Changes in external ear resonance after 3 types of surgery in the patientswith chronic otitis media

OBJECTIVE, This study was designed to identify the external ear resonance c haracteristics of patients with tympanic membrane perforation and to invest igate subsequent changes in external ear resonance, depending on the length of the postoperative period and which of 3 different types of operation wa s performed: tympanoplasty with canal wall-up mastoidectomy, epitympanoplas ty, and canal wall-down mastoidectomy. STUDY DESIGN AND SETTING: A total of 227 ears of 188 patients and 96 contro l ears comprised the study. We measured the gain and frequency of the first peak of external ear resonance with a real ear analyzer. RESULTS: Gain and frequency of the first peak recorded in the preoperative group did not differ from those of the control group. However, negative pea ks appeared around I to 1.5 kHz in half of these ears. The gain increased m arkedly in all 3 postoperative groups. The canal wall-down mastoidectomy an d epitympanoplasty groups showed significantly lower frequencies compared w ith the tympanoplasty with canal wall-up mastoidectomy and control groups, but there was no difference between them. The increased gain diminished ove r time, but the peak gain did not equalize with that of the controls, even after 15 months. CONCLUSIONS: Additional gain should be considered of around I to 1.5 kHz fo r hearing aid users with tympanic membrane perforation. Postoperative chang es in external ear resonance should be expected in patients with chronic ot itis media, suggesting that fine readjustments of the hearing aid may be ne cessary.