It could be any number of things, but Thiaminase deficiency is one of the only ones where there is a potential treatment or something the owner can do (supplementing the necessary vitamin). It could be a protozoan ingested by eating gross petstore minnows has infested the brain and spinal cord and is now causing seizures, or it could be that heavy metal poisoning from a water supply is causing them, or maybe the snake isn't full grown and it has a congenital disorder that's just now showing up. It could be a infection, perforated intestine, failed liver, or any other condition that might allow toxins to build up in the body and affect the brain. But then again, most of those last ones should show other symptoms before it gets to that stage.

I have to agree with Steve, thiaminase is the easiest thing to blame given the history, but it's also the only one that the owner really has a chance to do anything about and maybe reverse or at least stop the damage being done. Even with that the outlook is bleak by the time seizures start up.

On that note: Am I just hallucinating there being a member a few years ago who got vitamin injections for a couple seizing ribbons and saw some success? I think maybe one died and one lived or something like that? It was near when I first joined, so I really had no clue what was up and don't remember it 100%.