hi, i have had what i call spells about once per month since 2006.at first i thought i was dying and it became so frequent once per month that i kept a diary. i can tell it is going to happen before it starts.unable to discribe except it ends with sweat.it usually lasts 1,2 or even 3 days in a roll. it will happen in sleep,while eating,walking,sitting still with not a worry in the world.