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The role of the Audiologist during cochlear implant (CI) surgery

When you undergo your cochlear implant or auditory brainstem implant (ABI) surgery, a CHi audiologist will also be in the theatre to conduct what’s known as “intra-operative monitoring”. This means that the audiologist will use a variety of sophisticated hardware and software tools to ensure that the implanted device (electrode array) is working property, and that it is placed in the optimal position to deliver the best possible result.

Intraoperative monitoring measurements can also provide a valid basis for initial programming (MAPping), especially in cases involving very young children or those with multiple disabilities where programming the device can be difficult.

The role of the Audiologist during cochlear implant (CI) surgery

The monitoring starts even before the electrode array is opened. This is to ensure that it is not faulty. Only once this has been ascertained, will the device be handed to the surgeon.

After the surgeon has inserted the electrodes and placed the device, the audiologist will conduct an Impedance Field Telemetry (IFT) test. This check allows:

• measurements to see how well each electrode is working
• ensuring that there are no short and open circuits between electrodes
• determination of the intra-cochlear voltage distribution as this can affect the ultimate outcome and degree of success of the implant surgery
• another check that all electrodes are working properly

By doing these checks in the operating theatre and being able to detect faulty electrode insertion, or electrode malfunctioning or a failed receiver-stimulator, allows your surgeon to take immediate steps to fix any issues while you are still under anaesthesia, reducing the likelihood of you having to undergo a second surgery at a later stage to address the problem.

Next, the Audiologist will perform ART (Auditory Nerve Response Telemetry) measurements, recording the electrical compound action potentials (ECAP). These are the small voltage changes that are created by the auditory nerve when it transmits a signal to the brainstem. ECAP measurements can be used to assess the response of your auditory system to electrical stimulation immediately after the CI electrode has been inserted in your cochlear.

The role of the Audiologist during auditory brainstem implant (ABI)  surgery

An Auditory Brainstem Implant System (ABI) is a sophisticated hearing implant system for individuals with hearing loss due to a non-functional auditory nerve. Bypassing the inner ear and auditory nerve, it stimulates the cochlear nucleus (CN), thus providing patients with a variety of hearing sensations to assist with sound awareness and communication.

After the surgeon has positioned the ABI placing electrode, the audiologist performs IFT and Electrically Evoked Brainstem Response (EABR) measurements. EABR is a measurement of the auditory brainstem response to electrical stimulation instead of auditory stimulation. In addition to helping to assess neural integrity, EABR can be used to test if a patient will benefit from an implant and if the implant is working.

Several placements may be needed before appropriate responses are obtained. After responses are obtained, the placing electrode is removed and the bed for the implant housing is prepared. Before the active electrode is fixed, a final EABR recording using the active electrode is performed.