Pseudomembranes and Tissue Plugs in the Round Window Niche: Implications for Inner Ear Drug Delivery

Objective: To determine the prevalence of anatomic obstructions, including pseudomembranes and tissue plugs, in the round window niche among human temporal bone specimens. To identify patient factors associated with these obstructions. Background: Effective drug delivery to the inner ear is critical for intratympanic and emerging intracochlear therapies for sensorineural hearing loss (SNHL). Both rely on access to the round window membrane (RWM), which may be obstructed by pseudomembranes or tissue plugs that impair therapeutic efficacy. This is the largest survey to date of RWM obstructions and their associated factors. Materials and methods: Temporal bone specimens with SNHL and normal hearing were selected from Massachusetts Eye and Ear, University of Pittsburgh, and Hospital Nacional de Niños using the NIDCD National Temporal Bone Registry. Exclusion criteria included prior otologic surgery, middle ear disease, and congenital anomalies. Histopathologic analysis was performed. Results: Two hundred seventy-nine temporal bones were analyzed (215 SNHL, 64 controls). Among adults, 43.2% had pseudomembranes and 19.2% had tissue plugs. Among children (age ≤18), 10.0% had pseudomembranes and 50.0% had tissue plugs. Results did not differ by hearing status. Pseudomembranes were significantly associated with age older than 18 [odds ratio (OR): 8.01] and reactive middle ear mucosa (OR: 1.83). Tissue plugs were associated with age 18 or younger (OR: 9.03) and presence of mesenchyme (OR: 2.53). Meniere disease (OR: 0.07) and ototoxicity (OR: 0.11) were associated with fewer pseudomembranes. Conclusions: RWM obstructions are common, with pseudomembranes or tissue plugs present in 2/3 of ears. Adults were more likely to have pseudomembranes, while children were more likely to have tissue plugs. These findings may impact inner ear drug delivery strategies.