A 72-year-old woman complains of progressive bilateral hearing loss and difficulty understanding speech in noisy environments for the past 8 years. Otoscopy is normal. Pure tone audiometry shows air conduction thresholds of 25 dB HL at 500 Hz, 30 dB HL at 1 kHz, 40 dB HL at 2 kHz, 50 dB HL at 4 kHz, and 55 dB HL at 8 kHz. Bone conduction thresholds are 20 dB HL at 500 Hz, 25 dB HL at 1 kHz, 35 dB HL at 2 kHz, 45 dB HL at 4 kHz, and 50 dB HL at 8 kHz. Speech discrimination score is 64% at 90 dB SPL. What is the most likely diagnosis?

Explanation

## Audiogram Pattern Analysis: Presbycusis **Key Point:** This audiogram demonstrates the classic pattern of **presbycusis** (age-related sensorineural hearing loss): a gradual, progressive high-frequency slope with disproportionately reduced speech discrimination relative to pure tone thresholds. ### Distinguishing Presbycusis from Other Sensorineural Losses | Feature | Presbycusis | Noise-Induced HL | Sudden SNHL | Ototoxicity | |---------|-------------|------------------|-------------|-------------| | **Age of onset** | >60 years | Any age (occupational) | Acute (hours–days) | Variable (medication-dependent) | | **Frequency pattern** | Gradual slope, worse at 8 kHz | 4 kHz notch (dip) | Variable (often mid-high) | High-frequency (8 kHz first) | | **Air-bone gap** | Present, gradual | Present, with notch | Present | Present | | **Speech discrimination** | **Disproportionately poor** | Relatively preserved | Variable | May be poor | | **Bilateral symmetry** | Yes | Yes | Often unilateral | Usually bilateral | | **Tinnitus** | Mild, low-pitched | Prominent, high-pitched | Often present | Common | | **Progression** | Slow, insidious | Rapid initially, then plateau | Sudden | Dose-dependent | **High-Yield:** In presbycusis, **speech discrimination is disproportionately reduced** compared to the pure tone thresholds. This patient has a 64% discrimination score despite only moderate-to-severe high-frequency loss—a hallmark of presbycusis. The gradual slope from 500 Hz (25 dB) to 8 kHz (55 dB) without a notch is typical. ### Clinical Pearl The 72-year-old age, 8-year insidious onset, bilateral symmetry, normal otoscopy, and **poor speech discrimination (64%) despite moderate thresholds** all point to presbycusis. The absence of a 4 kHz notch rules out noise-induced hearing loss. ### Pathophysiology Presbycusis results from age-related degeneration of: 1. **Sensory cells** (outer hair cells degenerate first → high-frequency loss) 2. **Strial atrophy** (metabolic presbycusis) 3. **Cochlear conduction changes** (mechanical presbycusis) 4. **Neural loss** (central presbycusis → disproportionate speech discrimination loss) [cite:Dhingra 7e Ch 8; Harrison 21e Ch 428]