A comparison of transtympanic and ear canal recorded electrocochleography in clinical practice

Electrocochleograms were recorded in a routine clinic on 21 patients by the transtympanic method and from a surface electrode in the ear canal. This was to determine whether a non-invasive technique would give the same clinical information as the normal transtympanic technique. Taking the transtympanic technique as the standard for comparison, the ear canal technique produced a significant number of errors in compound action potential threshold and width. The summating potential/compound action potential ratio could only be measured in just over half the ear canal recordings compared with the transtympanic recordings. From these results and a retrospective study of the notes looking at the effect of electrocochleography on diagnosis and management, it was concluded that the ear canal technique was not a substitute for transtympanic electrocochleography where the use of an invasive technique is justified.