BEKESY AUDIOMETRY

A Complete 20-Mark Answer for RGUHS MS ENT Examination

1. INTRODUCTION AND HISTORICAL BACKGROUND

Reference: KJ Lee's Essential Otolaryngology (10th ed.) - "Historical reference: Bekesy audiometry assesses auditory adaptation or fatigue." Adams and Victor's Principles of Neurology, 12th Ed. - "Clinically, analysis has shown that there are four basic configurations, referred to as types I to IV Bekesy audiograms."

2. DEFINITION

• Hearing threshold
• Auditory adaptation (fatigue)
• Site of lesion (cochlear vs. retrocochlear)
• Pseudohypacusis (functional hearing loss)

3. PRINCIPLE

• The normal auditory system adapts slightly to ongoing sound near threshold, but continues to perceive sounds at higher intensities without significant adaptation.
• In retrocochlear (8th nerve) pathology, there is excessive auditory adaptation - an ongoing tone fades away rapidly even at suprathreshold levels.
• A continuous tone is more susceptible to auditory fatigue than an interrupted (pulsed) tone.
• By comparing the threshold tracings of pulsed vs. continuous tones, one can determine the presence and severity of abnormal auditory adaptation, thus localizing the lesion.

Reference: Shambaugh Surgery of the Ear - "Another consequence of retrocochlear hearing loss is abnormal auditory adaptation... in an ear with retrocochlear disorder, the audibility may diminish rapidly owing to excessive auditory adaptation even at higher intensity levels."

4. INSTRUMENT: THE BEKESY AUDIOMETER

┌─────────────────────────────────────────────────────────┐
│              BEKESY AUDIOMETER COMPONENTS               │
│                                                         │
│  1. Tone Generator                                      │
│     - Produces pure tones                               │
│     - Frequency sweeps: 100 Hz → 10,000 Hz             │
│     - Fixed frequency option available                  │
│                                                         │
│  2. Attenuator                                          │
│     - Automatically changes intensity                   │
│     - Rate: 2.5 dB/second (standard)                   │
│     - Range: -10 dB to +110 dB HL                      │
│                                                         │
│  3. Tone Switch                                         │
│     - Pulsed mode: 2.5 Hz (200 ms on, 200 ms off)      │
│     - Continuous mode: uninterrupted tone               │
│                                                         │
│  4. Patient Response Button (Hand-held)                 │
│     - Pressed: decreases intensity (tone heard)         │
│     - Released: increases intensity (tone not heard)    │
│                                                         │
│  5. X-Y Recording Plotter                               │
│     - X-axis: frequency (Hz)                           │
│     - Y-axis: hearing level (dB HL)                    │
│     - Records zigzag tracing around threshold           │
└─────────────────────────────────────────────────────────┘

5. TECHNIQUE / PROCEDURE

FLOWCHART: BEKESY AUDIOMETRY PROCEDURE
═══════════════════════════════════════

        PATIENT PREPARATION
               │
               ▼
    Instruct patient: "Press button
    when you hear the tone. Release
    when tone disappears."
               │
               ▼
       PULSED TONE TRACING
    (Interrupted: 200ms on/200ms off)
               │
    Frequency sweeps 250 → 8000 Hz
    Patient tracks threshold by
    pressing/releasing button
               │
               ▼
        CONTINUOUS TONE TRACING
    (Uninterrupted sustained tone)
               │
    Same frequency sweep repeated
    Patient again tracks threshold
               │
               ▼
       RECORDING OBTAINED
    Two zigzag tracings on audiogram
    paper plotted simultaneously
               │
               ▼
      COMPARE THE TWO TRACINGS
    (Pulsed vs. Continuous)
               │
               ▼
    CLASSIFY TYPE I, II, III, IV, or V
               │
               ▼
         INTERPRETATION
    → Diagnosis of cochlear/
      retrocochlear/pseudohypacusis

6. TYPES OF BEKESY TRACINGS (JERGER'S CLASSIFICATION - 1960)

VISUAL DIAGRAM OF BEKESY TRACING TYPES:

FREQUENCY (Hz) → 250    500   1000  2000  4000  8000
                 ─────────────────────────────────────

TYPE I (NORMAL / CONDUCTIVE):
dB HL
0  ─
20 ─        P and C tracings overlap / interweave
40 ─        ────────────────────────────────────
60 ─
    Both tracings coincide; separation ≤ 5 dB
    
