Diagnostic Testing

To complicate matters further, there is neither an auditory or vestibular function test that will confirm the diagnosis of per-ilymph fistula. Although the simplest test in the diagnostic battery, the audiogram provides the most consistent information to consider the diagnosis of perilymph fistula. The hearing loss is usually a sloping high-frequency sensorineural hearing loss with impaired speech discrimination. Progressive sensorineural hearing loss with or without deterioration of speech discrimination is a finding that should bring perilymph fistula to the forefront of the differential diagnosis. Electro-cochleography has not been shown to enhance the ability to confirm the diagnosis, as a positive finding of the summation potential/action potential ratio of >0.5 was identified in 52% of patients with confirmed perilymph leaks.8

Vestibular function tests are oflittle value in making the diagnosis of perilymph fistula. As in endolymphatic hydrops, the degree ofdamage to the vestibular system will vary depending on the time course of the disease when the testing is performed. In a recent fistula, as in early endolymphatic hydrops, caloric testing will be normal; in an advanced stage of the disease, a caloric weakness will be present. Similarly, rotational vestibular testing will be normal in early stages and the 5 to 6 pattern of vestibular dysfunction noted on dynamic platform posturography will only be present in advanced stages of the disorder.

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