Parents are very concerned when their child is not speaking. That's one of the reasons why they come into the pediatrician's office or get referred to a developmental specialist like myself. The differential diagnosis is often initially worked on by the primary physician. And one of the first concerns is, "is my child not hearing, and that's why they are not speaking?" So that hearing evaluation usually gets done, and it's fine. A differential diagnosis or other possible causes for that is something known as mutism. The children choose not to speak to particular people. They may have speech delay, but it's almost a selective or elective mutism. Choosing not to speak, maybe in school or when other people are around, but only to a few members of their family or friends.
That needs to be differentiated because a child who is non-verbal and in the autism spectrum has a different diagnosis, whether they have just apraxia, they’re not being able to make sounds or they truly do not have any verbal language that is available for them has not been developed. There can be non-verbal communication which can be worked with and developed on. These are the kids who would benefit from early picture exchange communication system. Much that verbal therapy and verbal prompting should be continued to help develop that. This is an area that a lot of people even want to think of differentiating a child who had speech and language, and then lost it, and "is this probably Landau-Kleffner syndrome?" Doing a good thorough history and differential diagnosis is important when you have a child who is not speaking. It can be associated with autism but also seen in other conditions.