The following excerpt is taken from Chapter Six of Pervasive Developmental Disorders: Finding a Diagnosis and Getting Help by Mitzi Waltz, copyright 1999 by O'Reilly & Associates, Inc. For book orders/information, call (800) 998-9938. Permission is granted to print and distribute this excerpt for noncommercial use as long as the above source is included. The information in this article is meant to educate and should not be used as an alternative for professional medical care. 

The best approach to working with non-verbal, barely verbal, or Apraxic children and adults is what some speech therapists call "Total Communication." It involves relying not only on oral language to build communication skills, but introducing gestures, sign language, and other visual communication systems even as you do speech therapy. A person who cannot communicate is cut off from others, and it has been conclusively shown that visual communication systems use the same brain circuits as oral communication does. In other words, using visual communication may help build up these weak circuits, laying the groundwork for oral speech. The goal of the SLP in this situation is to help the person transition from the visual to the verbal, first by making the connection between the two, and then by doing traditional speech work. Most experts in helping people with communication disorders endorse the Total Communication approach.

There is research that teaching speech and sign language at the same time will increase the likelihood that the child will speak.  Unfortunately, many behavior therapists teach only speech because they feel that sign language will become a crutch, and the child will rely on signs rather than speaking. There is no evidence to support this notion.

Interestingly, when a person talks or uses sign language, the same area of the brain is activated. Thus, the procedure of teaching speech and sign language simultaneously may, in fact, be stimulating two neurological pathways that activate the same area of the brain.  

Even Dr. Lovaas, who has long pushed a "speech-only" approach, is beginning to come around to the Total Communication point of view. If children in an intensive ABA program still have not initiated speech after a long time, he now recommends using PECS symbols or something similar to jump-start communication, according to parents.