Oh hello pinkpercy :)
Well, it's past my bedtime and I am no expert but here's what wiki says "Neuropathology is the study of disease of nervous system tissue, usually in the form of either small surgical biopsies or whole autopsy brains. Neuropathology is a subspecialty of anatomic pathology, neurology, and neurosurgery."
So, being pedantic, I would say "study of the diseased tissue, rather more than the disease generally" but the person whose tissue was being studied would not necessarily have to be dead. Oh I hope we don't have nightmares. Long time no speak. Hope you are well. Merry Christmas to you xx