It’s a typical morning in Bigmouth Towers. Baby Bigmouth has woken up an hour earlier than is fair or decent, and she’s dragging her dummy along the bars of her cot like a lifer in a maximum security prison. We get up, bleary eyed, and we hear the thundering of paws as Megan, Destroyer of Shoes, charges up the stairs to the baby gate, waiting for her chance to give Baby Bigmouth a good morning lick. As ever, I go to say hello to Megan, put on the coffee machine and have the first cigarette of the day.

But Megan isn’t at the baby gate. She’s on the sofa, flat on her back, jerking. Her mouth is foaming. I go over to her and she clearly doesn’t know who I am or what’s happening to her, and she bares her teeth and does the kind of barking you see on TV programmes with titles such as “when good dogs eat kids”. Something weird is happening, she thinks, and that baldy bloke is responsible. If he gets any closer I’ll eat his face.

I shout up to Mrs Bigmouth, “don’t come downstairs”. I grab the mobile, go outside and call the emergency vet number. They tell me that Megan’s having a seizure. She’ll be okay in a bit.

Sure enough, by the time the call is over Megan’s at the back door, sad eyed. I let her out and she immediately nuzzles into me, desperate for affection. I reassure her that everything’s OK and try not to blub.

I Google. It could be poison – Megan loves diving into gardens and chewing things she shouldn’t, and this is weedkiller, pesticide season. We make sure anything we use is kid- and pet-safe, but other people might not. Megan’s been sick, it might be that. It could be a reaction to a bite, or some rubbish she’s chewed when we weren’t looking, or something in the water when she was trying to drink an entire stream.

We go to the vet. Heart, temperature, other things, all okay. It’s epilepsy, the vet tells us. No cure. If it happens again, which it probably will, we’ll need to put Megan on phenobarbitol. Unfortunately that’s really bad news for her liver, so we’ll have to give her more meds to deal with that. It’ll probably take a few years off her life, too.

The thing is… if she’s got epilepsy it’s idiopathic epilepsy, which can’t be detected: it’s a process of elimination, the diagnosis when everything else has been ruled out. Yes, the vet did temperature, listened to her heart, but they didn’t do blood tests or anything else. The appointment was 3 hours after the seizure, so any symptoms from things such as poisoning may have been and gone by then. I don’t know. Those of you who have dogs – have you ever encountered a seizure that happened but didn’t recur? Or is the vet right in diagnosing epilepsy without checking in detail for anything else?