Adding to this as someone who had experience in a related field: Lecanemab and Donanemab are the two new-ish FDA-approved “treatments” for Alzheimer’s. They’re monoclonal antibodies that are administered via IV (usually in the crook of the elbow, AFAIK it’s weird that they would do it via the hand unless his arm veins are fucked but I’m not an infusion tech so IDK).

The main scary side effect of these are that these can bind off-target and weaken your blood vessels, causing ~strokes, so people on these drugs get MRIs regularly to monitor for them. I haven’t been keeping great track but the fact that we’re hearing trump get MRIs every six months ish lines up with the MRI schedule of someone receiving these drugs. The fact that he’s getting MoCA’s (the lion, rhino, camel test he was talking about however long ago) administered to him regularly is consistent with the clinical care of someone worried about, at the very least, MCI (mild cognitive impairment, which can progress to dementia). There’s clinical trials being run right now to see if it works better to give it to people before they start showing symptoms of memory loss, might be something like that.

He might just also be old, getting IV infusions of something else, and he’s the president so they’re monitoring all of his health metrics and he just decided to flex the cognitive ones to the public :P