ECoG and perilymphatic fistulae: an experimental study in the guinea pig.

Perilymph fistulae present a diagnostic dilemma to the clinician. As yet, there is no readily available, widely accepted diagnostic test. Electrocochleography (ECoG), with the advent of extratympanic recording techniques, has become a clinically applicable probe of cochlear function. Clinical ECoG was used to study guinea pigs (n = 35) both before and after surgical fistulization (n = 18) or fistulization and repair (n = 17) of the round window membrane. The animals were killed, and histopathologic examination of the temporal bones was carried out 0, 1, 3, 4, 7, 10, 14, 21, and 28 days after surgery. Of the 33 animals that survived surgery, 30 demonstrated ECoG wave-forms. No significant difference between the preoperative and postoperative wave-forms could be detected. Histopathologic study showed rapid healing of the fistulae, with no evidence of hydrops. Although there appeared to be a relatively selective loss of the outer hair cells of the cochlear basal turn, autolysis precluded detailed analysis. ECoG, as performed clinically, does not appear to detect the presence, spontaneous healing, or repair of a round window membrane fistula in the guinea pig.