Hello dear friend, Please accept my concerns for you.You mentioned that it is occasional,that you tend to have such episodes.Please make it clear about a few points- 1) what is the frequency of these episodes,ie,once in a week,once in a month or once in a year and likewise. 2)How long does each episode last? 3)Are there any triggering factors for your episode-may be anything,cheese,coffee,smoke,stress,sunlight,lack of sleep.If you dont know yet,try to watch out if there is anything associated? 4)Do you have any abnormality in vision,during these episodes?-like reading half words,seeing star like things ,shimmering or flashing lights,light in a zig-zag fashion? Closest possibility if any of an organic cause in your case can be of a migraine variant and to rule out the same,i asked you the above questions.If I would have been your treating physician,i would have asked you to get a contrast enhanced CT scan done to rule out any structural abnormalities,still.You can discuss the possibilities,accordingly, with a neurologist.I hope it helps you.