I'm a Physician, once afflicted with cch, and subsequently with hemicranium continua. I have been headache free now for several years. The cluster spells were discovered to be caused by either carbohydrate binges, or carb fasting. The common denominator being hypoglycemia. Nocturnal hypoglycemia occurring around 4 a m. And accompanied by nightsweats, sometime vivid night mares, and a severe hangover the following day. Hemicrania is not correlated w obvious hypoglycemia, but is relieved with routine daily indocin. When I was placed on metformin for blood sugar stabilization they disappeared. I've found that carb moderation through the day prevents all migrainous headaches. 1-2 grams of carbs per lb pound body weight per day should prevent cluster when spread out thru the day.