Zeller, a science journalist, does not get migraines. He suffers from something generally acknowledged to be even worse: cluster headaches. Often featuring in lists of the most painful conditions in medicine—along with trigeminal neuralgia, sciatica, and gout—cluster headaches are named for the way that they descend in clusters, several times a day. The intensity of the pain is reflected in another name for the condition: suicide headache. Zeller describes the pain as “white-hot, blinding but invisible, frantic but elephantine” and writes of “writhing on the bathroom floor; of spittle and drool; of fingertips ground furiously into the scalp in a futile attempt to soothe whatever shrieking complex of anatomy is tearing at the right side of my head.”