It all starts with an innocent spoonful of ice cream. Then another. Then another. But before you know it, your ice cream sundae — or perhaps morning smoothie — has stopped you cold in your tracks with an old fashioned case of sphenopalatine ganglion neuralgia — better known as brain freeze. It’s so common, you could ask if it’s really even summer without experiencing this sensation. It’s not harmful and it doesn’t last long, but when it hits, those few seconds can be crippling. So what causes it?  After many personal experiments diving face first into that mint chocolate chip cone, you already know that cold treats leave you with a quick and intense headache. But what causes our bodies to react that way? Is it really cold temperatures “freezing” your brain? “On the roof of your mouth you have this thick bed of capillaries, so when you have something cold, it causes…