Thunderclap headaches are a “genus” not a “species.” Pathologies are often part of larger, more diverse groups than we know.
We often make the same mistake with critters! For instance, the anglerfish is not just one mean-looking species, but a family of hundreds (hat tip to Cara Santa Maria, who talked about this on a recent episode of The Skeptics Guide to the Universe).
Thunderclap headaches are one of my own chronic pain demons — indeed, probably my single worst symptom. The specific cause remains undiagnosed. A neurologist once overconfidently asserted that we’d already eliminated the “only possible serious cause” of my symptoms. O rly? 🤔 Please see Devenney et al.!
My huge guide to headaches describes several other primary headaches — migraine, cluster, exertional, hypnic, and so on — plus a whole bunch of secondary headaches.