"Troll brain" refers to what happens when your testicles are side-by-side and are pressed firmly against the clothing covering your testicles; which will leave you with a "troll brain."

It's the sweat that accumilates under big boobs

A rare internet troll.
A trollbrain uses more coherent posts or spam than regular trolls.
The greatest weakness of a trollbrain, and the main factor that sets it apart from a troll, is that it has the ability to feel pain due to flames.