Making the diagnosis
Diagnosis & tests
This is the hard part. No single non-invasive test confirms a fistula, so the diagnosis rests on a convincing history, supportive findings, and — when it matters — objective proof.
Why it is difficult
There is no simple scan or blood test that reliably proves a fistula. Doctors weigh the history (especially a trigger), the hearing test and the response to pressure, and sometimes confirm it only at surgery.
The lack of a non-invasive gold standard is the core problem and the source of the decades-long controversy.1 Objective confirmation — pneumolabyrinth on CT, a positive cochlin-tomoprotein assay, or a leak seen at surgery — is the exception rather than the rule.2
What each test contributes
No test is decisive alone. The honest hierarchy runs from a convincing history and objective markers down to the weak fistula test:
- History of a precipitantThe strongest pointer — a clear barotrauma/strain/trauma triggerdecisive
- AudiometryDocuments and tracks the sensorineural loss; fluctuation is suggestivesupportive
- Fistula test (pressure)Pressure-induced nystagmus/vertigo supports it — but insensitive and non-specificsupportive
- High-resolution CTPneumolabyrinth (air in the labyrinth) is essentially diagnostic, but rarely seendecisive
- Cochlin-tomoprotein (CTP)A specific perilymph marker sampled from the middle ear — objective but not universally availabledecisive
- Exploratory tympanotomyDirect visualisation of a leak — the historical reference standard, but invasive and observer-dependentdecisive
There is no non-invasive gold standard. History carries the most weight; pneumolabyrinth and cochlin-tomoprotein are objective but uncommon or not widely available; the fistula test is weak; and exploratory tympanotomy — the historical reference — is invasive and observer-dependent.
Audiometry tracks the loss (see VNG and the wider work-up); CT is read for pneumolabyrinth and bony defects (Role of imaging); CTP and beta-2 transferrin are perilymph/CSF markers.
Putting it together — the confidence check
Combine the strands. Objective evidence makes it definite; a trigger with characteristic symptoms makes a reasonable clinical diagnosis; symptoms alone should send you back to the differential.
Diagnostic-confidence checker
Switch on each strand that is present. Objective evidence confirms; a trigger plus symptoms makes it a clinical diagnosis.
When the diagnosis is probable and symptoms persist, exploratory tympanotomy remains the reference standard — it both confirms and treats — though it is invasive and observer-dependent.
Key points
- There is no non-invasive gold standard — the root of the long controversy.
- Objective confirmation: pneumolabyrinth on CT, a positive CTP marker, or a leak seen at surgery.
- History (a trigger) carries the most weight; the fistula test is weak and non-specific.
- Symptom-only spontaneous fistula is the weakest ground — beware over-diagnosis.