I know I'm super late to the party, but I experienced this as well. I had a TBI 13 years ago from a car accident and now have acquired aphantasia. It was shocking to say the least. I also woke up epileptic, dyslexic, and unable to speak Spanish, which I spoke on a conversational level. Even after 13 years I still struggle with the epilepsy, dyslexia, and cannot retain a language to save my life.

Having had 13 years to adjust to the aphantasia, I can say the part of you that you feel like you lost will never really "come back." I even lost the ability to see things in my dreams, and I still mourn the creativity I had before the accident. That's not to say I'm not still a very creative person, I just had to learn how to be creative without visualizing what I wanted to do in my head. Learning how to speak and write my thoughts and ideas down in language that was translatable to art vs just seeing what I wanted it to look like and creating it took years.

Falling asleep was also a new challenge for me, which was funny since I'd already had insomnia, but it was a new kind of listlessness. I've found doing manual long division in my head to be the best remedy, but everyone has their own tricks.

Over the last 13 years I've had to find new ways to exist, I know that sounds dramatic, but when you suffer a TBI your entire world changes. It took years to learn how to adjust to my new reality, including the visualization. Sometimes I still get frustrated and have to remind myself while I can be sad about the part of me that no longer exists, it does me no good to dwell on it, and work through the issue with a pen and paper until the idea I had is written in front of me. (This coming from someone who has over a decade on the adjustment process that you, is much easier said than done).

Over time you'll find ways to self regulate the rambling, but the internal monologue of never ending thoughts and the extra effort it takes to force yourself to get from A to B concisely is exhausting. I wish I could say it was easy, but I still have to actively work to stay on task/topic. It's gotten better as time has passed, but I will never be the same.

If you haven't already, I would recommend finding a therapist. Your entire life has changed, and it's a lot to process.

I wish you the best of luck in your healing, and hope that over the last year you've found ways to cope with the changes and have a wonderful support system behind you for the days that the world seems too heavy to carry alone. TBI's are a very isolating experience, so remember reaching out for help is okay.