A 72-year-old man presents with a 5-year history of progressive hearing loss. His wife reports he can hear her voice but frequently asks her to repeat herself, especially in crowded restaurants. Audiometry shows bilateral symmetric sensorineural hearing loss with air-bone gap absent. The structure marked **A** in the diagram demonstrates the characteristic pattern. Which of the following is the MOST LIKELY diagnosis and the PRIMARY mechanism of hearing loss in this patient?

Explanation

## Why Option 1 (Sensory presbycusis) is correct Presbycusis is the MOST COMMON cause of hearing loss in the elderly and the MOST COMMON form of sensorineural hearing loss overall. The bilateral symmetric high-frequency SNHL marked **A** is the hallmark audiometric finding. Sensory presbycusis, caused by degeneration of outer and inner hair cells beginning at the basal turn of the cochlea (which represents high frequencies), produces an abrupt high-frequency loss with preserved low-frequency hearing—exactly matching this patient's pattern. The clinical presentation of difficulty understanding speech in noisy environments (high-frequency consonants lost while low-frequency vowels preserved) is pathognomonic. The absence of an air-bone gap confirms sensorineural etiology. This is the MOST COMMON pathophysiologic subtype in mixed presbycusis. [Cummings Otolaryngology 7e Ch 153; Dhingra ENT 7e] ## Why each distractor is wrong - **Option 2 (Noise-induced hearing loss)**: Noise-induced SNHL typically presents with a characteristic 4 kHz notch (not high-frequency sloping loss) and requires occupational or recreational noise exposure history. This patient has no such history mentioned, and the pattern is bilateral symmetric sloping, not notched. - **Option 3 (Acoustic neuroma)**: Acoustic neuroma causes ASYMMETRIC sensorineural hearing loss, often with poor speech discrimination out of proportion to pure-tone loss (retrocochlear sign). This patient has bilateral symmetric loss. Asymmetry warrants MRI of internal auditory canals, but it is NOT present here. - **Option 4 (Strial/metabolic presbycusis)**: While strial presbycusis is a valid subtype of presbycusis, it produces a FLAT audiometric threshold across all frequencies (not downward-sloping high-frequency loss). The downward-sloping curve with preserved low-frequency hearing is more consistent with sensory or mechanical presbycusis, with sensory being the most common. **High-Yield:** Bilateral symmetric downward-sloping high-frequency SNHL + difficulty hearing speech in noise + elderly patient = Presbycusis (sensory subtype most common). Asymmetry or notched pattern suggests alternative diagnosis. [cite: Cummings Otolaryngology 7e Ch 153; Dhingra ENT 7e]