The Role of Occlusion of the External Ear Canal in Hearing Loss

Özet

Objective: The objectives are to determine and compare the degrees of hearing loss upon occlusion of thecartilaginous and the bony portion of the external earcanal (EAC).Methods: There were 20 healthy participants withnormal ears, and all gave an informed consent. Afteran otoscopy, a baseline pure tone audiogram (PTA)was conducted. If the PTA of the participant was normal, aqueous cream was applied with a syringe via an18 G cannula, from the tympanic membrane up tothe isthmus which corresponds to the bony ear canal. A second PTA was conducted, and subsequentlythe cream was removed via suction under microscopeguidance. The procedure was then repeated with thecream applied from the isthmus to the aperture of theexternal ear canal using the same cannula followed bya PTA and removal of cream under microscope.Results: The mean threshold difference of occlusionat both portions of the ear canal were compared andanalyzed. The mean threshold difference of hearingloss upon occlusion at the cartilaginous EAC was37.5 to 48 dB. The mean threshold difference of hearing loss upon occlusion at the bony EAC was less,with a range of 21 to 24.95dB. There was a statisticaldifference (p<0.05) in the hearing loss between theblockage of the cartilaginous canal versus the blockage of the bony canal with a maximum difference at2kHz.Conclusion: Cartilaginous block of the external earcanal causes more hearing loss than block of the bonyear canal. This correlates with the concept and properties of sound waves, resonance and impedance.