Unless Trump's doctor wants to rule out something specific, like a tumor or hemorrhaging, my guess is Trump is going through the normal aging process of brain shrinkage. It has a long medical name but that's what it amounts to. The neurologist would not usually discuss the results of the MRI with the patient, especially not in such grandiose terms. That's Trump's usual defense mechanism kicking in.
If the shrinkage is age appropriate, the neurologist might call the results "normal" with some explanation as to degree. It's up to Trump's doctor to decide treatment, if necessary, for the memory loss and perhaps balance that is associated with brain shrinkage. It gets worse with age.
You can forget any explanation from Trump. He would never admit that his giant genius brain is shrinking.
MTG's role as Trump's echo chamber in the House of Representatives has hurt a lot of people, including members of her own party, when Trump blew the dog whistle. And, like Trump, she did it with vicious gusto, even exceeding that of Trump's own.
I don't apologize for hoping she comes to a bad end . . . any more than I would for putting a rabid dog out of its misery.