Minimering af ansigtsnervestimulering i cochlearimplantater

The intra-operative group consists of patients who have met criteria for cochlear implants. We monitor the facial nerve EMG intraoperatively in all patients, and often get some facial nerve activation when we are testing the implant intraoperatively when we are looking to see if we are getting any hearing nerve responses from electrical stimulation of the implant. We will also measure the facial nerve responses for some other charge-balanced pulse shapes, which are asymmetric and in which either the positive or negative charge is expected to stimulate the nerve. We will only measure these for two electrodes, not for all 12-22 electrodes They will be then invited back post operatively for a second testing during a standard of care visit post switch on for other pulse shapes.

To measure the facial nerve stimulation threshold for one mid-array and one apical electrode of the implant using the pulse-train stimuli

The post-operative group, are patients who are actually having facial nerve stimulation on one or more electrodes, and for whom these electrodes are turned down so much they can't hear very well, or are actually turned off because of the facial nerve stimulation. For these patients, we will slowly increase the current levels on the offending electrodes (maximum of two) until they get some facial nerve twitching, and then turn down the current until they do not have stimulation any more. We will do this for all pulse shapes and determine which shape produces the greatest loudness without stimulating the facial nerve. This will be the only testing session for the second group.

To measure the facial nerve stimulation threshold for one mid-array and one apical electrode of the implant using the pulse-train stimuli

The loudness level, or auditory nerve response at which facial nerve stimulation occurs for different stimulation pulse shapes will be measured for all 24 patients on both groups and help to identify different optimal stimulus parameters.

By comparing the amount of electrical current required to initiate a facial nerve response for each pulse shape this will determine if there is an optimal type of stimulation to use, to reduce facial nerve stimulation.

This is a hugely under researched field where we are pioneering techniques and so exact outcome measures may be difficult to quantify in this scientific investigation.

We are not able to use questionnaires or scientific tools at this stage, however this can be measured through electrical current measurements on the volta software for the Advanced Bionics cochlear implant company.