A really good resource is this site:

What is the Ketogenic Diet? A Comprehensive Beginner's Guide

A great book, which I only got to a few pages of and skimming before borrowing to someone else:

The Ketogenic Bible: The Authoritative Guide to Ketosis: Jacob Wilson, Ryan Lowery: 97816286146: Amazon.com: Books

I would start with those, but as far as support groups and other places to get good info, there's Keto for Neuro on Facebook, where members have some neurological diangosis/condition, including brain injury.

Electrolytes (and their ratios) and water are huge as the body excretes them quickly. So look into fairy/electrolyte dust by this site, which I like though they promote lots of dairy, which is not good for all people and has to be of good quality (or as good as a person can afford). Do not overdo electrolytes either. I had way too much pink salt my first go and I think that contributed to my kidney pain.

Vitamins and supplements for Keto - Impulsive Keto

I did read a story on a TBI/PCS Facebook forum that a lady had rather severe symptoms after a TBI, was diagnosed with Alzheimer's, put on meds, tried loads of therapies, but is now symptom free after going and staying keto. Pretty neat.

There's lots more out there for info, including supplementing with something like MCT oil (only get C8/C10 triglyecerides if you do) or ketone salts, but I don't want to overwhelm you and give you too much that you don't give the diet a shot.

Basically, keto increases lots of good things in the brain and body (antioxidants, BDNF, GABA, mitochondrial health, etc.) but it CAN go very wrong if people don't do it right (keto flu, kidney stones, etc.)