PP, meant to include a link
www.mitoaction.org/files/Dysautonomia.pdf

I have many of the same symptoms myself, they run in my family and DH's. I also take the same supplements and it has made a big difference in my energy and health. The ped was the one who first ran basic metabolic tests for us, when they came back wonky we found our way to Dr. Greene.

OP a few things from your post seemed like possible mild mito or metabolic issues to me - the lethargy, tone, temp and slow heart rate can all be symptoms. The head growth as well.

If you continue to have concerns I'd try to get an appointment with someone like Carol Greene at the University of MD, she is a geneticist and can cast a broad net in looking for answers. Sometimes bloodwork can be revealing, my child was low in carnitine and coq10, once those were supplemented growth and tone improved a lot.

Best to you and congrats on the new wee one.

16:18 here. High muscle tone translates to stiff, so for instance, my DS will straighten his legs so forcefully that you can't bend his knees with your hands. He'll point his toes and his feet will rotate inward. Technically he has spastic quadriplegia but his arms aren't as affected as his legs. He still clenches his fists a bit, but therapy is really helping that. CP is a broad umbrella term and the severity can differ drastically from one kid to another, much like autism. All CP parents keep their fingers crossed that their child only has mild CP, so it's quite cliche when I explain that we hope his CP is mild and only affects him physically and not cognitively as well. Our DS also wears glasses. We took him to see a pediatric ophthalmologist when he never quite grew out of the cross eyed phase seen in most newborns. It's unclear as to weather the CP contributes to his poor vision or if it's a separate issue all together. These are my experiences and I hope they help you!

My twins were born at 31 weeks. My DS was extremely rigid as a baby - through 8-9 mos - bounced on his feet on my lap all of the time. He also had torticolis. We were referred to a neurologist at Childrens who wanted to do an MRI but we declined - decided at his young age we wouldn't be doing anything different with that data. We were already getting OT and PT due to torticolis through PIE. Fast forward to 5 yr, and he still definitely has high muscle tone, but so does his dad. Other than having strong legs, he's completely normal. His twin, on the other hand, does have very mild CP (you'd never guess looking at her) - we got diagnosis around 10 mos. She was very clearly missing a number of "innate" reflexes, such as the step reflex, so she would NEVER straighten her legs when her feet touched a surface.
Are you getting OT/PT for the torticolis? Have you requested an evaluation through your parent infant education group? Are you effectively managing your son's reflux? Other than this, there's really nothing to do at this point. And fwiw, it doesn't sound at all as though anything is wrong with your DS other than that he has nasty reflux.

OP here. Thank you so much for all of this information! It's really helpful to hear your stories. It sounds like there isn't much we can know at this age and like he could be very average or could have some other issue but that it's not possible to know right now, which sort of helps me relax a bit. I'll see how things go in the coming months.

16:18 and others, what does high tone look like? I've been trying to look it up but can't find any videos or explanations. DS also arches sometimes during feedings, and we are told it's from reflux (which I think is true), but the "standing" thing I mentioned happens outside of this and has since he was very young. Sometimes if his feet touch your stomach, he will push up like he's standing and won't want to be bent into sitting. I think this is a tummy thing but don't know. It is often when he's fussy, but not always. Sometimes he will "walk" up you or on the floor like this. Thoughts?

Thank you all, and great work as parents!!

My son was diagnosed with CP at 10 months old. He went to see two different pediatric neurologists (one at KKI) and both diagnosed him with CP within minutes and the MRI confirmed the damage to his brain. He and his twin were born at 33 weeks and his prematurity is believed to have been a factor in his CP. He was a normal newborn. Slept and ate normally except he would have really severe arching of the back while feeding. The peds originally thought it was reflux so he was on zantac but it obviously didn't help much. He kind of grew out of the stiffening phase and after a few months even rolled over so we weren't concerned (the rolling eventually regressed). I thought it was strange that he never played with his feet and didn't seem as flexible as his brother, but didn't pay much attention. When his brother had been sitting for about 6 weeks, I felt that DS was definitely delayed and we reached out to Infants and Toddlers. The recommended we see a neurologist and two days later we had the diagnosis. I don't think what you're describing is like my son. He always was able to bear weight on his legs, but we now know that was due to high tone. I was told point blank by my (former) pediatrician that Caleb did NOT have CP and to stop worrying. I was blindsided when we got the diagnosis three weeks later. At the end of the day if it would put you at ease I'd go see a neurologist.