Electrocochleography Results in Patients With Bilateral Vestibular Paresis and Sound- or Pressure-Induced Horizontal Nystagmus.

Objective: To describe the electrocochleography (ECochG) findings in patients with bilateral vestibular paresis and sound- and/or pressure-induced horizontal nystagmus.
Design: Retrospective case series.
Setting: Tertiary care center.
Patients: Three adult patients with bilateral vestibular paresis and sound- and/or pressure-induced horizontal nystagmus were evaluated from 2012 to 2016.
Main Outcome Measure: All patients underwent ECochG, vestibular evoked myogenic potential (VEMP) testing, bithermal caloric testing, rotary chair testing, audiometric testing, and temporal bone computed tomography (CT). For ECochG, the summating potential (SP) to action potential (AP) ratio was determined.
Results: All patients had normal temporal bone CT, reduced caloric responses bilaterally, decreased gain on rotary chair, and abnormal ECochG. For two subjects, the SP/AP was elevated bilaterally. One subject had unilateral SP/AP elevation. Cervical VEMPs were present in all subjects, but at reduced thresholds in two subjects.
Conclusion: SP/AP elevation was found in all three patients with the syndrome of bilateral vestibular paresis and/or sound- or pressure-induced horizontal nystagmus. As the etiology of this syndrome remains unclear, understanding the basis for abnormal ECochG may shed insight into the pathophysiology of this condition.