Investigation of endolymphatic hydrops by electrocochleography in patients with Cogan's syndrome

We compared auditory and vestibular function between a patient with typical Cogan's syndrome and a patient with atypical Cogan's syndrome. Repeat audiograms demonstrated fluctuating sensorineural hearing loss in the affected ear. Brainstem auditory evoked response testing revealed no abnormalities. Hallpike caloric testing showed a decreased response in the affected ear in the typical case and responses within normal limits in the atypical case. Sinusoidal harmonic acceleration was normal in the typical case, and there was an abnormal phase at 0.01 Hz in the atypical case. Endolymphatic hydrops was investigated by electrocochleography. In both patients, there was an enhancement of the summating potential, with an increased ratio of summating potential to action potential amplitude. This finding is consistent with endolymphatic hydrops.