My child does not seem to understand anything you say to him. He is 21 months old and doesn't seem to even understand when you call his own name. He doesn't appear to have any hearing problems. He seems to only have one sound he makes. He doesn’t look when I point nor does he point at anything. Sometimes he seems to stare off into nothing. Up until about 13 months, he seemed to be able to communicate and had said words like mama and dada and would smile in response to stimulation but that has all stopped. He doesn’t seem to understand how to play with toys either. Why did he lose these abilities and what should I do to help him? He’s had hearing tests and the doctor said he is hearing. Now they want to sedate him to see if he is processing what he hears. I don’t know where to turn.