I think that you can trust that you don't have a brain tumor based on your half of an MRI (no, I am not a doctor nor do I play one on TV
) - I suffered a major sinus infection in 1995 and was sure I was dying of a brain tumor - vertigo, sleepiness and a myriad of other symptoms. I was sure it was that or MS. I had an MRI and it finally put that fear to rest. Unfortunately, that entire episode was enough to create an anxiety-ridden way of thinking that I now live with daily.
I think you have enough reassurance based on your MRI to stop worrying about that. Just don't replace it with a new worry and don't symptom surf on the Internet - it just adds to the anxiety !