Purpose <p>To evaluate the utility of a novel window-damping test (WDT), which involves a simple intratympanic injection of fibrin to dampen the movement of the round window membrane and stapedial footplate, in predicting surgical outcomes for round window reinforcement (RWR) in patients with superior semicircular canal dehiscence syndrome (SSCDS).</p> Materials and methods <p>This retrospective cohort study included 8 patients with clinically suspected SSCDS. Patients underwent pure-tone audiometry, tympanometry, vestibular-evoked myogenic potential (VEMP) testing, and high-resolution CT scans with multiplanar reconstruction. The WDT involved sequential intratympanic injection of fibrin sealant components into the posterior middle ear cavity to simulate RWR, which was achieved by damping the movement of the round window membrane and stapedial footplate. RWR surgery was performed to alleviate symptoms, and symptom changes were compared between WDT and RWR.</p> Results <p>Although signs of a ‘third mobile window’ were not universally observed in diagnostic tests, WDT yielded positive results in all patients. The test effectively simulated the biomechanical effects of RWR, demonstrating even greater efficacy than surgery in most cases.</p> Conclusions <p>The novel WDT is a safe, cost-effective, and valuable preoperative tool for predicting surgical outcomes of RWR in SSCDS.</p>