Presbyacusis (age-related hearing loss) primarily affects high-frequency sounds first. Which part of the cochlear basilar membrane is responsible for high-frequency sound perception, and what is its anatomical characteristic?

• A Apex (helicotrema end) — wide, loose, low stiffness
• B Middle turn of cochlea — intermediate stiffness for mid-range frequencies
• C Basal turn where the basilar membrane is widest — responsible for low frequencies
• D Base (oval window end) — narrow, stiff, high resonant frequency ✓

Explanation

The basilar membrane of the cochlea is tonotopically organised (place theory). At the base (near the oval and round windows) it is narrow (~0.04 mm) and stiff, with high resonant frequency — encoding high-frequency sounds (>4000 Hz). At the apex (helicotrema end) it is wide (~0.5 mm) and lax/loose, resonating to low frequencies. Presbyacusis predominantly affects the basal turns (high frequency) due to hair cell loss and strial atrophy. This is the anatomical basis of the audiometric high-frequency notch seen in presbyacusis.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.