DSL

Therefore:

• Preferences can shift with acclimatisation

Importance of Large Changes

When fittings fail repeatedly:

• Large changes may work better than small adjustments

Examples:

• Different brands

• Different prescriptions

• Different coupling

Beyond REMs

Other important measures:

• Data logging

• Satisfaction reports

• Questionnaires

Examples:

• IOI-HA

• COSI

Medical Outcome

Eventually:

• Fungal middle-ear infection resolved

• Grommets removed/fell out

• Tympanic membranes healed

• Hearing returned to sensorineural loss only

Additional Clinical Notes

Using Different Prescriptions in Clinic

Example described:

• Oticon hearing aids programmed with:

  • One program using NAL-NL2

  • Another using NAL-NL1

Purpose:

• Allow patient comparison

Outcome:

• Patient preferred NL2

Important Clinical Principle

Patients accustomed to NAL-NL1:

• May find NL2 too soft

Real clinical example:

• Patient had been switched from NL1 to NL2

• Never satisfied afterward

• Immediate improvement after switching back to NL1

Final Key Message

The biggest factor to keep in mind:

Individual Preferences

Different patients:

• Prefer different prescriptions

• Prefer different sound qualities

• Adapt differently over time

Clinicians should:

• Understand rationale behind prescriptions

• Be flexible

• Be prepared to switch prescriptions when needed

• Combine objective and subjective outcomes in decision making