Perilymphatic Fistula

A perilymphatic fistula (Latin: fistula perilymphatica) is an abnormal communication caused by a tear or defect in the membranes that separate the perilymph-filled inner ear from the middle-ear cavity. The defect most often involves the round window (cochlear window) or the oval window (vestibular window).

As a result, perilymph may leak from the inner ear into the middle ear. The associated fluid loss and pressure disturbance within the labyrinth can impair both auditory and vestibular function, producing a characteristic symptom pattern that is often intermittent.

Aetiology and Pathophysiology

A fistula typically results from an abrupt pressure gradient between the inner and middle ear that leads to rupture of a labyrinthine membrane.

Main causes:

• Trauma:
  • Head trauma: This is most often associated with a temporal bone fracture.
  • Barotrauma: This may follow rapid changes in ambient pressure (e.g., flying or diving) or a sudden rise in intrathoracic pressure (e.g., forceful coughing, sneezing, or straining during a Valsalva maneuver).
  • Acoustic trauma: This can occur after exposure to extremely intense sound.
• Iatrogenic injury: This may occur as a complication of ear surgery, particularly stapes surgery (stapedectomy or stapedotomy).
• Congenital anomalies: Structural inner-ear malformations may predispose to membrane rupture.
• Spontaneous onset: In some cases, a fistula develops without a clear precipitating event.

Symptoms are thought to arise because perilymph leakage disrupts the inner ear’s normally closed, pressure-stable system. As a result, the labyrinth may become abnormally sensitive to pressure changes that would not otherwise affect vestibular or auditory function.

Clinical significance

Perilymphatic fistula typically presents with a fluctuating combination of vestibular and auditory symptoms.

Main symptoms:

• Vestibular symptoms:
  • Episodic spinning vertigo (true rotational vertigo).
  • Imbalance and unsteady gait.
  • Tullio phenomenon: vertigo and nystagmus triggered by loud sound.
  • Hennebert sign (fistula test): vertigo induced by pressure changes in the external auditory canal (for example, by pressing on the tragus).
• Auditory symptoms:
  • Fluctuating sensorineural hearing loss: hearing that may temporarily worsen or improve.
  • Ringing or noise in the ear (tinnitus).
  • Aural fullness (a sensation of ear pressure or blockage).

Diagnosis can be challenging. It is based on the clinical history together with audiologic assessment and vestibular testing. The diagnostic “gold standard” is exploratory tympanotomy, which allows direct inspection of the middle ear and a targeted search for a perilymph leak.

Treatment may be conservative or surgical. Conservative management focuses on strict activity restriction, including bed rest and avoidance of straining or exertion. If symptoms persist or are severe, surgical management is considered. This typically involves tympanotomy with sealing of the suspected leak site using a soft-tissue graft, such as fascia or adipose tissue.

Differential Diagnosis

Perilymphatic fistula often mimics other inner-ear disorders and is therefore frequently misdiagnosed. The most important differential diagnosis is Ménière’s disease, which can also cause episodic vertigo, tinnitus, and fluctuating hearing loss. With a fistula, however, symptoms are more likely to be provoked by exertion, straining, or pressure changes. Other conditions to consider include vestibular neuritis, benign paroxysmal positional vertigo (BPPV), and superior semicircular canal dehiscence syndrome.