With an inability to speak I expect some communication skills were under-utilized. I don't think you forget how to present ideas. I do however believe that with use, not only do you strengthen neural pathways, but you also become more proficient/ skillful. With time you will present ideas again automatically without the effort reserved for learning new skills (or re-learning old ones).
I think once you regain your confidence in your ability to speak and communicate ideas, you'll be fine. I think currently, the anxiety you feel over speaking is hindering you and your progress.
Stress and anxiety can cause one to become forgetful.
I think you should trust your ability to communicate. I also think you need to address the cause of the problem, which in my opinion, is the problem you have with your sinuses.
It's understandable that you would feel frightened. I think, trust yourself, practice speaking and forming ideas and reward or acknowledge when you do. Don't pressure yourself by setting unrealistic goals (it is a process and may not just happen instantaneously).
Follow up with a doctor about the pain and sinus issue.
Best wishes
J
You received some very good advice from Jaquta. I would only add that you start practicing to build up your confidence by talking to someone close to you who you trust and who is patient, and demonstrate to yourself that you can do it, then it will be easier in public.