TNF and migraine disorder: Further supporting the involvement of parenchymal inflammatory signaling in migraine without aura, elevated levels of IL-1β, prostaglandin E2, tumor necrosis factor-α (TNF-α), IL-6, and nitrite were detected in the internal jugular vein (which primarily drains the brain parenchyma but not the meninges) within the first hour of a migraine without aura attack [61, 104–106].