Noise-induced sensorineural hearing loss (NIHL) preferentially affects which frequency on pure tone audiogram, and what pathological change underlies this?

• A 4000 Hz (4 kHz notch); hair cell damage occurs maximally at the basal turn of the cochlea (which processes high frequencies) ~10 mm from the oval window due to resonance energy concentration ✓
• B 250 Hz; low-frequency hair cells at the apex of the cochlea are most metabolically active and vulnerable
• C 1000 Hz; mid-frequency hair cells at the middle turn are damaged first by mechanical vibration
• D 8000 Hz; extreme base of the cochlea receives the highest vibrational energy from all sounds

Explanation

NIHL classically produces a '4 kHz notch' on PTA — a dip in hearing threshold at 4000 Hz with partial recovery at 8000 Hz (the 'hockey stick' appearance). The 4 kHz area of the basal cochlea is maximally damaged because: (1) resonance of the outer ear canal amplifies sounds in the 2-4 kHz range, (2) blood supply is less efficient in this region, (3) outer hair cells (especially the first row) are most vulnerable due to their metabolic activity for amplification. The underlying pathology is stereocilia fusion, disruption of tip links, and ultimately OHC apoptosis from metabolic exhaustion and ROS generation.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.