Fistula test, Hennebert sign & Tullio Phenomenon .

Fistula test or Perilymphatic fistula test : The fistula test is performed by applying positive and negative pressure to the intact eardrum using a pneumatic otoscope or by pressing tragus.

Used to detect Perilymph fistula.

 

	Positive Result(indicates Perilymphatic Fistula)	Negative Result(Normal)
when positive pressure is applied with the pneumatic otoscope	when positive pressure is applied with the pneumatic otoscope                 + Onset of Nystagmus towards ipsilateral ear.	No changes noted.
when negative pressure is applied with the pneumatic otoscope	when positive pressure is applied with the pneumatic otoscope                  + Nystagmus also reverses & changes its direction towards contralateral ear.	No changes noted.

The type of nystagmus seen can be deducted from the picture below.

 

Ok first let me try to explain you the figure given above.

First lets take a normal person as an example ,in him when,

SCC which is stimulated	This will be the direction of slow phase of nystagmus in ear with fistula
right horizontal semicircular canal is stimulated	it causes movement of both eyes towards the opposite(left) side.
right posterior semicircular canal is stimulated	it causes downward movement of both eyes as well as intorsion of right eye& extorsion of left eye.
right anterior semicircular canal is stimulated	it causes upward movement of both eyes as well as intorsion of right eye& extorsion of left eye.
Now lets come to left vestibular system
left horizontal semicircular canal is stimulated	it causes movement of both eyes towards the opposite(right) side.
left posterior semicircular canal is stimulated	it causes downward movement of both eyes as well as intorsion of left eye& extorsion of right eye.
left anterior semicircular canal is stimulated	it causes upward movement of both eyes as well as intorsion of left eye& extorsion of right eye.

So, if  there is fistula in right ear,then

if fistula on right horizontal SCC(that means when positive pressure is applied, the right horizontal SCC will get stimulated)	when positive pressure applied via pneumatic otoscope causes slow component of nystagmus towards opposite ear . As per convention direction of nystagmus is towards fast component, therefore we say that nystagmus is towards ipsilateral ear.
if fistula on right posterior SCC	when positive pressure is applied to right ear, then according to the diagram we see that it will cause nystagmus with slow component towards downside& intorsion of eyeball. As per convention direction of nystagmus is towards fast component,  therefore we say that the nystagmus is upbeating& extorion type.

Perilymphatic fistula:

A perilymph fistula (PLF) is an abnormal opening between the air-filled middle ear and the fluid-filled inner ear. It may occur due to a defect in one of three locations:

• Oval Window –(most common site)
  • Stapedectomy surgery (for otosclerosis)
  • Head trauma or barotrauma (pressure injury)
  • Acoustic trauma
• Round window -
  • Barotrauma -- SCUBA diving, airplane pressurization
  • Congenital malformations (such as Mondini dysplasia)
• Otic capsule--

  Another possible location for a fistula is in the bone of the ear (the otic capsule). This is a rare condition where the bone between the ear and brain area is missing or thin, causing symptoms very similar to that of a round or oval window fistula. Problems in the otic capsule that may cause a perilymph fistula include:

  • Superior canal dehiscence syndrome (anterior SCC)
  • Cholesteatoma
  • Fenestration -Another type of bony fistula can occur after a surgical procedure called fenestration previously done for otosclerosis;
  • Temporal bone fracture
  • Micro-fissure

  The most common type of otic capsule fistula is located just above the superior semicircular canal and is called the superior canal dehiscence syndrome.

   

False positive fistula test(Hennebert sign)	False negative fistula test
Congenital syphilis (here stapes footplate is hypermobile, so even small pressure changes in ear, cause excessive movement of stapes footplate & excessive stimulation of utricular macule)	In Dead ear ( inner ear is damaged), there will be NO response even if a Perilymphatic fistula exists.
25% cases of Meneire’s disease. (here in 25% cases of meniere’s ,fibrous bands form connecting to utricular macule to stapes footplate)	Also seen when cholesteatoma covers the site of fistula & doesn’t allow pressure changes to be transmits to labyrinth.

 

HENNEBERT'S SIGN:

• It is a false positive fistula test i.e, when there is no evidence of middle ear disease causing fistula of horizontal semicircular canal.
• It is seen in 25% cases of  meniere's disease or congenital syphilis.
• Hennebert sign- pressure induced nystagmus &
• Hennebert symptom- pressure induced dizziness.

Tullio’s phenomenon:

Sound-induced vestibular symptoms such as vertigo, nystagmus, oscillopsia, and postural imbalance .

Tullio's phenomenon is seen mainly in:

• Superior canal dehiscence,
• Meniere's syndrome,
• vestibulofibrosis.
• other causes of perilymph fistula,
• post fenestration surgery(for otosclerosis).