January 12, 2023
Electrocochleography (ECochG) testing is a measurement of the cochlea’s electrical
potentials. Typically, the measurement is defined by the stimulus onset (baseline), the
cochlear response to the stimulus (summating potential – SP), and the reaction to the
synchronised firing of nerve fibres (action potential -AP). The AP is referred to as Wave I. In
addition to being a component of the ECochG, the cochlear microphonic (CM) has its own
ECochG can be used to diagnose specific vestibular and auditory disorders. The ECochG is
predominantly used to detect Meniere’s Disease, specifically Cochlear Hydrops. For the
diagnosis of these diseases, the SP and AP amplitudes, latencies, and their connection are
utilised. Perilymph Fistula, abrupt hearing loss, and other conditions may provide aberrant
ECochG results. According to recent studies, Superior Canal Dehiscence (SCD) may also
result in higher SP/AP ratios.
- Surface electrodes are insufficient for ECochG recording. To measure the
electrocochleogram, Tiptrodes, TM-trodes, or Transtympanic electrodes are indicated.
Although transtympanic electrodes produce the most powerful response, they are
impractical for most clinics.
- Occasionally, gold foil Tiptrodes are employed, but TM-trodes provide greater
responses since they are closer to the place of production.
- Following is an illustration of preparation and electrode placement with a
TM-electrode. Note that the process must only be carried out by trained
- During the operation, the patient must lie down and be relaxed or asleep in a quiet
setting. Prior to administering the test, an inspection of the ear canal and TM is
- In order to obtain an appropriate low skin impedance, the electrode locations must
be prepped and cleansed.
- It is advised that impedance values for Tiptrodes be 5k or less. The impedance values
between two devices should be equivalent or balanced.
- The impedance of TM-trodes should be 20k or less. It may be challenging to achieve
such low impedance on the ECochG test ear electrode, and larger impedance levels
may be acceptable.
- The ECochG test leads must be utilised for waveform acquisition. Prior to placement,
the TM-trode or Tiptrode and the test ear must be prepared.
- To decrease impedance, a saline solution can be utilised. Before inserting a TM-trode,
the ear must be drained.
- The TM-trode can be immersed in a saline solution for a few minutes prior to
placement on the TM, and should be dipped in an electrode contact gel (e.g.
Sonaville) prior to placement.
- If using a Tiptrode, gently clean the ear canal with a cotton swab dipped in nuprep.
Then, apply conductive gel on the Tiptrode, squeeze it gently, and insert it into the
- ECOG is also not a test that can be performed in an environment where ear wax
cannot be removed (ie. by the technician that does evoked responses in a Neurology
- We do not believe that ECochGs performed with needle electrodes are generally a
good idea, and we recommend declining the test unless there is a valid reason to use
a needle (as opposed to a “wick” electrode) (For example, a perforation would be an
acceptable reason). We also believe that ECOGs utilising “gold tiptrodes” — a
gleaming canal electrode — are typically ineffective.
- Ensure that you have copies of the ECochG with all traces. A typewritten report is
inadequate (as there is no way to determine quality). You must observe the traces to
prove its veracity.
- You must also believe that the audiologist or technician who performed the ECOG
did not eliminate traces they did not like.
- When discarding traces that do not fit their prejudices,
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