Do you still have the ability to visit them, send them gifts, or notes, and telephone calls?
I don't know your situation but it sounds like you are saying your head injury made it impossible for you to parent your kids, through no fault of your own. It's just a matter of being unable to do the tasks required, although you want to.
Usually in cases like that, access is given to parents who want to continue a strong relationship with their kids.
Best wishes. This is hard.
another forum may be able to help you more, try the anxiety forum good folks there to help you, can you give them further info.this is a happy but hard time of year for many ,talking through it can help you .Good Luck