Changes in External Ear Resonance after Ventilation Tube Insertion in Pediatric Patients with Middle Ear Effusion

Cho, Yang Sun; Koh, Seok Joo

Abstract

BACKGROUND AND OBJECTIVES: Middle ear effusion (MEE) is common in children, so the effects of the ventilation tube (VT) should be taken into account in prescribing hearing aids. With the ventilation tube, the external auditory canal communicates with the middle ear space, hence changing the impedance in the middle ear. This change, in turn, will have an effect on the external ear resonance (EER, real ear unaided response (REUR)). The aim of this study is to observe the effects of the tympanic membrane perforations caused by the ventilation tube on EER. MATERIAL AND METHODS:We selected 30 ears with MEE and measured EER before and after the ventilation tube insertion. We compared the EERs of the control group with the MEE group and two types of VT groups.
RESULTS
In the subjects who had middle ear effusion, the average gain of the peak resonance was larger than that of the control group. After the VT insertion, the amplitude of the gain decreased to the level of control groups, although negative gain appeared in some cases characteristically around 1000 Hz. This negative gain was observed more frequently in the VT with larger diameter.
CONCLUSION
The external ear resonance gain can be changed according to disease status or by VT insertion in patients with MEE. These changes should be considered especially in the low frequencies around 1000 Hz when prescribing the hearing aids for patients.