How did Marlee Matlin become deaf

I look on the internet like many people do in fact over 220 million searches a day a done and increasing all the time.

One question I would like to know the answer to is: How did Marlee Matlin become deaf?

Someone on the internet will know the answer and for the benefit of hundreds of other it would be good to get the answer.

If someone could post it here this would be grateful for hundred of people.