You likely have two injuries. You have a brain injury and you have an orthopedic injury, neck etc. If the neck is symptomatic, it interferes with blood flow to the brain. This reduced blood flow makes any brain injury much worse.

Until I resolved my neck, my brain was always bad. Once my neck started to improve, my brain issues started to get better. If I allowed my neck to get strained, my brain issues would come roaring back. My wife could tell how my days were going to be by looking at my facial composure while I was still asleep and she had just gotten up from bed. If my face had a calm look, I would have a good day. If my face had a strained look, I would have a bad day. Usually, if my face had a strained look, I was sleeping with bad posture.

I have a much improved neck today but I know that if I mess up with sleep posture, I will mess up my day. I will be foggy brained and may get headaches.

It took me two years to get my neck in a reliably stable condition. A chiro and a PT helped me along the way by helping release muscle spasms or misalignment. But, most of the healing was from strict self-discipline.

I have had sensitivity to sound for 20 years. I've been sensitive to light for over 50 years. That is easy to deal with compared to my memory dysfunction and cognitive processing issues. The foggy brain is the biggest problem but getting proper sleep in proper posture is the best solution for that.

If you still have neck symptoms, I suggest you focus on resolving them and see how you brain issues are with a stable neck.

There have been many studies that discuss the issues of blood flow to the brain and brain stem being challenged by neck issues.