SUMMARY: Clarifying that brain tumor most likely cause.
Although I thought I was clear in my email/blog post that the tests had eliminated most possible causes (including goodies) of Jake's seizures except a nodule or tumor on the brain, several people have asked about the goodies. The emergency clinic did quite a panel of blood and urine tests on Jake right after the first seizure, and everything was normal. This ruled out some causes of seizures, such as hypoglycemia, liver disease, or kidney failure. Xrays showed nothing odd in the stomach like lead fishing weights that could have caused sudden lead poisoning. I was able to provide the vets with the torn-up packages that Jake got into, and they said that there was nothing in the ingredients that would cause seizures even in quantity. As far as I was aware, there had been no trauma to his head at all to cause swelling, another possible seizure cause, and there were no symptoms of concussion, edema, or encephalitis. And no signs of heart problems or tumors, which could also have caused seizures.
Most likely at his age, they concurred, it would be a brain problem, and not even most probably a stroke but more likely a tumor or other nodule or growth in the brain. They considered that his brief stroke-like symptoms--having trouble standing--two weeks ago today was much more likely related than was his goodie fest. Furthermore, his main post-seizure symptom--pacing steadily in one-directional circles--is very typical of a brain tumor on that side of the cerebral cortex. And he had been drinking prodigiously all day, which could have been related to the goodies but I think he'd been doing it beforehand, too--don't remember--and that's another symptom of brain tumor.
I followed up with some reading on the internet, and nothing I found contradicted these opinions (which two emergency room vets and my own vet all agreed on). Basically, any one thing could point at several causes, but put everything together, and the brain tumor seemed most likely.
At 15, and with the seizures coming quickly, lasting forever (in excess of 3 minutes each) and miserable confusion and loss of self combined with horrible despairing yowling any time we tried to get him to hold still or confine him, lasting for hours after each, it seemed pointless to do more diagnostic tests. If we had confirmed it was a tumor, we could have put him on constant antiseizure meds, with no guarantee that they would work. If it wasn't a tumor, we could have spent ages doing more tests, also using antiseizure drugs, and maybe or maybe not coming up with an answer. I just couldn't bear to put him through any more of what he'd been through.
A little further reading on seizures in dogs: