My son was born wit a rare neurological syndrome at 18 months after I read a news article and researched the issue (I knew he wasn't meeting his milestones, but the news article fitted him and our circumstances exactly).
His syndrome is an umbrella syndrome for lots of other neurological issues that are wide and broad and the symptoms can be variable.
At 5, we were increasingly concerned about some involuntary movements he seemed to be making and at out next hospital appointment I said I had looked into it and thought he was having myoclonic seizures and asked if he might have Juvenile Myoclonic Epilepsy. The registrar dismissed it saying that he was too young and it was probably a tic and we needed to wait a year to see if he would grow out of it.
Because he had recorded it as a tic, despite not witnessing one, no one else would contradict him and they became intransigent about it. They wouldn't do any tests. We decided we would pursue a second opinion and paid for an appointment to see a paediatrician in London. He referred us to Great Ormond Street (privately) for a EEG, which showed myclonic seizures and absence seizures in large numbers. He diagnosed JME and wrote back to our local hospital.
They sent us an appointment within days and when we attended they apologised profusely and organised an MRI which showed that the two halves of his brain didn't fuse properly at birth, and confirmed the diagnosis of JME. They acknowledged that as parents we had done the research that they hadn't because the syndrome is so rare ( or underdiagnosed!)
JME and the gap in the brain are also symptoms within the umbrella syndrome.
They have never refused to pursue an investigation for him since.
I don't regret pursuing the private option, but regret that it was necessary and am well aware that not everyone has that option. I also regret that he was having so many seizures for so long without medication - at his worst he was having 40 myoclonic seizures a day. Currently he has none!