Conductive Hearing Loss (CHL)
Conductive hearing loss occurs when there is an obstruction or dysfunction in the sound-conducting pathways (external or middle ear), preventing sound from reaching the inner ear (cochlea).
Common Etiologies
| Anatomical Site | Common Causes |
|---|---|
| External Ear | Cerumen impaction, foreign body, otitis externa, and congenital atresia. |
| Middle Ear | Otitis media with effusion (OME), tympanic membrane perforation, otosclerosis, and ossicular chain disruption. |
| Eustachian Tube | Eustachian tube dysfunction (negative pressure causing retraction). |
Audiometric Profile
- Air-Bone Gap (ABG): Presence of a significant gap (>10 dB) where air conduction is impaired while bone conduction remains normal (representing inner ear function).
- Rinne Test: Negative (BC > AC).
- Weber Test: Lateralizes to the affected (poorer) ear.
High-Yield Exam Pearl:
In conductive hearing loss, patients often perceive their own voice as louder in the affected ear (a phenomenon known as the occlusion effect) because the sound waves cannot escape through the external canal and are instead directed to the cochlea via bone.