Type Ad tympanogram: is there more than known?

Abstract Objective The aim of this study was to investigate the clinical and audiological characteristics of patients with Type Ad tympanograms and to determine whether Eustachian tube dysfunction (ETD) or other non-mechanical factors might contribute to the development of this tympanometric pattern in the absence of structural middle ear pathology. Materials and methods This prospective observational study included 64 patients who presented to the otolaryngology outpatient clinic of a tertiary care hospital between December 2023 and December 2024 and were found to have a Type Ad tympanogram in at least one ear. All participants underwent a comprehensive otolaryngologic evaluation, including otoscopy, nasal endoscopy, nasopharyngoscopy, and pure-tone audiometry. Tympanometric measurements were performed using standardized classification criteria. Based on clinical, audiological, and otoscopic findings, ears were categorized into three groups: ossicular disarticulation, tympanic membrane atrophy, and cases without structural abnormalities, the latter being suggestive of functional etiologies such as ETD. Results A total of 90 ears with Type Ad tympanograms were evaluated. Among these, 70 ears demonstrated no structural pathology but had clinical features suggestive of ETD, including nasal congestion, allergic symptoms, or a history of reflux and smoking. Notably, 14 of these ears transitioned to Type A tympanograms following medical treatment, and 7 ears developed Type C tympanograms during follow-up. The evaluated ears were divided into three subgroups based on clinical and otoscopic findings: ossicular discontinuity (Group 1), tympanic membrane atrophy (Group 2), and ears with no structural pathology but clinical signs of ETD (Group 3). Conclusion Although Type Ad tympanograms are classically associated with ossicular chain discontinuity or tympanic membrane atrophy, this study demonstrates that ETD and other non-structural factors may also produce this tympanometric pattern. Recognizing these functional contributors is essential to avoid diagnostic errors and guide appropriate treatment. Longitudinal evaluation and medical management may aid in distinguishing transient dysfunction from irreversible structural abnormalities. These findings indicate a potential role of functional, reversible mechanisms such as impaired middle ear ventilation in the generation of Type Ad tympanograms.