Prevention and Identification of Auditory Disorders
Prevention and risk factors
This domain covers etiology, prevention, and early identification. Know noise-induced hearing loss (NIHL): typically a 3–6 kHz notch, worse at 4 kHz, with recovery at 8 kHz; metabolic and mechanical mechanisms; the equal-energy (3 dB exchange rate) and equal-pressure (5 dB) rules. Traps include confusing temporary threshold shift with permanent loss and misattributing a notch to presbycusis. Ototoxicity (aminoglycosides, cisplatin, loop diuretics), congenital CMV, and meningitis are high-yield causes; CMV is the leading non-genetic cause of sensorineural loss in children.
Screening programs
Know newborn hearing screening (OAE or AABR), the 1-3-6 benchmarks (screen by 1 month, diagnose by 3, intervene by 6), and school screening guidelines. A classic trap: OAEs are absent with even mild cochlear loss but can be present with auditory neuropathy, so AABR is preferred in NICU graduates. Also know that screening is not diagnosis.
Identification across the lifespan
Recognize red flags: asymmetric loss, sudden unilateral loss (an ENT emergency), pulsatile tinnitus, and unilateral tinnitus warranting imaging. Distinguish conductive from sensorineural patterns by air-bone gap and by tuning-fork tests (Rinne, Weber) at a conceptual level.
Worked rule of thumb: For noise exposure, permitted exposure time halves for every 3 dB increase (equal-energy). If 8 hours is allowed at 85 dBA, then 4 hours at 88 dBA, 2 hours at 91 dBA, and 1 hour at 94 dBA. A question giving a 94 dBA exposure for 2 hours implies 2× the allowable dose.