Will weed hurt my brain if I am recovering from a very traumatic brain injury?

Yes. Weed is harmfull whether you injured your brain or not. Never use weed.
I forget? Don't need to be a scientist to knwo cannabis (thc) impairs memory - even avid pot-smokers cheech & chong have immortalized a track about it on their up in smoke album. Studies show interference with verbal memory and learning, reaction times etc, and thc can be found in brains of heavy smokers 6 months after stopping. Probably not permanent, but it takes months to clear up - seen it in patients.
Yes. Brain has naturally occurring chemicals called "endocannabinoids, " that are secreted by brain for restorative purposes. The effects of plant cannabinoids are not the same. Mj will decrease blood flow to brain & hinder healing. Endocannabinoids occur naturally & don't have deleterious effects. There are experiments under way to find ways to enhance natural chemicals. Smoking weed isn't one of them.