My sister was a cerebral palsey, so how did she hear?
Three areas need considered:
First:
The hearing given by God for faith to be endowed comes through the word of God. They are not natural hearing ears that hang on the body and use intellect to discern sounds.
Second:
The physical aspects of cerebral palsy may or may not impact the mental acuity. Most do not have impairment or only slight impairment. A third of those with cerebral palsy do have significant impairment which brings up the third point.
Third:
I am a person who holds that the "law of God" is written upon the heart of every person who was ever born. The law has two functions. One is to let that person know they do not meet God's standard, and two, to "point" that person to the standard being met in Christ.
That understood, there is a time when a person is born where they may know the standard or right and wrong, but have not developed the cognitive awareness of personal accountability. The child may do all manner of evil, not aware or with the understanding of just how evil the evil truly is as a violation.
There is no condemnation in such a condition. Unlike human law which allows for no recognition of learning and awareness, God does not present accountability on such terms.
Therefore, the child is secure in the grace of God.