Evan suffered seizures, but medics thought he was just holding his breath during tantrums. Desperate to get a proper diagnosis, Evan's mum Cerys, 33, a civil servant from Swansea, filmed one of his seizures and posted it onto her Facebook page, asking, "Does anyone know what this is?"
One of her friends quickly messaged that it looked like a rare condition called Reflex Anoxic Seizures, which can be trigged by pain or a fright, and causes the heart to slow down or even stop altogether.
Cerys and husband Rob, 35, took Evan back to the doctors, and he was confirmed as suffering from Reflex Anoxic Seizures at the University Hospital of Wales in Cardiff.
"It was terrifying when we didn't know what it was - he was having up to 17 seizures a day," says Cerys. "If I had not gone on Facebook we would still not have had a clue what was causing them.
"There needs to be more awareness. It's a very unknown condition. Facebook comes in for a lot of stick and criticism but if it helps one more parent like this it's worth it."
Doctors say Evan, now four, should grow out of his condition, but in the meantime, teachers at his nursery school know when to do if he has an attack, which can last 45 seconds.
"He will say afterwards that it goes black, and there is a buzzing sound in his ears," says Cerys. "He can either be very tired and clingy, or also very angry as he comes to understand what has happened to him. It's heartbreaking."
Jenni Cozon, head of patient services at the Stars, a charity which helps people with the disorder, said: "Sadly, Cerys is not alone in her struggle to find the correct diagnosis for her baby. Many children with RAS are misdiagnosed with breath holding."
You can see the footage Cerys filmed to post on Facebook in the video below.