Ive mentioned before in other videos that when he talks it seems as though one side of his mouth/face moves normally and the other side it seems is kind of stiffer.
I think he's always had this mouth thing, but it's just become more pronounced over the years. I was watching some interviews of him from the mid-late 90s, and he was starting to do it then. I don't know that it's related to whatever else is going on. I'm not a doctor though.
There's been tons of speculation on here as to what's causing Scott to talk/look/move the way he does, and who knows how close people are to the truth. Personally, my guess is that he's still using painkillers or maybe other pills like benzos, and mixing things that shouldn't be mixed (benzos, painkillers, liquor, bi-polar meds). I know Scott says he hasn't used "drugs" in 13 years, but I think when he says "drugs," he's only including heroin and maybe coke.
Rob said this in 2010 before the S/T tour: "He can't got on tour. He needs help… He thinks he's clean just because he's not shooting heroin. But he's popping pills."
He seemed to be in decline through 2011 and 2012 until the breakup and then there was the Purple to/at the Core Tour, which was mostly awful. He tried to make Doug take the fall for that, but maybe the real reason was that Doug was starting to stand up to Scott and stop enabling him. Then, Danny Thompson quit, rejoined, and quit again, citing "a matter of self-worth" and "the Darkness" as his reasons. Then, Jeremy Brown dies of multiple drug intoxication. Then, Corpus Christi happens, followed by a series of bizarre interviews and Meet & Greets where he's rude to fans.
I think it's eventually going to come out that he's still been abusing drugs this whole time -- whether that be prescription pills or otherwise. And it's obvious he's been drinking a lot this whole time. Whether or not that's a problem by itself, you be the judge, but bad things happen when you mix alcohol with other shit (speaking from experience here). I don't even think he's convinced himself that he's not using -- I think the "13 years clean" line is just to keep the "asshole media" at bay, and there's just barely enough truth to it that he can say it with a straight face. The rest of it, I think he's trying to keep covered. I think he's surrounded himself with people who understand to varying degrees that this is how he wants to live (Tommy, Nick, his wife even?), and they are there to support his lifestyle and help keep the ship afloat. Then, there are people who've grown tired of his shit and refuse to work with him anymore but won't speak out about his problems without being highly cryptic and non-confrontational, maybe because they feel it's not their place and they don't want to rock the boat (Doug, Danny, VR). Finally, there are the people who call him on his shit (Deleos) -- even with them, there's only so much they're willing to say; a lot has been kept in secret, away from the fans and the public.
(Note: I'm not saying the Deleos have been perfect -- even with all the shit Scott's pulled, I still think the lawsuit was in bad form. I know the purpose was for them to continue with CheSTP, and I supported CheSTP, but now that that has ended, I think it makes their whole play to sue Scott and replace him in STP look even worse.)
Again, no one knows the truth, and I know the Scott apologists on here are going to jump on this and start spinning it how they want. But when you really look at the events of the past several years, it seems painfully obvious that Scott is still struggling with addiction in a big way.