Thought I'd post this as I wasn't aware this was possible in dogs, but mine is about a week into treatment. She's a 2 year old fell terrier.
2 Friday's ago we were out for the tea time walk. Dog was full of energy, running and retrieving like a good un. At her dinner fine then had a nap. All as per usual. Normally she would wake at about 19:30 and want to play for half an hour, but not tonight. She appeared knackered and slept all night.
At 05:00 we awoke to hearing her having a seizure. It lasted about 60 seconds. Surprised and a bit worried we took her to the vets at 08:30. They suspected epilepsy but really there wasn't much to do at this stage. The dog was lethargic but had an appetite. What followed was a rapid decline. She had another 4 seizures before 13:00 that day and she was into the emergency vets that afternoon and kept overnight for monitoring.
She he was given Valium and had no more fits, but wasn't recovering. We took her back to the vets on Monday night and he would have expected her to have recovered but was concerned that she hadn't. For comparison, she was behaving like our previous 17 year old dog the week before we had her put down. He suspected meningitis and she was booked in the following morning for a spinal tap.
Long story short, he was right. She was prescribed a strong and long (6 weeks) course of steroids and the change after the first 24 hrs was amazing. She still isn't back to full fitness yet, but is at about 90%. If he hadn't spotted it so early there is a good chance she wouldn't be here given the rate of decline.
If this helps one of you spot it early then I'll be happy.
All the best