Today is my second, bi-lateral Cochlear implant switch on. Iím glad itís here but the wait hasnít been as difficult as the one after my first operation seven years ago. For this first switch on there was so much hope and trepidation invested in the outcome. This time Ė I know I wonít be worse off than before and hopefully the additional sound will improve the quality of my already good hearing.
Iíve already been through the switch-on process so I know what itís like. Intellectually I know my hearing nerve has to re-awaken and this is not always pleasant. I know the first day is likely to result at best in only poor sound. But despite this knowledge, there is deep inside me a hope it will be switched on and the sound will be exactly as I remember it Ė even though I know biologically this is an impossibility. So I do expect Iíll come away from this switch on, disappointed even though I know it canít be any different.
The programming commences with each electrode stimulated and I say when I can hear the softest sound. Then, once again on each electrode, I set the level for when sound becomes uncomfortably loud. After setting the threshold (low sound level or ĎTí level) and the comfort level (loudness or ĎCí level) a range of tones is played to see if any of them stand out as being too loud or soft. With programming complete it is time to be switched on.
In case there is a Ďramp up effectí, where there is very loud sound as the new processor connects with my new implant I am switched on without any stimulation to the electrodes. Immediately I hear loud high pitched screeching and a mid range roar. It is a shock, not good or pleasant and I wonder what on earth I have let myself in for. We sit - me listening to this dreadful noise to see if it changes as the processor and implant communicate. But the sounds donít change.
So stimulus is introduced to the electrodes in slow increments, to where I have set the comfort levels. The screeching doesnít seem to increase even though volume increases, which is a good sign. When someone speaks I get a pulsing in the high pitched screeching but the roar and screeching donít lessen. This pulsing does seem to indicate that the screeching and roar come from stimulus on the electrodes Ė again a good sign, even if it is unpleasant.
I am asked to put my first processor back on because perhaps both implants will work together better than just one alone. Instantly the screeching and roaring recede into the background making it bearable. What a relief! It is a hard afternoon but the best that could be expected! (Talk about disappointed Ė way beyond anything I could have dreamed of!)
The next day. Thank goodness I only have to put up with that first map for fewer than 24 hours. I am more than ready to go back for a second mapping. The place where I hear the softest sound on each electrode has moved up but to compensate, I am able to more than double the comfort level, bearing more than double the volume, meaning my dynamic range (the distance between when I first hear a sound and the level where it becomes too loud to be comfortable) has widened.
I know from experience this increase in dynamic range will help me get real understanding of speech. And this is exactly what happens. Speech is still muffled and the quality is very poor but and I am understanding 100% of speech without lip reading just 18 hours after switch on. My audiologist is stunned at the change, but I canít stress enough how poor the quality is. Muffled, nasal, distant, monotonal. This poor quality is to be expected right now Ė because it is quality which improves over time. It is quite a break through to understand speech so quickly.
With that another session is over and it is time to test my hearing in the new world. I have to wait for my husband at a shopping centre so I head for a coffee lounge. The airconditioning is such a roar I canít stand it and have to sit outside. But outside there is traffic noise! Iím startled by a large semi-trailer only to find it is a car driving past me 30í away. A jet plane takes off Ė but itís the truck Ĺ a block away on the main road. Iím wondering how anyone can live with this level of sound. My husband comes up behind me and startles me out of my chair. I have two more mappings this week so we'll see what this does for me!
The days pass quickly and each time I have a new mapping (four in the first week, two in the second and third weeks) the sound levels improve and sounds become more normal and better balanced. By the end of week two I reach a point where when Iím wearing two processors I am not constantly reminded I canít hear properly from one of them. In other words hearing from two ears sounds pretty normal.
Each session, my maps keep varying a great deal. My soft sound threshold keeps rising (and Iím not sure this is a good thing) but to compensate so does my comfort level (loudness). I have a pressure sensation along with sound from the lower frequency electrodes and programming this out takes a bit of work. Weíve even tried turning a few of them off to see if we can isolate which ones cause it. But overall this doesnít change the sound much. I can still understand speech at 100% but the quality of sound is still nasal, muffled and poor.
It will probably take three months before my map settles down and I reach a level of good quality speech. This is partly because the healing process is still in progress and partly because my brain needs to grow new neurons to deal with the new stimulus. Itís a frustrating time Ė probably more frustrating than the first time I was switched on because I know what it should sound like and I want to get there.