════════════════════════════════════════════════════

TYPE II (COCHLEAR / SENSORY):
dB HL
0  ─
20 ─     P ─────────────────────────────────────
40 ─     C ─ ─ ─ ─ ─ ─ ─ ─ (drops only at high freq)
60 ─
    C tracing drops below P tracing at HIGH freq.
    Separation: 5-20 dB (usually at 1000 Hz and above)
    
════════════════════════════════════════════════════

TYPE III (RETROCOCHLEAR / NEURAL - SEVERE):
dB HL
0  ─     P ─────────────────────────────────────
20 ─
40 ─         C ─ ─ ─ ─ ─ ─ ─ (drops sharply)
60 ─
80 ─
    C tracing drops far below P tracing (>45 dB)
    from LOW frequencies onward
    Seen in: 8th nerve lesions, CPA tumors
    
════════════════════════════════════════════════════

TYPE IV (RETROCOCHLEAR / NEURAL - MODERATE):
dB HL
0  ─     P ────────────────────────────────────
20 ─         C ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
40 ─
    C tracing drops 20-45 dB below P tracing
    Uniformly across ALL frequencies
    
════════════════════════════════════════════════════

TYPE V (PSEUDOHYPACUSIS / FUNCTIONAL):
dB HL
0  ─         C ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─
20 ─
40 ─     P ─────────────────────────────────────
    
    REVERSED pattern: Pulsed tracing is WORSE than
    continuous tracing (opposite of expected)
    Pathognomonic of non-organic/functional hearing loss

7. DETAILED DESCRIPTION OF EACH TYPE

SUMMARY TABLE

TYPE I - NORMAL/CONDUCTIVE

• Continuous and pulsed tone tracings overlap or interweave within 5 dB.
• Normal auditory adaptation present; no excessive fatigue.
• Significance: Normal hearing or conductive hearing loss.
• The cochlea and nerve function normally, so no differential fatigue occurs.

TYPE II - COCHLEAR (SENSORY)

• Continuous tone tracing falls slightly below the pulsed tone tracing, especially at high frequencies (above 1000 Hz).
• Separation usually 5-20 dB.
• Reflects mild auditory adaptation characteristic of sensory (cochlear) hair cell damage.
• Significance: Cochlear lesion - Meniere's disease, noise-induced hearing loss (NIHL), cochlear presbycusis.
• At low frequencies, tracings may still overlap.

TYPE III - RETROCOCHLEAR (SEVERE/NEURAL)

• Continuous tone tracing drops dramatically below pulsed tone, beginning from low frequencies.
• Separation may exceed 45 dB - sometimes continuous tone tracing falls off the chart entirely.
• Indicates severe pathological auditory adaptation = sign of 8th nerve/retrocochlear lesion.
• Significance: Acoustic neuroma (vestibular schwannoma), CPA tumors.
• KJ Lee: "Patients with a neural lesion tend to produce continuous tone tracings more than 20 dB poorer than pulsed tracings, sometimes dramatically worse in the high frequencies (type III)."

TYPE IV - RETROCOCHLEAR (MODERATE/NEURAL)

• Continuous tone tracing falls below pulsed tone tracing by 20-45 dB uniformly across all frequencies.
• Less dramatic than Type III but still represents significant abnormal adaptation.
• Significance: Retrocochlear lesion (neural), 8th nerve pathology.
• Adams and Victor's Principles of Neurology: "Type III or IV usually indicate the presence of a retrocochlear lesion."

TYPE V - PSEUDOHYPACUSIS (FUNCTIONAL/NON-ORGANIC)

• Paradoxical / reversed tracing: Pulsed tone tracing is worse than continuous tone tracing.
• This is physiologically impossible in genuine hearing loss.
• Continuous tones are easier to track; if pulsed tones appear harder to hear, the patient is being inconsistent.
• Significance: Non-organic hearing loss, malingering, psychogenic deafness.
• KJ Lee: "A type V Bekesy tracing is suggestive of pseudohypacusis."
• Sensitivity is fair at best; now largely replaced by ABR and OAE in detecting pseudohypacusis.

