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P. W. Flint, MD, and colleagues, at the University of Washington, Seattle, designed a study to develop a chronic perilymph fistula in an animal model. The results, presented at the annual meeting of the American Academy of Otolaryngology–Head Neck Surgery in Chicago, related the development of a chronic fistula model in guinea pig cochleas. Silicone rubber tubing was placed into the scala tympani through the round window with appropriate experimental controls. Hearing levels were documented by auditory brain-stem responses obtained one hour before fistulization and seven and 21 days after fistulization. Fistulas were confirmed by intrathecal fluorescein injections and observation of perilymphatic flow into the
middle ear space. Fistulas were found to be patent in all animals at seven days and in eight of 13 animals at 28 days. Although auditory brain-stem response thresholds increased immediately following surgery, they returned to prefistula levels by 28 days, including those animals with