Welcome to neuro Talk, Sorry to hear of your father's struggles.

From what little I know about comatose TBI subjects, I do know one thing. It is beneficial for him to hear familiar voices. Keep talking to him. Some people have gone so far as to read to their loved one.

Does he have any favorite books or authors? Did he always read the newspaper? Anything familiar read by a familiar voice will be good.

Anything you can do to stimulate his senses will help his brain find its way back. Massaging his hands while you talk to him.

Hopefully, his doctors and other health workers have explained these to you.

Your road ahead will likely be a long one. I have a friend who was comatose for 6 weeks and took 2 years to regain his speech and walking skills. Your efforts may seem fruitless but don't lose hope. Every little bit help him move forward in his recovery.

My best to you.