8. METHODS OF PERFORMING BEKESY AUDIOMETRY

METHOD 1: SWEEP FREQUENCY (Standard/Classic)

Tone sweeps from 250 Hz to 8000 Hz continuously.
Both pulsed and continuous tracings recorded.
Total test time: ~20-30 minutes.

METHOD 2: FIXED FREQUENCY (Bekesy Comfort Level / BCL)

Tone is fixed at a specific frequency (e.g., 1000 Hz, 4000 Hz).
Patient tracks threshold for 3-5 minutes.
Specifically useful for detecting auditory adaptation at a single freq.
More sensitive for retrocochlear lesions.

METHOD 3: MODIFIED BEKESY (For Functional Hearing Loss)

Tests performed at suprathreshold levels (20-30 dB above threshold).
Patient may show Type V pattern more clearly.
Used when sweep frequency Bekesy is equivocal.

FLOWCHART: BEKESY AUDIOMETRY - CLINICAL DECISION PATHWAY

PATIENT WITH SUSPECTED SENSORINEURAL HEARING LOSS
                        │
                        ▼
              PURE TONE AUDIOGRAM
              SPEECH AUDIOMETRY
                        │
              SENSORINEURAL CONFIRMED
                        │
                        ▼
            IS SITE OF LESION NEEDED?
                        │
            ┌───────────┴───────────┐
            YES                    NO
            │                      │
            ▼                      ▼
    BEKESY AUDIOMETRY         Rehabilitation
    (+ Tone Decay Test,        planning only
     SISI, ABLB)
            │
            ▼
    ┌───────────────────┐
    │  RESULT: TYPE I   │ → Normal / Conductive → Further workup
    └───────────────────┘
    ┌───────────────────┐
    │  RESULT: TYPE II  │ → Cochlear Lesion → Audiological Rx
    └───────────────────┘
    ┌───────────────────┐
    │ RESULT: TYPE III  │ → Retrocochlear ──┐
    └───────────────────┘                   │
    ┌───────────────────┐                   ├─→ PROCEED TO:
    │  RESULT: TYPE IV  │ → Retrocochlear ──┤   ABR / BERA
    └───────────────────┘                   │   MRI IAM (gadolinium)
    ┌───────────────────┐                   │   Rule out acoustic neuroma
    │  RESULT: TYPE V   │ → Pseudohypacusis─┘   OAE (for pseudohypacusis)
    └───────────────────┘

9. ADVANTAGES OF BEKESY AUDIOMETRY

1. Automated and self-recording - reduces examiner bias
2. Provides continuous threshold record across all frequencies
3. Detects auditory adaptation - distinguishes cochlear from retrocochlear
4. Useful in occupational health and mass screening
5. Detects functional/non-organic hearing loss (Type V)
6. Can be performed without an audiologist present during the test
7. Provides a permanent graphic record for comparison

10. DISADVANTAGES AND LIMITATIONS

1. Not widely available - equipment rarely found in standard ENT clinics
2. Time consuming (~20-30 minutes per ear)
3. Requires patient cooperation and concentration
4. Not reliable in patients with severe hearing loss
5. Replaced by ABR, OAE, and MRI for retrocochlear detection
6. Sensitivity and specificity are inferior to objective tests for acoustic neuroma
7. Cannot be used in very young children (requires voluntary response)
8. Results can be affected by tinnitus (patient may confuse tinnitus with the test tone)

Reference: Shambaugh Surgery of the Ear - "All of these measures, ABLB, SISI, TDT, and Bekesy audiometry, were useful in the diagnosis of retrocochlear site in the days when tumors had to reach a substantial size before they could be diagnosed radiographically. As imaging and radiographic techniques improved, smaller lesions... could be visualized, and the utility of the classic test battery diminished. Today these measures are mostly of historic interest."

Reference: Scott-Brown's Otorhinolaryngology Head & Neck Surgery (Vol. 2) - "Nowadays, image studies and objective tests have replaced these special tests in the differential diagnosis of cochlear and retrocochlear hearing loss."

