Ordinary curcumin does have poor bioavailability. However, there are various formulations or additives that measurably increase bioavailability. Classically, pepper (e. g. bioperine) is added and achieves marginal improvement. It's cheap and extremely common.

Theracumin is a nanoparticular form that is significantly more bioavailable. I purchase this for myself. (I don't have a TBI or PCS.)

Longvida is another additive that increases bioavailability. There's some study that shows curcumin with Longvida crosses the blood brain barrier. I personally purchase Now Foods Curcubrain for my brain injured fiance.

Meriva is another additive shown to improve bioavailability. I want to say I read it's much better than pepper, but not as effective as Theracumin or Longvida.

I am not aware of any scientific study comparing the bioavailability of each, but I did read a site awhile ago analyzing what data is available and drawing the conclusions I mentioned above.