Non-Organic Hearing Loss, Pseudohypacusis & Stenger Testing

Non-Organic Hearing Loss, Pseudohypacusis & Stenger Testing

Identifying and managing non-organic hearing loss is a vital clinical competency in audiology. Non-organic hearing loss occurs frequently in medical-legal compensation claims, veterans' disability evaluations, industrial injury litigation, pediatric school-avoidance behaviors, and psychiatric distress. Audiologists must identify false or exaggerated thresholds, estimate true hearing sensitivity, and maintain an objective, non-adversarial clinical relationship.

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Diagnostic Terminology & Etiological Spectrum

Precise clinical terminology is legally and diagnostically essential in audiologic medical records.

Medical-Legal Charting Caveat: Audiologists should never document "malingering" in the medical record. Malingering denotes legal and criminal intent, which cannot be proven by behavioral test results alone. Always use objective terms: "Results demonstrate non-organic hearing loss / pseudohypacusis" or "Behavioral thresholds are inconsistent with objective electrophysiologic measures."

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Clinical Behavioral Indicators & "Red Flags"

Experienced clinicians recognize behavioral patterns that signal pseudohypacusis prior to and during audiometric testing:

Inconsistent Intake vs. Formal Test Behaviors

• Casual Communication vs. Booth Straining: The patient converses effortlessly with the clinician in the waiting room at normal speech levels ($50-60\,\text{dB SPL}$) without visual cues, but in the sound suite demonstrates exaggerated straining, cupping their ears, or claiming inability to hear speech presented at $70\,\text{dB HL}$.
• Exaggerated Reliance on Lipreading: The patient stares intensely at the clinician's mouth and covers their own ears, yet immediately ceases this behavior when the clinician speaks softly while writing or facing away.

Pure-Tone Audiometric Behaviors

• Unusual Response Latencies: Excessively slow, hesitant, or delayed responses. The patient waits several seconds after tone termination before pressing the response button, attempting to evaluate tone loudness.
• False-Positive Absence: A total absence of false-positive responses. Patients with organic hearing loss near threshold frequently guess or demonstrate occasional false alarms; patients with pseudohypacusis rarely respond unless they are certain a sound is above their chosen criteria.
• Ascending vs. Descending Discrepancy ($> 10\,\text{dB}$): In organic hearing loss, ascending and descending thresholds agree within $\pm 5\,\text{dB}$. In pseudohypacusis, descending thresholds are routinely $10-20\,\text{dB}$ better (lower) than ascending thresholds because the patient loses their mental "loudness anchor" as sound intensity decreases.
• The Pediatric "Yes-No" Test: In children feigning hearing loss, instruct: "Say 'Yes' when you hear the beep, and say 'No' when you don't hear it." A child with pseudohypacusis will consistently reply "No" immediately following sub-threshold tone presentations, proving auditory detection.

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The Classic PTA-SRT Discrepancy

The Audiological Cross-Check Rule

In an organic hearing loss, the 3-frequency pure-tone average (PTA across 500, 1000, and 2000 Hz) and the Speech Recognition Threshold (SRT) must agree within $\pm 6\,\text{dB}$ (maximum allowable variance $\pm 10-12\,\text{dB}$ in sharply sloping losses when using the 2-frequency Fletcher average):

$|\text{PTA} - \text{SRT}| \le 6-10\,\text{dB}$

The Pseudohypacusic Discrepancy Pattern

In non-organic hearing loss, a dramatic discrepancy is observed where the SRT is significantly better (lower in dB HL) than the PTA:

$\text{PTA} - \text{SRT} > 12\,\text{dB} \quad (\text{frequently } 20-50\,\text{dB better})$

Psychoacoustic Mechanism: Why is the SRT consistently better than the PTA in pseudohypacusis?

1. Spondee Loudness Growth & Redundancy: Spondaic words (bisyllabic words with equal stress: baseball, hotdog, ice cream, cowboy) possess broad spectral energy and high semantic redundancy. The psychometric intelligibility function for spondees is exceptionally steep, rising from $0\%$ to $100\%$ over a narrow dynamic range of only $8-10\,\text{dB}$.
2. Cognitive Loudness Estimation: It is cognitively difficult for an untrained listener to judge loudness sensation for complex speech. At $10-15\,\text{dB}$ above true threshold, spondees sound remarkably clear and loud. The patient perceives the word clearly and involuntarily repeats it, assuming it is being presented at a high conversational level. Conversely, single pure tones allow the patient to consciously suppress responses until a specific subjective loudness criterion is met.

