A 38 years old man had labyrinthine fistula with positive fi

[meenaxi]

A 38 years old man had labyrinthine fistula with positive fistula sign. Two weeks later fistula sign became negative without any treatment. Which of the following will be the Rinne’s test (tuning fork) finding?
a- True-positive Rinne’s test
b- False-positive Rinne’s test
c- True-negative Rinne’s test
d- False-negative Rinne’s test

[meenaxi]

Ans: d.

It is seen in severe unilateral SNHL. Patient does not perceive anty sound of tuning fork by air conduction but responds to bone conduction testing. This response to bone conduction is actually from the opposite ear because of transcranial transmission of sound. In such cases correct diagnosis can be made by masking the non-test ear with Barany’s noise box while testing for born conduction. Weber’s test will further help as it gets lateralized to the better ear.
In this case after two weeks the damage to Cochlea has made labyrinth dead leading to severe SNHL which has made the Fistula sign Negative.

Fistula test: The basic of this test is to induce Nystagmus by producing pressure changes in the external canal which are then transmitted to the labyrinth. Stimulation of the labyrinth results in nystagmus and vertigo. Normally the test is negative because the pressure changes in the EAC cannot be transmitted to the labyrinth.

Positive Fistula Test is seen in:
1. Erosion of horizontal semicircular canal (Cholesteatoma or fenestration operation)
2. Abnormal opening in Oval window (post stapedectomy fistula) or Round window (rupture of round window).
A positive Fistula test also implies that the labyrinth is still functioning.

False-negative Fistula test: Dead labyrinth, Cholesteatoma covering site of fistula.

False-positive Fistula test (Positive fistula test without Fistula): Congenital syphilis, 25% cases of meniere’s disease (Hennebert’s sign).