Blackouts
I had one of these in 2009 whilst in Holland and woke up in an ambulance, after extensive and inconclusive testing the CAA still require me to undergo even further testing at personal expense before they will consider renewing my class 2 medical and even if these further tests are negative I will have to fly with a safety pilot for an unknown period of time.
Personally its not worth it for a pplh so my helicopter flying days are over.
I know one other Class 1 medical holder who experienced something similair again with negative test results and that was the end of his flying career so I hope that you fare better.