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Summating potential/action potential ratio in perilymph fistula.
1Department of Otorhinolaryngology, University of Texas Southwestern Medical Center, Dallas 75235-9035.
Summary
Electrocochleography can help predict perilymph fistula and endolymphatic hydrops. An abnormal summating potential/action potential (SP/AP) ratio suggests inner ear fluid imbalance, aiding diagnosis.
Area of Science:
- Otolaryngology
- Neuroscience
- Audiology
Background:
- Perilymph fistula is a challenging diagnosis.
- Electrocochleography measures inner ear electrical activity.
- The summating potential/action potential (SP/AP) ratio is a key electrocochleography metric.
Purpose of the Study:
- To evaluate the predictive value of electrocochleography for perilymph fistula.
- To correlate SP/AP ratio abnormalities with surgical findings and outcomes.
Main Methods:
- Prospective study of 144 patients with suspected perilymph fistula.
- Electrocochleography performed on all patients.
- Exploratory tympanotomy conducted on 34 patients (39 ears).
Main Results:
- 10 of 19 ears with normal SP/AP ratio had perilymph fistula.
- 16 of 20 ears with abnormal SP/AP ratio had confirmed perilymph fistula.
- 18 ears with abnormal SP/AP ratio showed symptom resolution after grafting.
Conclusions:
- An abnormal SP/AP ratio predicts both endolymphatic hydrops and perilymph fistula.
- Abnormal SP/AP ratio is specific but not sensitive for inner ear fluid imbalance.