A positive finding usually indicates the patient has eroded horizontal semicircular canal, through which the pressure is being transmitted to the labyrinthine fluid and stimulating macula and ampullary crests.

 

Why is specifically horizontal semicircular canal affected?

 

Horizontal semicircular canal lies in close relation to the tympanic cavity or the middle ear cavity, so it’s wall is more vulnerable to erosion and fistula formation than other parts of the labyrinth due to disease processes or cholesteatomas in the tympanic cavity.

 

But a negative finding here doesn’t exclude the possibility of fistula. It can be negative also in the case of a non-responsive labyrinth or dead labyrinth so that large change in pressure also can’t stimulate it to cause a nystagmus or vertigo.

 

What can cause non-responsive or dead labyrinth?

 

Among many causes most common are –

  1. Infection

      2. Treatment of Meniere’s disease

 

 

Further information

A. What is Fistula test?

B. There are two exceptions related to fistula test which appear as false positive findings

 

  1. In congenital syphilis, the stapes footplate is very mobile. So it acts as a piston and allows large fluctuation of pressure in the tympanic cavity to get transmitted to the labyrinth.
  2. In Ménière’s disease, fibrous bands are formed inside the labyrinth and some of these bands connect the stapes footplate to the macular structures. When stapes moves they stimulate the macula.

 

 

✨  Note

We continuously update our articles by consulting with the author and changes in recent guidelines of the exam. Please make sure you are subscribed to our newsletter (it’s completely FREE) to get notified on future updates of this article.

 

📚  Write an article today

The Paradigm Shift Group is a community website, where everyone can publish materials related to study. The goal is to provide high quality FREE study materials created, edited and studied by academic people (students, researchers and professionals). You find more information on this page. Email the article to theparadigmshiftgroup@gmail.com or admin@theparadigmshiftgroup.com.

3 Comments

  • Reshma Reply

    I think there should be a link in the”What is fistula test?” in further information… Probably some technical issue. 😊

    • Arnab Mukherjee

      Thank you Reshma for informing us about the problem. Now it is corrected.

Feel free to comment here,