Diagnostic Warning: An SRT that is significantly poorer (worse) than the PTA ($|\text{SRT} - \text{PTA}| > 10\,\text{dB}$ with poor speech) does not indicate pseudohypacusis. This pattern suggests retrocochlear pathology, Auditory Neuropathy Spectrum Disorder (ANSD), central auditory processing disorder, cognitive decline, or non-native language fluency.

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Absence of Expected Cross-Hearing ("Shadow Curves")

Physical Laws of Cranial Transmission

In patients reporting an apparent severe or profound unilateral hearing loss, the physical laws of interaural attenuation dictate that cross-hearing must occur during unmasked testing:

• Supra-aural headphones: $\text{IA} = 40\,\text{dB}$.
• Insert earphones: $\text{IA}$ about $50-70\,\text{dB}$ (frequency dependent).
• Bone conduction vibrator: $\text{IA} = 0\,\text{dB}$.

The Shadow Curve Diagnostic Marker

If a patient reports a normal left ear ($0-10\,\text{dB HL}$) and claims a total, profound right-ear hearing loss (no responses at $90-110\,\text{dB HL}$ unmasked):

• When a tone is presented to the right ear at $100\,\text{dB HL}$ via supra-aural headphones, the sound cross-attenuates by $40\,\text{dB}$ and arrives at the left cochlea at $60\,\text{dB HL}$.
• Because the left cochlea has a $0-10\,\text{dB HL}$ threshold, the left cochlea perceives that sound with a roaring sensation level of $+50\,\text{dB SL}$!
• A patient with true organic unilateral deafness cannot prevent their normal ear from hearing that crossed tone; they will reliably respond, producing an unmasked shadow curve at $40-50\,\text{dB HL}$.
• If the patient produces unmasked right-ear thresholds of $100\,\text{dB HL}$ or "no response" without a shadow curve, this violates basic cranial acoustic physics. The absence of a shadow curve in unilateral profound hearing loss is definitive proof of non-organic hearing loss.

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The Stenger Phenomenon & Clinical Stenger Protocol

The Psychoacoustic Stenger Phenomenon

Discovered by German otolaryngologist Paul Stenger in 1900, the Stenger phenomenon states:

When two identical acoustic signals (identical frequency and phase) are presented simultaneously to both ears, the brain perceives the sound exclusively in the ear where the sound has a higher sensation level (SL). The listener is completely unaware of the sound presented to the contralateral ear.

Patient Candidacy for the Stenger Test

The Stenger test is indicated whenever an asymmetrical hearing loss is present, defined as an interaural threshold difference of $20\,\text{dB}$ or greater at any test frequency ($250-8000\,\text{Hz}$) or for speech stimuli (Speech Stenger).

Step-by-Step Stenger Test Protocol

Consider a patient with the following admitted thresholds at $1000\,\text{Hz}$:

• Better Ear (Right): Admitted Threshold $= 10\,\text{dB HL}$
• Poorer Ear (Left): Admitted Threshold $= 70\,\text{dB HL}$ (Interaural difference $= 60\,\text{dB} \ge 20\,\text{dB}$)

1. Step 1 (Better Ear Verification): Present tone to the better ear alone at $+10\,\text{dB SL}$ ($10 + 10 = 20\,\text{dB HL}$). Patient responds reliably.
2. Step 2 (Poorer Ear Verification): Present tone to the poorer ear alone at $10\,\text{dB}$ below admitted threshold ($70 - 10 = 60\,\text{dB HL}$). Patient does not respond (consistent with their admitted $70\,\text{dB}$ threshold).
3. Step 3 (Simultaneous Stenger Presentation): Present both tones simultaneously using an interlocked dual-channel audiometer:
   • Better Ear (Right): $20\,\text{dB HL}$ ($+10\,\text{dB SL}$)
   • Poorer Ear (Left): $60\,\text{dB HL}$ ($-10\,\text{dB}$ below admitted threshold)

