Tympanometry and fistula test.

The 'fistula test' is performed when an abnormal opening between the vestibule and the middle ear cavity is suspected. The fistula is usually seen after stapedectomy, but may also occur after trauma to a normal ear when the round window membrane may rupture. Tympanometry with an electronystagmographic (ENG) tracing may show a positive result after stapedectomy in the absence of a fistula, and there may conversely be a normal ENG tracing after tympanometry when there is in fact a perilymph fistula. The authors explain the reasons for this paradoxical response. In no way does it detract from the value of the test, which only needs to be interpreted correctly.