11. COMPARISON: BEKESY vs. OTHER SITE-OF-LESION TESTS

┌─────────────────────┬──────────┬──────────┬──────────┬──────────┐
│ TEST                │ Cochlear │Retrococh.│Pseudohy- │ Still    │
│                     │ Detect   │ Detect   │ pacusis  │ Used?    │
├─────────────────────┼──────────┼──────────┼──────────┼──────────┤
│ Bekesy Audiometry   │  Good    │ Moderate │   Yes    │ Rarely   │
│ ABLB (Alternate     │  Good    │   Poor   │   No     │ Rarely   │
│  Binaural Loudness) │          │          │          │          │
│ SISI Test           │  Good    │   Poor   │   No     │ Rarely   │
│ Tone Decay Test     │  Poor    │  Good    │   No     │Sometimes │
│ Acoustic Reflex     │  Good    │  Good    │  Partly  │   YES    │
│  Decay              │          │          │          │          │
│ ABR/BERA            │  Good    │ Very Good│   Yes    │   YES    │
│ OAE                 │ Very Good│  Limited │   Yes    │   YES    │
│ MRI (gadolinium)    │  N/A     │ Best     │   N/A    │   YES    │
└─────────────────────┴──────────┴──────────┴──────────┴──────────┘

12. RELATIONSHIP WITH OTHER AUDIOLOGICAL TESTS

BATTERY APPROACH (still relevant conceptually for RGUHS):

SPECIAL TESTS FOR COCHLEAR vs. RETROCOCHLEAR DIFFERENTIATION
══════════════════════════════════════════════════════════════

COCHLEAR (Sensory) LESION indicates:
  → Positive recruitment (ABLB positive)
  → High SISI score (70-100%)
  → Bekesy Type II
  → Tone decay < 25 dB

RETROCOCHLEAR (Neural) Lesion indicates:
  → No recruitment (ABLB negative)
  → Low SISI score (<30%)
  → Bekesy Type III or IV
  → Tone decay > 25 dB
  → Acoustic reflex decay positive
  → ABR: prolonged wave V latency / absent waveforms
  → MRI: vestibular schwannoma or CPA lesion

13. CLINICAL APPLICATIONS

A. Diagnosis of Acoustic Neuroma / Vestibular Schwannoma

• Type III or IV Bekesy tracing strongly suggests retrocochlear pathology.
• Should prompt contrast MRI of internal auditory meatus (IAM).
• Cummings Otolaryngology: "By retrocochlear, we mean a lesion proximal to the cochlea, the most common retrocochlear lesion being vestibular schwannoma."

B. Cochlear Lesion Differentiation

• Type II pattern with noise-induced hearing loss, Meniere's disease, ototoxicity.
• Helps guide management: hearing aids vs. further neurological workup.

C. Pseudohypacusis / Functional Deafness Detection

• Type V is specific for functional hearing loss.
• KJ Lee: "A type V Bekesy tracing is suggestive of pseudohypacusis... Even in modified Bekesy versions, a type V pattern is fair at best, both in sensitivity and in specificity."
• Now supplemented by ABR (objective) and OAE for confirmation.

D. Occupational Hearing Assessment

• Bekesy sweep frequency audiometry used for screening in noisy work environments.
• Automated self-recording makes it suitable for large-scale occupational screening programs.
• The Bekesy test (automated) remains in use for NIHL screening per recent occupational audiology protocols.

E. Ototoxicity Monitoring (Extended High Frequency Bekesy)

• Modified Bekesy protocols covering 8000-20,000 Hz used for early detection of ototoxic changes (cisplatin, aminoglycosides).

14. DHINGRA / HAZARIKA / ZAKIR HUSSAIN PERSPECTIVE (Indian ENT Textbooks)

Dhingra (Diseases of ENT, Head & Neck Surgery):

• Bekesy audiometry classified under Special Tests for Hearing (along with SISI, ABLB, tone decay).
• Described as part of suprathreshold audiometry battery.
• Five types (Jerger's classification) are standard content.
• Emphasis on its use in distinguishing cochlear from retrocochlear and diagnosing functional deafness.

Hazarika (Textbook of ENT and Head & Neck Surgery):

• Covers Bekesy audiometry under audiological investigations.
• Stresses Jerger's 5-type classification.
• Describes its role in medicolegal cases (pseudohypacusis detection).
• Notes its replacement by objective tests in modern practice.

Zakir Hussain (Clinical Manual of ENT):

• Practical description of the test for PG candidates.
• Emphasizes clinical interpretation of types for examination purposes.
• Notes auditory adaptation as the physiological basis.

Stell and Maran (Head and Neck Surgery):

• Discusses Bekesy audiometry in the context of audiological assessment for head and neck tumors, particularly CPA angle tumors.
• Types III and IV as indicators requiring radiological investigation.

