A 62-year-old woman with sudden sensorineural hearing loss is evaluated. Audiometry shows high-frequency loss with air-bone gap absent. Which audiometric or clinical finding would most reliably distinguish her sensorineural hearing loss from conductive hearing loss in a patient presenting with similar symptoms?

Explanation

## Audiometric Discrimination: Sensorineural vs Conductive Loss ### Core Distinguishing Features **Key Point:** Recruitment (abnormal loudness growth) and poor speech discrimination despite adequate hearing level are hallmarks of cochlear (sensorineural) pathology and are absent in pure conductive loss. ### Recruitment Phenomenon **Mnemonic: RECRUIT** — **R**ecruitment **E**vidence **C**onfirms **R**etrocochlear **U**nderlying **I**njury **T**o cochlea - **Definition:** Abnormally rapid growth of loudness as intensity increases. - **Mechanism:** In sensorineural loss, the cochlea has reduced dynamic range. Soft sounds are inaudible, but moderate increases in intensity cause disproportionate loudness growth. - **Presence:** Indicates cochlear (inner ear) dysfunction. - **Absence:** Suggests conductive loss (normal cochlea) or retrocochlear pathology (CN VIII lesion). ### Comparison: Recruitment and Speech Discrimination | Parameter | Conductive HL | Sensorineural HL (Cochlear) | Retrocochlear HL | |-----------|---------------|-----------------------------|-----------------| | **Recruitment** | Absent | Present | Absent | | **Speech discrimination** | Excellent (if volume adequate) | Poor | Very poor | | **Tinnitus** | Rare | Common | Common | | **Vertigo** | Absent | Possible (if vestibular involvement) | Possible | | **Air-bone gap** | Present (≥15 dB) | Absent | Absent | ### Why Recruitment is the Best Discriminator **High-Yield:** Recruitment is **pathognomonic for cochlear pathology**. Its presence immediately excludes pure conductive loss (where the cochlea is normal) and points to sensorineural loss. **Clinical Pearl:** A patient with sensorineural loss may complain, "When you speak louder, it hurts my ear" — this is recruitment. A conductive loss patient will simply say, "I can't hear you," and once volume is adequate, hearing is clear and comfortable. ### Speech Discrimination in Sensorineural Loss - **Conductive loss:** Speech discrimination is excellent once the volume is turned up (the problem is transmission, not perception). - **Sensorineural loss:** Speech discrimination is disproportionately poor relative to the degree of hearing loss (the cochlea distorts sound). - **Example:** A patient with 40 dB conductive loss may have 95% speech discrimination; a patient with 40 dB sensorineural loss may have only 60% discrimination.