My daughter was 9 months old when attempting to crawl up a stair she slipped and banged her head. She became pale and floppy for just a few seconds and recovered quickly. I wondered if I had imagined it. By the time she could walk and was playing with friends I had almost forgotten the incident. When one of those friends took a toy from her, her response was a typical toddler scream. To my horror this was followed by a sudden collapse to the floor and a few seconds of unconsciousness. I headed straight for my GP who told me he thought this was breath holding. I didn’t feel it had been a conscious holding of breath, rather an involuntary collapse, but even though I was a nurse I found myself accepting his assessment—it was a diagnosis I could live with and I didn’t want a series of distressing investigations.

The “attacks” as I called them, because they came without warning and Frances was unable to control them, came about once or twice a year until she was 9 years old. I began to see that they had various factors in common. Frances would often be excited when they occurred, as when playing chase with Dad; …