1. Electrocochleography (ECoG). ECoG is an electrophysiologic test of cochlear function. Conditions such as Ménière's disease, which are characterized by endolymphatic hydrops, demonstrate an elevated summating potential to action potential (SP/AP) ratio on electrocochleography (ECoG). An increase in the SP relative to the AP is thought to be due to a deflection of the basilar membrane position toward the scala tympani. Accordingly, abnormal ECoG has been correlated with the finding of cochlear hydrops (in the basal turn) on gadolinium-enhanced MRI.