Electrocochleography
Under electrocochleography , abbreviated ECochG , is meant a method of examination of Otorhinolaryngology for measuring potentials , the response to auditory stimuli inside the worm ( cochlea are generated).
The measured electrical activity occurs within 1–3 milliseconds after the acoustic stimulus (click noise or short tone, so-called tone burst). For the measurement, an electrode must be brought as close as possible to the cochlea, i.e. in the external auditory canal near the eardrum or - much better, but invasive - a needle electrode through the eardrum to the promontory .
There are three different potentials measurable, namely that
- Microphone potential (cochlear microphonic, CM), which roughly corresponds in shape to the triggering stimulus and is regarded as the stimulus response of the outer hair cells, the
- Summation potential (summa ting potential, SP), which is also attractive synchronously and the basilar membrane is interpreted as an expression of nonlinear oscillations and the
- Cumulative action potential of the auditory nerve (compound action potential, CAP, AP; German also abbreviated to SAP), which is also dependent on the stimulus strength and which is identical to the first wave (I) of the curves in brainstem audiometry .
A high negative SP amplitude is seen as an expression of endolymphatic hydrops in Menière's disease , with the ratio of the summation potential to the summation action potential (SP / CAP quotient) being evaluated. In principle, the ECochG, like the brain stem audiometry ( BERA ), can also be used to determine the hearing threshold.
literature
- Martin Kompis: Audiology . 4th edition. Hogrefe, Bern 2016, ISBN 978-3-456-85553-0 , p. 187 .