I was five or six, growing up in London, when the first strange episode occurred. Waiting to fall asleep, I suddenly felt as if my bed was enormous and I was tiny, and unable to move.

This sensation recurred a number of times. I remember telling my mum and her saying: “Oh, you were just dreaming.” But I thought: “Then why am I having this dream again and again, and why does it seem so real?”

Then there were times when I passed out. Once, I was in the middle of my English literature O-level exam – it was probably the most mortifying thing that had happened to me up to that point. English lit was one of my favourite subjects and I should have achieved an A or B grade. I ended up with a D and wasn’t allowed to retake.

It was around this time, at the age of 16, that I was diagnosed with temporal lobe epilepsy, now more commonly referred to as “absence seizures”. It didn’t cause me to shake or fit, just to zone out for a few seconds. But the specialist couldn’t account for the more bizarre manifestations. If I was with people, I’d start to feel disconnected from them, and begin to feel as if I was watching myself on television. Then it felt like my hands and arms would start to grow, and as they expanded, the room seemed to close in on me.

I’d be convinced my arms had expanded to the size of an elephant’s leg. When I looked at them directly, I’d see that nothing had changed, but my brain remained convinced they were huge, and they wouldn’t function as they should – I couldn’t pick up a cup of tea, for example.

It was as if two sides of my brain were arguing with each other. The rational side would be saying: “Your hands are not massive. You can ride this out.” But the other side would retort: “Yes, they are. You can’t move. You can’t do anything.” My heart would beat faster, I’d be unable to concentrate on anything else that was going on and at times I’d start to sweat.

After a few minutes – though it could feel longer – things would return to normal. I learned to remain calm, but the episodes sometimes struck at inconvenient moments. Once, I felt one coming on just as my boss asked to see a work-related Instagram post on my phone. I slowly began to sense my hands growing; I wasn’t able to touch the phone screen because my fingers seemed bigger than the phone itself. I couldn’t speak, either. Luckily, my boss’s phone rang at that moment and she walked off, giving me time to wait for the episode to pass.

The condition seemed to strike more often at times of stress: when I was organising my wedding; after my dad had a stroke. I tried not to let it affect my life – I’d occasionally miss my stop when travelling on the tube, but never felt my life was in danger. Then in 2016, at the age of 48, I saw a new consultant, the first not to dismiss my descriptions of the more bizarre symptoms.

“Ah,” he said, “that sounds like Alice in Wonderland syndrome.” He explained that it was a rare neurological disorder that temporarily distorts the way you perceive your own body or the world around you. He said there were a number of possible causes, including epilepsy. It was such a relief because it confirmed that I hadn’t been making it up and that I wasn’t alone – it happened to other people. I found a chat group on Facebook about the condition, which helped me to understand it better.

The name of the condition – also known as Todd’s syndrome – makes sense, given that Alice grows and shrinks in Lewis Carroll’s books, but people’s experiences of it vary. Distorted body parts is a recurring theme; others have reported seeing animals that aren’t there, the faces of those around them changing, or perceiving time moving faster or slower or standing still. I understand it’s mostly children who are affected, and they generally grow out of it – in continuing well into adulthood, my case seemed particularly unusual.

I told hardly anyone of my diagnosis – those I did tell sometimes seemed to think I was making it up, or even laughed. Since my epilepsy medication was tweaked in 2019, I’ve had no further episodes. I’ve learned to live with the likelihood they might return, though, and next time I’ll be ready.

• As told to Chris Broughton

Do you have an experience to share? Email experience@theguardian.com

Comments on this piece are premoderated to ensure the discussion remains on the topics raised by the article. Please be aware that there may be a short delay in comments appearing on the site.