Sphenopalatine ganglioneuralgia. The chances are very likely that you’ve experienced this. It is a common malady brought on by a desire for pleasure that results in pain. Sphenopalatine ganglioneuralgia is the medical term for a cold-stimulus headache, also known as brain freeze or ice-cream headache. It is caused by intense cold touching the roof of the mouth resulting in nerve response causing rapid swelling and constriction of blood vessels. It is not pleasant . . . as the reader probably knows.
If a novelist wishes to have a character experience an ice-cream headache, that can be all well and good. My counsel would be to not use the unpronounceable medical term for it . . . at least not unless the writer explains what it means and includes it for a specific purpose that adds to the story. (For instance, a character might be a medical student who repeatedly tries to impress others with his or her medical knowledge and vocabulary.)
For writers with a love of words and a rich vocabulary, there is a temptation to use words that simply bamboozle the general public. An awareness of this danger does not mean one should dumb-down one’s writing, but it should motivate one to consider the purpose and appropriateness of vocabulary choices. Learning new words can be an appreciated part of the literary experience for readers, but it can also be overdone by an enthusiastic author.
Example. One might describe the atmosphere in a room as mephitic, but few people know what that word means . . . or would ever use it in conversation. Why not call it simply foul-smelling or malodorous?
Professional wordsmiths have a ball with language. Amidst the fun, discretion is also a virtue.