Interpreting Stenger Test Results

Minimum Stenger Level (MSL) Procedure

The Minimum Stenger Level (MSL) procedure allows the audiologist to accurately estimate true auditory threshold in the poorer ear without the patient's active cooperation:

1. Keep the tone in the better ear fixed at $+10\,\text{dB SL}$ ($20\,\text{dB HL}$).
2. Introduce the tone to the poorer ear at $0\,\text{dB HL}$ simultaneously. The patient responds (heard in better ear).
3. Increase the tone level in the poorer ear in $5\,\text{dB}$ steps while maintaining the tone in the better ear at $20\,\text{dB HL}$.
4. The lowest intensity in the poorer ear at which the patient stops responding is the Minimum Stenger Level (MSL).
5. Clinical Rule: The patient's true auditory threshold in the poorer ear is typically within $10-15\,\text{dB}$ of the MSL!

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Objective Physiological Cross-Checks

When non-organic hearing loss is confirmed or suspected, behavioral thresholds cannot be used for clinical decision-making. Objective physiological cross-checks provide unassailable proof of true auditory sensitivity independent of patient volition.

1. Acoustic Reflex Thresholds (ARTs)

• Normal ART Range: Stapedial acoustic reflexes in normal ears occur at pure-tone levels of $70-95\,\text{dB HL}$ ($70-90\,\text{dB SL}$). In sensory hearing losses up to $50-60\,\text{dB HL}$, recruitment preserves reflexes at normal absolute levels ($75-95\,\text{dB HL}$).
• The "Negative Sensation Level" Rule: An acoustic reflex cannot occur below the true behavioral threshold of an ear. If a patient claims an admitted behavioral threshold of $85\,\text{dB HL}$, but ipsilateral acoustic reflexes are robustly elicited at $75\,\text{dB HL}$ (a $-10\,\text{dB SL}$ presentation!), pseudohypacusis is definitively proven.

2. Otoacoustic Emissions (OAEs: DPOAE & TEOAE)

• Physiology: Distortion Product (DPOAE) and Transient-Evoked (TEOAE) otoacoustic emissions measure outer hair cell (OHC) electromotility within the organ of Corti.
• Clinical Cross-Check: Robust, normal OAEs (signal-to-noise ratio $\ge 6\,\text{dB}$ with reproducibility $> 70\%$) require normal middle-ear transmission and outer hair cell integrity, which occurs only when pure-tone thresholds are $\le 25-30\,\text{dB HL}$.
• If a patient produces an audiogram showing a $60\,\text{dB HL}$ sensorineural loss, but exhibits normal Type A tympanograms and robust, full-spectrum DPOAEs, a substantial sensorineural hearing loss is objectively ruled out. (Note: Intact OAEs with abnormal behavioral thresholds can also indicate Auditory Neuropathy Spectrum Disorder; verify with acoustic reflexes and ABR).

3. Threshold Auditory Brainstem Response (ABR)

• Tone-burst ABR (at 500, 1000, 2000, and 4000 Hz) provides frequency-specific electrophysiologic threshold estimation; after nHL-to-eHL correction, estimates usually fall within about $10-20\,\text{dB}$ of behavioral thresholds.
• Identification of Wave V down to $15-20\,\text{dB nHL}$ provides objective, medical-legal proof of normal peripheral and brainstem auditory pathway transmission.

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Ethical Clinical Management & De-escalation Strategy

When pseudohypacusis is identified, confronting the patient aggressively ("You are faking this test") is therapeutically counterproductive, destroys rapport, and prompts defensiveness or legal confrontation.

The "Re-Instruction Escape Hatch"

The gold standard audiologic strategy is providing the patient with an honorable, face-saving exit:

1. Pause the evaluation and remove the earphones.
2. Reinstruct using honest, neutral phrasing that does not accuse: "Some of your responses are not lining up with our other measurements, which can happen when people wait until a sound is clearly loud. Let's review the instructions: press the button for even the faintest sound you think you hear, even if it seems far away."
3. Re-test ascending thresholds starting at low intensities. This face-saving re-instruction often resolves the discrepancy without confrontation.