I'm an autistic parent of a kid with severe disabilities caused by a chromosome difference. Cerebral palsy was an afterthought diagnosis, a side effect, as it were, rather than the core issue. We could not get her diagnosed as autistic although she checks all the boxes, but the communication issues hit home. Several things:

1. Has he had microarray chromosome analysis done? Sometimes kids with chromosome differences have specific issues that affect language development, which can be mitigated to a degree with supplements, but which supplements depend on which genes are involved. There's a strong push that most kids who have profound language/developmental difficulties should get chromosome analysis done, in part because some of these issues can be helped through supplementing. Not a cure, but something to help ease the processing of language, the physical discomforts.

2. Has he had any metabolic testing done?

3. Are you familiar with choice hands?

Your situation resonated with me, because my kiddo has a deletion at 4q 21.1-21.3 which is associated with a complete failure of the expressive language system. It turns out that one of the biggest pieces of that is the COQ2 gene, which affects the body's production of CoQ10. A double recessive in that gene is associated with symptoms much more severe than my kid has, and supplementing CoQ10 and other supplements that work with the CoQ10 brought her language issues from profound to severe. Basically the CoQ10 deficiency was causing mitochondrial issues by mucking up the Kreb cycle. Now the Kreb cycle is an incredibly complex mitochondrial function, which can go wrong in a zillion different ways, but which is incredibly essential to the kinds of energy production that allow for complex motor control necessary for speech. Some knock-on effects of CoQ10 deficiency-caused mito dysfunction include constipation, low muscle tone, neurological problems, poor hunger/satiation signaling, poor sleep cycle signaling (for us, she would never ask to eat, then would eat until she physically couldn't, would not go to sleep without help, would then sleep until woken up...)

Anyway we were told when she was a baby that it was unlikely she would develop language, and by age 2 she had what I called a "roving 5 word vocabulary" where every time she learned a new word she'd lose an old word. Supplements helped her build vocabulary, other supplements to make those supplements work better improved her language in sudden bursts, one particular supplement I gave her an initial dose and her speech efforts went from a couple per hour to more than I could keep track of in 10 minutes.

We knew the language issues were coming, so we started with sign language very early, and sign language videos (Signing Time) taught her to read, sneakily, which we discovered by accident. Most of the non speaking people I've ever known could read. She needed adjustments for a visual deficit, but could definitely do it. She also had a talker, and PECS, and at one point, plastic versions of a bunch of foods that she could trade for the real thing. At 16 she now uses hard-to-understand speech reinforced with hard-to-understand sign most of the time, but we have conversations with her on the regular.

When there's a problem she doesn't have the words for, we use choice hands. "Are you hungry (present one flat hand) or something else? (present the other hand.) If she picks something else, we say, "Are you hurt, or is it something else" And so on, running through the usual suspects like "are your clothes bothering you, are you thirst, do you have to go to the bathroom" quickly. If she picks hurt, we start by figuring out where, then hone in on the specific problem. She can talk about frogs all day long but things like "I can't find my show on netflix" are harder to pin down.

At one point she stopped enjoying the things she normally liked, and that's communication, too. We added lecithin, in that case, and fish oil, to help her inflammation levels and neurotransmitter production (choline and omega 3s are very helpful for brain stuff.) And it helped.

Anyway, this is about mitigating the problems, not curing the kids of who they are. We've always been all about maximizing her ability to communicate and get her needs met safely.

We were able to use a combination of magnesium and vitamin c to ease the constipation down to something tolerable. A lot of laxatives can really mess with other systems, we just found the amount of mag and c that seemed to get her to a point where it wasn't hurting her. Magnesium, especially, can help a lot of systems work better.