The difficulty with agreeing this evidence is that presumably the medic didn't appear in court to give evidence and so could not have been asked the obvious question: what else was consistent with such a blood clot, e.g., a fall or other accidental blow to the head? I don't know anything about your case and the circumstances whereby that evidence was agreed but your specific instructions should have been sought about this. I'm not sure that I would have agreed this from your narrative. You may want to seek an explanation from your solicitor directly as there may be a reason. I just don't see it from the information you have given. I hope that gives you a way forward. Please leave a positive rating so that I am credited for my time.
I really don't think he could as he proceeded to take the case to trial. It is a strange situation.