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User guide
ELI O S
ECH001XN111-A4 – 07/2022
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Introduction and test setup 3.2 ECochG
3.2 ECochG
ECochG : ElectroCochleoGraphy
Among the Auditory Brainstem Response, we group together the Brainstem Auditory Evoked Potentials ( ABR ) and the
Cochlear or Electrocochleographic potentials ( ECochG ). Traditionally, ECochG was carried out under anesthesia using a
trans-eardrum invasive electrode placed on the promontory. Thanks to its know-how in the field of electrophysiological
measurement,
ECHODIA was able to develop a technique usable on a routine basis, without anesthesia and in a non-invasive
manner, using an electrode covered with a fine film of gold, delicately inserted into the outer ear canal.
Cochlear potentials include the Cochlear Microphonic Potential (CMP), the Summation Potential (SP) and the Action Poten-
tial(AP).
The CMP, particularly characteristic because of its sinusoidal aspect, reflects the contracting of the outer hair cell when
encountering an acoustic stimulation. It is easily identifiable by the use of a constant priority click (rarefaction or condensation
click). Neglected at length by electrophysiologists, and wrongly considered as an artifact, CMP was erased from the traces
by the abusive use of alternating click polarity.
AP has 2 particularly ample negative components N1 with a culmination time of around 1.5 ms and a component N2. Com-
ponent N1 of the AP corresponds to wave I recorded in
ABR . N1 is generated by the distal portion of the auditory nerve.
The SP is not sensitive to the stimulation polarity. It is relatively characteristic because it consists of a stepped negative
deflection based on the component N1 of the AP. The SP is a complex multicomponent electrical signal on which the nature
of the generators has not yet been clearly established.
As a complement to ABR , ECochG can be used for highlighting a wave I which is difficult to identify on ABR traces,
research into hearing thresholds, research into a residual cochlear activity (as in the case of a cochlear implant balance), for
evaluating the cochlear function for auditory diseases (CMP's present, flat
ABR's ), per-operatory monitoring in surgery of
the acoustic neuroma. One of the current indications of the ECochG is the evaluation of the SP/AP ratio which is increased
in pathologies associated with endolymphatic hydrops disease.
3.2.1 Equipment
To make ECochG measurement you will need the following equipment:
ELI O S
unit E
CHO
-
DIF
unit
Electrophysiology
cable with accessories Insert earphone
2 electroacoustic tubes
2 surface electrodes