April 26, 2017
By: Prajakta Bhogte and Shefali Shah
Switch-on of a cochlear implant or Device Activation as it is sometimes called is a much awaited event for parents and families of children with hearing loss who have chosen to cochlear-implant their child. In our observation at Sound Steps, switch-on becomes a defining moment for every family that we have ever had the privilege to have worked with: in their minds, it determines how their child’s life is going to play out. The reality is that switch-on or device activation is not a predictor of how quickly a child with hearing loss is going to understand spoken language and talk. There are children who have had unremarkable switch-ons and yet have gone on to make steady progress in their journey towards age-appropriate spoken language development.
What does Switch-On or Device Activation mean?
Switch-on is the process of connecting the external sound processor to the child’s internal (surgically placed) cochlear implant. From the day of switch-on or device activation, the child starts getting electrical stimulation. Your child’s audiologist will determine the amount of electrical stimulation to give your child based on several factors such as the physiology of your child’s internal structures and his or her behavioural responses. You will realise the influence and importance of the pre-implant training that your child and your family received as you observe the reliability of your child’s responses to electrical stimulation at switch-on.
How soon can my child be switched-on?
As surgical techniques have become more refined, the size of incision made by surgeons during cochlear implant surgery has become significantly smaller. As a result, the healing process is shorter and there is no longer that six week wait period following surgery, during which your child remains without sound. In India today, the healing process in the absence of complications, takes between six to ten days. At Sound Steps, the date for switch-on is finalised after our families have obtained written permission from their E.N.T. surgeon for switch-on.
What happens at Switch-on?
Your child’s audiologist will explain the different steps that s/he will be taking your child through as s/he proceeds to activate your child’s Sound Processor. Broadly speaking, at switch-on, your audiologist will be doing the following, allowing for some variations in light of the different manufacturers of cochlear implants and the model of your child’s Sound Processor:
1. Checking impedance:
Electrodes when inserted into the cochlea create impedance (opposition due to the cochlear fluid). Impedance values at each electrode tell us about the status of the electrode.
2. Checking NRTs or NRIs:
NRTs or NRIs are the responses to the current delivered through the implant, by neural fibres in the cochlea. As this procedure is not dependent on your child’s participation, your audiologist will keep your child busy in an activity of interest while NRTs or NRIs are being measured.Your child may or may not respond to the stimulation which s/he is being given through the electrodes, during this procedure. It is important for you to understand that absent NRTs/ NRIs do not mean that the cochlear implant is malfunctioning.
3. Electrode activation:
Once your child’s audiologist gets NRTs or NRIs, s/he will start giving electrical stimulation through a range of electrodes or through a selected bunch of electrodes. You may or may not observe a response to this initial level of stimulation. Your child’s responses which may range from searching for the sound, smiling in response to the stimulus or a change in eye gaze will guide the audiologist as s/he adjusts the level of stimulation. Some children have cried at switch-on as they adjust to this new experience.
Your child's audiologist will set 'C' levels (i.e. comfort levels) or 'C' and 'T' levels (i.e. threshold levels) at switch-on. The audiologist will also check and observe your child's responses to Ling's six sounds.
4. Tolerance Level:
Before giving this switch-on MAP to your child, the audiologist will check your child’s tolerance to loud sounds in order to check that your child is not getting overstimulated. At Sound Steps, mothers are encouraged to sing along as both parents keep time by playing on musical instruments.
What happens next?
Your child will go home with his or her switch-on MAP. Over the next MAPping appointments, your audiologist will refine your child’s MAP as s/he learns to pay closer attention to this new sound experience.
What is a MAP?
Your audiologist will give you a copy of your child’s switch-on and of every subsequent MAP for your records (if the software allows). Your child’s onward journey with Spoken Language will require his or her Auditory-Verbal Therapy sessions to be closely integrated with the MAPping schedule and speech perception testing in Audiology.
Your child’s march towards independence will be accelerated as both your audiologist and therapist partner you and your family on this very special journey. Enjoy!