"The last one I had in New Zealand. I was over there surfing with my family and my young bloke, we were out in the water for six or seven hours a day.
"I think about it now because the specialist said I can't surf on my own. I make sure I don't go out (surfing by myself)."
Johns retired from the NRL more than a decade ago but his first incident only occurred three years ago.
"I was calling a final between Canberra and Penrith down in Canberra in 2016. I was up there commentating and all of a sudden something came on in my body," he said.
"I went into this trance, this state, and I went into this dream. It's hard to describe, you go into this deja vu kind of scene and everything goes quiet.
"It hit me, and I came out of it and was just sitting in the commentary box and obviously I didn't say anything for a while. The producer came up and said, 'Mate are you all right?'.
"Later that night I went home to the hotel and went straight to bed, which is pretty much a first … I woke up in the morning and had two big puncture marks in my tongue and it had swelled right up."
Johns sought medical advice and two professionals told him it was likely a form of epilepsy, potentially caused by multiple concussions.
"They can't be sure what causes it. It may be something that just pops up later in life," Johns said.
"But they think maybe a contributor could be some of the concussions I've had, and some of the continual head knocks."
Proving he is only human after all, at least off the footy field, Johns also said he did what is often the worst possible thing — he Googled his symptoms.
"I was scared before I had these final scans, because when something goes wrong you Google it and it comes up with the worse case scenario," he said.
"But the doctors and professionals I've seen have said my medication level is right, you can live a normal life."
