That Word?

What's that word that describes an impending explosion in your head? It starts out maybe as a slight headache, a minor throbbing. Maybe there's a minor vertigo effect. Then it stops and you think you may be fine. But it starts up again. You feel your brain pulsating, pounding the walls of your skull. The pain intensifies to the point where you can't do anything.

What's that word?

I've got less than 10 hours before I finish my first complete draft of my dissertation. I still have to do some editing and grammar checks before I send it off. Come to think of it ... I just remembered I have to fix my conclusion now that a major portion of it went into the introduction.

Seriously, what's that word I'm looking for?