15. RECENT ADVANCES (2020-2026)

A. Automated Bekesy Audiometry in Occupational Health

• Digital automated Bekesy audiometry is now integrated into modern computerized audiometric screening systems.
• Amplivox and other manufacturers use the Bekesy tracking principle in automated hearing screeners for NIHL surveillance.

B. Bekesy Comfortable Loudness (BCL) and LDL Testing

• BCL testing uses Bekesy tracking at suprathreshold comfortable listening levels.
• Combined with loudness discomfort level (LDL) for hearing aid fitting in hyperacusis patients.

C. Replacement by Objective Tests - Modern Consensus

• ABR (BERA) remains the gold standard for retrocochlear screening.
• MRI with gadolinium of the internal auditory canal has essentially replaced the entire behavioral test battery for acoustic neuroma detection.
• Sensitivity of MRI: ~99%; Bekesy Type III/IV: ~50-70% sensitivity for acoustic neuroma.
• Otosclerosis audiological assessment review (Forli et al., Acta Otorhinolaryngol Ital, 2025, PMID: 40534441) emphasizes objective audiological tests over behavioral site-of-lesion tests.

D. Digital Bekesy Audiometry

• Modern computerized audiometers can perform automated Bekesy-type tracking as part of a test battery integrated with tympanometry and OAE.
• Software analysis provides automatic classification of tracing type.
• Removes the need for the physical self-recording pen plotter.

E. Role in Low-Resource Settings

• In settings where MRI is not available, a Type III or IV Bekesy tracing remains clinically useful as a trigger for referral or further investigation.
• Still taught and examined in RGUHS and Indian PG curricula as a conceptual framework for understanding auditory adaptation.

16. MEMORY AIDS FOR EXAM

JERGER'S BEKESY TYPES - MNEMONIC: "NICE FP"

N - Normal (Type I) → N for Normal/same → both tracings overlap
I - (same) 
C - Cochlear (Type II) → C for Cochlear high freq drop
E - (same)
F - Fatal/Severe neural (Type III) → far drop from low freq
P - Pseudohypacusis (Type V) → P tracing is paradoxically POOR
(Type IV is between III and V in severity)

SIMPLER RECALL:
Type I  → "I" = Identical tracings (Normal)
Type II → "II" = Injured cochlea (mild separation at high freq)
Type III → "III" = Injury to nerve (severe, from low freq)
Type IV → "IV" = Intermediate nerve damage
Type V  → "V" = Very suspicious (functional/non-organic)

17. EXAM-ORIENTED SUMMARY TABLE

18. REFERENCES (RGUHS-RELEVANT)

1. KJ Lee's Essential Otolaryngology (10th ed.) - Behavioral Tests for Site of Lesion; Behavioral Tests of Historical Interest (pp. 310, 322)
2. Shambaugh: Surgery of the Ear - Other Behavioral Measures; auditory adaptation and diagnostic Bekesy audiometry (p. 219)
3. Adams and Victor's Principles of Neurology (12th ed.) - Special Audiologic Procedures (p. 309)
4. Cummings Otolaryngology Head and Neck Surgery - Audiometric Testing; cochlear/retrocochlear differentiation (p. 2926)
5. Scott-Brown's Otorhinolaryngology Head & Neck Surgery (Vol. 2) - Objective Tests of Auditory Function; suprathreshold audiometry (SISI, TDT, Bekesy context)
6. Dhingra PL - Diseases of ENT Head & Neck Surgery (standard Indian text)
7. Hazarika P - Textbook of ENT and Head & Neck Surgery
8. Jerger J (1960) - "Bekesy audiometry in analysis of auditory disorders," J Speech Hear Res 3:275-87 - Original classification paper
9. Forli F et al. (2025) - "Issues in the audiological assessment of otosclerosis," Acta Otorhinolaryngol Ital [PMID: 40534441]

RGUHS Exam Tip: For a 20-mark question, ensure you cover: (1) Definition and principle, (2) Technique and instrument, (3) Jerger's 5 types with diagram, (4) Clinical significance of each type, (5) Comparison with other tests, (6) Advantages/disadvantages, and (7) Recent advances/current status. The diagram of the 5 Bekesy tracing types and the flowchart for clinical decision-making are highly scoring elements.