One of my sons has epilepsy. He's an adult now, so I try (and fail) to step back and let him and his doctors take care of things, because, well, he's an adult and he has to learn to manage his condition just like he has to learn to do a thousand other things adults do. But along the way I've learned some things about epilepsy and seizures. So when I saw the video that claimed Clinton was having a seizure and was injected with diazepam (trade name Valium) by an aide, parts of my brain started screaming in protest.
I'm going to try to avoid politics here. I'm also not going to address the claim that this aide, or Secret Service agent or whatever other function he had, has not been seen since, because I don't know if that claim is true or not, or if it is true what the reason is. I'm just going to focus on the alleged seizure and the claims of an injection of diazepam.
1. Let's start with the biggest problem: that doesn't look like a seizure. That looks like she's focusing on something happening in the audience, out of range of that particular camera. There are many kinds of seizures, but one thing you can't do when having any one of them is *focus*. The Clinton campaign says there was a protester in the audience, a story that fits her behavior better than the claims of a seizure.
2. The man who comes up and stands next to Clinton briefly touches her back. This is when the makers of the video claim he injected her with the drug. From our point of view, her clothing doesn't appear to move. So either this man is such an expert that he can lift up her clothes in the back, give her an injection, and replace the clothes, one-handed, in a matter of seconds, with no sign of anything happening from the front... or the auto-injector has a needle long enough and powerful enough to go through her suit jacket and blouse.
3. Clinton doesn't react. You know what it feels like to have a needle inserted into you, now imagine it being driven in at speed. And yet, she doesn't flinch or appear startled. She also doesn't show any signs of being discombobulated or even mildly confused when she comes out of the alleged seizure.
4. Diazepam would never be given to someone who had a single seizure. It's used for a condition called status epilepticus, which means either the person is having a single seizure that lasts for five minutes or more, or they're having repeated seizures without coming back to themselves in between. For that particular situation, diazepam can be a miracle cure, even life-saving, but it also has serious side effects. You're introducing a huge dose of brain-altering chemicals, after all. (Incidentally, in spite of the name, most people who experience status epilepticus do not have an epilepsy diagnosis or a history of seizures. It's a sign of something else going very wrong in the brain.)
5. Because some people are known to be at risk of status epilepticus, there is an auto-injector of sorts for giving a dose of diazepam when needed. But it's not like an Epipen. The drug is in the form of a gel meant to be inserted rectally. As in up the butt. There is just no way the man who supposedly had the syringe could have accessed that part of Clinton's anatomy without anyone noticing.
So either Clinton is suffering from a previously unknown type of seizure, and her doctor recommended a dangerous drug therapy for the first sign of any seizure, and prescribed this in the form of an auto-injector or syringe treatment not available on the open market, and this found its way into the hands of a man with unusual injection skills -- or something much more mundane is happening. I suggest there's a protester or heckler in the audience and the man who comes to Clinton's side is concerned about her safety, nothing more.
There are a lot of old misconceptions and superstitions about epilepsy - we should be fighting them, not using them as political weapons.